GENETIC TRANSFORMATION OF PERENNIAL TROPICAL FRUITS
MIGUEL A.GO
′MEZ-LIM 1*AND
RICHARD E.LITZ 2
1
CINVESTAV Unidad Irapuato,Km.9.6Carretera Irapuato-Leo
′n,Apartado Postal 629,Irapuato GTO 36500,Mexico 2
Tropical Research and Education Center,University of Florida,Homestead,Florida 33031
(Received 17September 2003;accepted 10February 2004;editor E.C.Pua)
Summary
Genetic transformation provides the means for modifying single horticultural traits in perennial plant cultivars without altering their phenotype.This capability is particularly valuable for perennial plants and tree species in which development of new cultivars is often hampered by their long generation time,high levels of heterozygosity,nucellar embryony,etc.Most of these conditions apply to many tropical and subtropical fruit crops.Targeting speci?c gene traits is predicated upon the ability to regenerate elite selections of what are generally trees from cell and tissue cultures.The integrity of the clone would thereby remain unchanged except for the altered trait.This review provides an overview of the genetic transformation of perennial tropical and subtropical fruit crops,i.e.,citrus (Citrus spp.),banana and plantain (Musa groups AAA,AAB,ABB,etc.),mango (Mangifera indica L.),pineapple (Ananas comosus L.),avocado (Persea americana Mill.),passion fruit (Passi?ora edulis L.),longan (Dimocarpus longan Lour.),and litchi (Litchi chinensis Sonn.).Key words:avocado;banana;genetic transformation;mango;tropical fruits.
Introduction
Tropical fruits are important in the diet of people in less-developed countries,and are increasingly important as exports from many of these countries.Conventional breeding of perennial tropical fruit cultivars has been limited by their long juvenile period (up to 20years),low fertility,high levels of heterozygosity,various levels of ploidy,polyembryony,complex intraspeci?c incompat-ibility relationships,and severe inbreeding depression.Plant breeders often do not have access to adequate genetic diversity within local germplasm collections.Genetic diversity within many tropical fruit crop species is unexplored,and most cultivars are either seedlings from uncontrolled pollinations or dooryard selections.The production of many tropical fruit crops is based on a rather limited number of cultivars,which are poorly characterized for genetic traits.
Biotechnologies that could increase the ef?ciency of tropical fruit crop improvement are essential to generate improved cultivars with novel traits.For example,genetic mapping could provide breeders with the tools to make rapid progress in crop improvement.Functional genomics could provide insights into genetic regulation of plant function and novel means for isolating genes for manipulation in transgenic plants.Older biotechnologies,including somatic hybridization,in vitro mutation induction and selection,etc.,have rarely been applied to these tropical fruit species for crop improvement.These tools have only begun to be employed for many tree crops,and work with tropical crops lags far behind that with herbaceous species.Of the nearly 6000?eld releases of transgenic
plants in the USA from 1987to 2000,less than 1%(approximately 40)were fruit trees (https://www.doczj.com/doc/364865990.html,/biotech).
Genetic Transformation of Tropical Trees
The dif?culty in regenerating many tree species from elite or mature phase selections is one of the most serious obstacles for applying gene transfer technologies to these plants.In addition,few genotypes of a particular species have been transformed and,in many instances,these genotypes are not commercially important.Evaluating the performance of transgenic fruit tree cultivars requires approximately 12years or until fruiting and ?owering have been observed,depending on the species.Thus,molecular breeding represents a highly ef?cient approach for developing improved,perennial tropical fruit cultivars.The following discussion of tropical fruit crops outlines some of the research in progress,and is not meant to be an exhaustive review.Citrus (Various Citrus )
Citrus species are the most widely grown fruit,and world production exceeds 102600000Mt (FAOSTAT,2004).Breeding imperatives have focused on rootstock and scion cultivar improvement.Rootstocks should be tolerant of biotic and abiotic stresses associated with roots,show good graft-compatibility with scions,show polyembryony,and support good yields.Scion breeding has attempted to retain the characteristics of existing superior selections but with improved fruit quality,yield,disease resistance,earlier or later maturing fruit,etc.Breeding goals of fruit for processing and for fresh consumption are different.Application *Author to whom correspondence should be addressed:Email mgomez@ira.cinvestav.mx
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of biotechnology to citrus has recently been reviewed by Moore et al. (2004).
Genetic transformation studies involving citrus have been based upon organogenic and embryogenic regeneration pathways. Induction of citrus embryogenic cultures was described by Maheshwari and Rangaswamy(1958),and many later studies de?ned the optimum conditions for maintenance of embryogenic cultures and somatic embryo development(Kochba and Spiegel-Roy,1977a,b).The earliest citrus transformation experiments involved direct uptake of DNA into embryogenic protoplasts (Kobayashi and Uchimiya,1989;Vardi et al.,1990;Niedz et al., 1995).Particle bombardment was used to transform embryogenic suspension cultures of‘Page’tangelo(Yao et al.,1996),and Hidaka et al.(1990)described Agrobacterium tumefaciens-mediated transformation of embryogenic cultures.Cervera et al.(2000) characterized70transgenic Carrizo citrange plants and observed altered ploidy level,T-DNA rearrangements,and low uidA expression,possibly due to multiple inserts or transgene silencing. The current protocol has involved the transformation of cells in seedling stem pieces and regeneration of shoots from organogenic cultures.Moore et al.(1992,1993)transformed Citrus with A.tumefaciens EHA101containing pMON9793with npt II and uidA,and transformation of Poncirus trifoliata,trifoliate orange, using a similar technique was reported by Kaneyoshi et al.(1994). The recovery of transformed grapefruit plants has been described using A.tumefaciens strain EHA101with pGA482GG(Luth and Moore,1999)and strain C58C1with pBin35SGUS(Yang et al., 2000),both containing npt II and uid A.Pen?a et al.(1995a,b) reported ef?cient transformation of Poncirus￡sweet orange hybrid Carrizo citrange and sweet orange‘Pineapple’from internodal stem segments inoculated with A.tumefaciens strain EHA105with 35SGUSINT.In order to overcome poor rooting of transformed shoots,they were micrografted onto Troyer citrange.Bond and Roose(1998)transformed epicotyl segments of‘Washington’navel orange using A.tumefaciens strain C58C1with p35SGUSINT. Transgenic key lime was recovered by Pen?a et al.(1997)using A.tumefaciens strain EHA105with p35SGUSINT.The procedure required co-culture of stem pieces on feeder plates consisting of tomato cells on medium containing high auxin levels.The regenerated shoots were micrografted onto Troyer citrange seedlings.Yu et al.(2002)re?ned Agrobacterium-based transform-ation,and utilized epicotyl segments that were cut in half longitudinally to increase the wounded area of the explants.Ghorbel et al.(1999)transformed three citrus types using this procedure with A.tumefaciens strain EHA105(pBin19-sgfp),which contains a gene for green?uorescent protein(GFP).
Recovery of transformed citrus in the mature phase has been reported.Cervera et al.(1998)partially rejuvenated mature sweet orange by grafting buds onto seedling rootstock.Internodal stem pieces were inoculated with A.tumefaciens strain EHA105with p35SGUSINT,and then co-cultivated on tomato cell culture feeder plates.Some of the transformed regenerants?owered,and fruit were produced after14mo.In another study,Carrizo citrange was transformed to express the Arabidopsis LEAFY(LFY)or the APETALA1(AP1)genes,which promote?oral initiation(Pen?a et al., 2001).The regenerants displayed an abnormal phenotype,but plants expressing AP1had fertile?owers and bore fruit in the?rst year. Perez-Molphe-Balch and Ochoa-Alejo(1998)reported trans-formation of Mexican lime following inoculation of stem segments with a wild strain of A.rhizogenes containing a binary vector plasmid pESC4that contained nptII and uid A.Shoots were regenerated directly or from the hairy roots.
Genetic transformation of Citrus has focused on enhancing disease resistance and improving fruit quality.Several groups have transformed citrus with the CTV-CP gene(Gutierrez-E.et al.,1997; Dominguez et al.,2000;Ghorbel et al.,2000)or with an untranslatable version of this gene(Yang et al.,2000).Cervera et al. (2000)transformed Carrizo citrange with the yeast gene HAL2, which seems to be implicated in salt tolerance.Yang et al.(2000) also transformed grapefruit with the Galanthus nivalis agglutinin gene,an insecticidal gene.A gene for a pathogenesis-related(PR) protein from tomato(PR-5)has been expressed in transgenic sweet orange,and regenerants showed increased tolerance to Phy-tophthora citrophthora(Fagoaga et al.,2001).
Banana(Musa groups AAA,ABB,AAB,etc.)
Bananas and plantains together are a major staple food crop of the tropics and the dessert banana is a valuable export commodity. The annual production of banana and plantain is approximately 69000000Mt(FAOSTAT,2004),and is exceeded among fruit only by Citrus.Most of the producers grow the crop(s)on a small scale for domestic consumption.
Fusarium oxysporum Schlecht f.sp.cubense(E.F.Smith)Snyd and Hans(Panama disease or wilt)and Mycosphaerella?jiensis Morelet(black Sigatoka)have spread rapidly throughout the major production areas during the past generation.Despite the importance of banana and plantain for food security,conventional breeding has been ineffective for addressing these and other production problems because all important Musa cultivars are sterile triploids.World production is based upon very few cultivars that have been vegetatively propagated for centuries;somatic mutations have provided the only genetic variability.The genome size is approximately873Mb or six times that of Arabidopsis thaliana (Arumuganathan and Earle,1991).
Genetic transformation of Musa has focused on disease resistance and the control of fruit ripening,particularly of the‘Cavendish’type of cultivars.Genetic transformation of Musa has been reviewed by Smith et al.(2004a),and can be achieved in several ways,most of which are based on manipulation of embryogenic cultures. Embryogenic cultures are usually induced from immature male (Shii et al.,1992;Escalant et al.,1994)and female?owers(Grapin et al.,2000).Cote et al.(1996)and Dhed’a et al.(1991)optimized conditions for maintenance and somatic embryo development from suspension cultures.
May et al.(1995)wounded the meristems of in vitro plantlets by microprojectile bombardment followed by co-cultivation with A. tumefaciens(LBA4404strain).Although transformed plants were regenerated,this procedure has not been widely utilized because of low transformation rates and chimeras.Other successful transform-ation procedures have involved direct DNA uptake into protoplasts by electroporation(Sagi et al.,1994)and particle bombardment of embryogenic cultures(Sagi et al.,1995;Becker et al.,2000).The most commonly used procedure has involved Agrobacterium-mediated transformation of embryogenic suspension cultures. Ganapathi et al.(2001)infected embryogenic suspension cultures of‘Rasthali’(ABB)with A.tumefaciens strain EHA105,and
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transformed plants were regenerated;this procedure has now been adopted by other groups.
Embryogenic cultures have been transformed with genes for resistance to banana bunchy top virus(BBTV)and banana bract mosaic virus(BBrMV)(Becker et al.,2000),i.e.,genes important or essential for BBTV replication and a gene encoding the BBrMV-CP. Several banana genes have been cloned(Clendennen and May, 1997;Medina-Suarez et al.,1997),including some coding for defense proteins(Clendennen et al.,1997),which should be useful for addressing disease problems.Banana has been transformed with genes encoding antimicrobial peptides,and extracts from leaves of transformed plants strongly suppress growth of Mycosphaerella ?jiensis(black Sigatoka)(Sagi et al.,1998).Musa has been transformed with genes coding for plant defensins(Broekaert et al., 1995;Remy et al.,1998).Bananas have also been suggested as an appropriate vehicle for edible vaccines(Mor et al.,1998)and bananas containing malaria epitopes have been generated and are currently in?eld evaluation(Y.J.Pen?a-Ramirez and M.A Go′mez-Lim,unpublished results).In other?eld trials of transgenic banana, delayed fruit ripening has been obtained using sense suppression of genes involved in ethylene biosynthesis(Balint-Kurti et al.,2001). Transformation of bananas has also facilitated the testing of novel promoters such as the constitutive banana actin1promoter (Hermann et al.,2001),and promoters derived from the BBTV DNA-1to25,which are expressed mainly in vascular tissue (Dugdale et al.,2001).
Mango(Mangifera indica L.)
Mango is one of the most important tropical crops,with world production of approximately26million Mt(FAOSTAT,2004), which is exceeded only by Citrus,Musa(bananas and plantains), table grapes,and apples.The species consists of two ecogeographic races that can be distinguished on the basis of their seed type,i.e., monoembryonic/subtropical and polyembryonic/tropical(Mukher-jee,1998).The rapid growth of the mango industry that has occurred in the past25years has largely been based upon modern selections of monoembryonic mangoes,i.e.,‘Haden’,‘Keitt’,‘Kent’, and‘Tommy Atkins’,which were identi?ed from(uncontrolled) openly pollinated seedlings in Florida,and now form the basis for the international trade of fresh fruit.Mango production in the humid tropics is often based upon polyembryonic selections that originated in South-East Asia,e.g.,‘Carabao’,‘Cambodiana’,‘Nam doc Mai’,‘Manila’,etc.
With very few exceptions,mango cultivars have not emerged from breeding programs(Iyer and Degani,1998).Mango breeding has not had a high priority,because it has been very dif?cult to achieve breeding objectives in an expeditious manner.The mango has a7-year juvenile period and the time required to evaluate seedling trees can be up to12years.The species is an allotetraploid (2n?4x?40)(Mukherjee,1950)with a genome size about three times that of A.thaliana(439Mb)(Arumuganathan and Earle, 1991).The frequency of fruit set has been estimated to be approximately0.001%(Mathews and Litz,1992),which is too low to permit manual,controlled pollinations.
Genetic transformation of mango has been based upon embryogenic cultures derived from the nucellus of young fruit (Litz et al.,1982;Litz,1984).DeWald et al.(1989a,b)and Litz et al. (1993)optimized the conditions for induction,maintenance,maturation,and germination.Genetic transformation of mango has recently been reviewed by Litz and Gomez-Lim(2002).Mathews et al.(1992,1993)transformed embryogenic cultures of‘Hindi’and of a‘Keitt’zygotic embryo-derived embryogenic line,respectively. These two studies utilized different disarmed,engineered strains of A.tumefaciens:strain C58C1containing the plasmid pGV 3850::1103with nptII(Mathews et al.,1993)and strain A208 containing the plasmid pTiT37-SE::pMON9749with uidA and nptII (Mathews et al.,1992)under the control of the CaMV35S promoter. Transgenic‘Keitt’plants were regenerated.Genetic transformation of mango has involved a two-step selection(Mathews et al.,1992). Only a single breeding objective of mango has been addressed using genetic transformation,i.e.,control of fruit ripening.Two cDNA clones,mango1-aminocyclopropane-1-carboxylate(ACC) synthase and ACC oxidase,have been identi?ed(Go′mez Lim, 1993),and a cDNA for mango alternate oxidase has been isolated (Cruz Hernandez and Go′mez Lim,1995).Cruz-Hernandez et al. (1997)transformed‘Hindi’utilizing A.tumefaciens strain LBA4404 containing pBI121with nptII,uidA,and each of the following: mango ACC oxidase,ACC synthase and ACC alternative oxidase cloned in the antisense orientation and under the control of the35S constitutive promoter.Since mango is a climacteric fruit, regeneration of plants in which ethylene production in mature fruit is inhibited could resolve the problem of premature ripening (jelly seed)and major post-harvest losses due to spoilage.
The feasibility for genetic manipulation of mango will allow the manipulation of fruit quality,the alteration of tree architecture, greater resistance to insect pests and diseases and the generation of parthenocarpic mango fruit(Yao et al.,2001).Some of these goals are being pursued in the laboratories of the authors.
Pineapple(Ananas comosus L.)
Pineapple world production is.14700000Mt annually(FAO-STAT,2004),and30%of the crop is exported either as fresh fruit or as processed products.Pineapple is native to South America and its center of origin is in the Orinoco and Rio Negro River basins.It has a diploid number of2n?2x?50(Brown et al.,1997),although triploid,tetraploid,and heteroploid cultivars exist(Collins,1960). The main objective of cultivar development is improvement of the processing cultivar‘Smooth Cayenne’,speci?cally with respect to nematode resistance,pineapple mealybug wilt virus resistance, resistance to fungal diseases(Espinosa et al.,2002),?owering,fruit ripening control,and blackheart resistance(Botella et al.,2000; Graham et al.,2000;Rohrbach et al.,2000).Although pineapple is a major fruit crop,there have been few molecular genetic studies, and very few genes been isolated.Much of the work involving genetic transformation of pineapple is proprietary,and has not been published.The current status of pinapple biotechnology has been reviewed by Smith et al.(2004b).
Pineapple has been transformed by microprojectile bombardment and by co-cultivation with A.tumefaciens.Nan et al.(1996)used microprojectile bombardment to transform embryogenic suspension cultures and obtained low-frequency transformation.Firoozabady and Gutterson(1998)and Isidron et al.(1998)recovered transformed plants from embryogenic cultures using A.tumefaciens. Graham et al.(2000)transformed‘Smooth Cayenne’leaf bases using A.tumefaciens,and recovered transformed plants from organogenic cultures.Espinosa et al.(2002)transformed morphogenic callus of
444GO′MEZ-LIM AND LITZ
‘Smooth Cayenne’with Agrobacterium strains AT2260and LBA4404and regenerated plants.Maize ubiquitin and CaMV35S promoters have been shown to function well in various pineapple tissues(Firoozabady and Gutterson,1998;Graham et al.,2000). The breeding objectives of pineapple that have been addressed using genetic transformation include disease resistance,control of fruit ripening,and control of blackheart disorder.Espinosa et al. (2002)described a complete protocol for transformation of pineapple with PR genes using A.tumefaciens containing constructs pHCA58and pHCG59,respectively.Plasmid pHCA58contained a class I bean chitinase gene under the control of a hybrid OCS-CaMV35S-rice actin I promoter(pA5)and tobacco ap24gene with the CaMV35S promoter.The plasmid pHCG59contained the chitinase gene under the control of the hybrid pA5promoter and a class I tobacco b-1,3-glucanase gene with the CaMV35S promoter. Plants were regenerated.
Although pineapple fruits are non-climacteric,both ethylene biosynthetic genes are up-regulated in the?esh of pineapple fruits during ripening(Cazzonelli et al.,1998,1999).An ACC synthase gene that may be involved in?oral initiation has been cloned (Botella et al.,2000),and its silencing in pineapple could suppress ?owering until it is induced arti?cially.This might facilitate synchronization of fruiting and ripening,and enable mechanized harvesting.Transformed pineapple plants containing genetic constructs to inactivate this gene as well as the ripening-related ACC synthase are under?eld evaluation(Botella et al.,2000). Blackheart is a fruit defect caused by exposure of pineapples to temperatures,208C,which stimulates polyphenol oxidase(PPO) activity.Stewart et al.(2001)cloned a PPO gene from pineapple fruits under conditions that produce blackheart.The PPO gene has been silenced in transformed plants and transgenic plants are under ?eld evaluation.
Avocado(Persea americana Mill.)
World production of avocados is.2800000Mt(FAOSTAT, 2004),and Mexico accounts for approximately35%of the total production.The international trade in fresh avocado fruit is very important,and Chile and Mexico are the leading exporters.The species is genetically heterozygous with a7–8-year juvenile period and high rates of?ower abscision and immature fruit drop.There are three races or subspecies of avocado:Mexican(subtropical), Guatemalan(highland tropical),and West Indian(lowland tropical). The chromosome number is2n?2x?24(Garcia,1975)and the size of the genome is about six times that of A.thaliana and similar to that of banana(883Mb)(Arumuganathan and Earle,1991). Major breeding objectives include resistance to Phytophthora root rot(PRR)caused by Phytophthora cinnamomi Rands.in rootstock cultivars,control of tree size,extended shelf-life of fruit, and development of a replacement for‘Hass’with many of the best qualities of this cultivar.Avocado breeding programs in various countries have been moderately successful,although cultivars have been derived from uncontrolled open pollinations.There are no genetic barriers among the avocado subspecies/races,and many cultivars are hybrids involving two or more subspecies.‘Hass’and ‘Fuerte’,which dominate world trade,are Guatemalan￡Mexican hybrids.
Genetic transformation of avocado has been reviewed recently (Litz and Witjaksono,2002;Litz et al.,2004c).Zygotic embryos (Pliego-Alfaro and Murashige,1988;Raviv et al.,1997;Witjaksono and Litz,1999a,b)and the nucellus(maternal)(Witjaksono et al., 1999)have been used for induction of embryogenic cultures. Conditions for optimizing growth of embryogenic cultures in suspension,somatic embryo development,and plant recovery have been de?ned(Witjaksono and Litz,1999a,b).Genetic transform-ation of avocado has been based upon highly embryogenic suspensions(Witjaksono and Litz,1999a,b).
In the?rst report,Cruz-Hernandez et al.(1998)utilized a two-step selection procedure,involving incubation of the putative transformed tissue in increasing concentrations of kanamycin.This study utilized A.tumefaciens strain LBA4044with binary vector pBI121containing nptII and uidA under the control of the35S CaMV promoter.Transformation of somatic embryos was con?rmed; however,plants were not regenerated.
The breeding objectives of avocado that have been addressed using genetic transformation include disease resistance and control of fruit ripening.In order to address some of the disease-related problems of avocado,embryogenic cultures have been transformed with various genes for PR-related proteins(Litz and co-workers).(1) Embryogenic cultures have been infected with A.tumefaciens strain EHA101harboring pHGAFP which contains the antifungal protein gene(AFP)together with uidA,the gene for resistance to hygromycin and the CaMV35s promoter.(2)Glucanase and chitinase have been cloned in pGPTV,together with uidA,bar (Basta resistance),and the CaMV35S promoter(Witjaksono, S.Raharjo,M.A.Go′mez-Lim and R.E.Litz,unpublished data). Transformed plants with the AFP gene have been regenerated,and are currently in greenhouse trials.In addition,a complex transformed somatic hybrid consisting of‘Fuerte’with b-1,3-glucanase,chitinase,bar,and uidAt‘Hass’with AFP,nptII,and uidA was selected on medium containing Basta and kanamycin sulfate,and plants(tetraploid)have been regenerated(S.Raharjo, Witjaksono,M.A.Go′mez-Lim and R.E.Litz,unpublished data). The regenerants will be screened as potential rootstocks. Avocado has also been transformed to extend the shelf-life of avocado fruit,and to extend the on-the-tree storage of mature fruit. Avocado fruit are climacteric.Fruit of Mexican,Guatemalan,and Guatemalan￡Mexican types do not ripen on the tree,and can be stored in this way for a few months(Whiley,1992).Tropical avocado fruit ripen on the tree,and have a poor shelf-life. Embryogenic cultures have been genetically transformed using A. tumefaciens strain EHA101with pAG4092harboring SAM hydrolase,a gene that blocks ethylene biosynthesis,in a construct containing nptII and under the control of an avocado fruit-speci?c cellulase promoter(Efendi,2003).Plants have been regenerated. Longan(Dimocarpus longan Lour.)and Litchi(Litchi chinensis Sonn.)
The litchi and longan originated in South-East Asia and southern China.The leading litchi-producing countries are China,Taiwan, India,Madagascar,and Thailand(Menzel,1992),and signi?cant production also occurs in South Africa,Australia,and the USA. Longan is important in Thailand,China,Taiwan,Australia,and the USA.Neither longan nor litchi has bene?ted from conventional breeding.There is little genetic diversity within germplasm collections of these species(Menzel,1992;Ding et al.,2001). The chromosome number of longan is2n?2x?30(Choo and
TRANSFORMATION OF TROPICAL FRUITS445
Ketsa,1992),and that of litchi is2n?2x?28,30,or32(Menzel, 1992).Trees are very heterozygous,and are vegetatively propagated.
Litchi and longan have not become major crops because of their relatively brief harvest period and the rapid decline of fruit quality and appearance after harvesting.The fruit are non-climacteric. Some of the important cultivars are very susceptible to anthracnose caused by Colletotrichum gloeosporioides Penz.,and chemical control is becoming unsustainable.Litchi and longan trees are irregular bearers,and high yields and regular bearing are necessary in order to exploit the potential of local and international markets. In China,the most valued litchi and longan fruit have small aborted seeds,known as‘chicken tongues’,a trait that is cultivar-related. Longan and litchi biotechnology have been reviewed recently(Litz et al.,2004a,b).
Somatic embryogenesis has been described from mature tissue of elite cultivars of longan(Litz,1988)and from zygotic embryos of litchi(Zhou et al.,1996;Yu and Chen,1997;Yu et al.,2000)and longan(Lai et al.,1998,2000).Conditions for optimizing maintenance of embryogenic suspension cultures(Lai et al.,1995; Yu and Chen,1998)and for somatic embryo development have been described.Zheng et al.(2001)transformed somatic embryos derived from longan zygotic embryos by inoculating them with the R1601 wild strain of A.rhizogenes.Secondary somatic embryos were induced from the hairy roots and transformed plants were recovered. Embryogenic litchi cultures derived from zygotic embryos have been genetically transformed with the antifungal protein gene (Witjaksono and R. E.Litz,unpublished data).Cultures were infected with A.tumefaciens strain LBA4404containing pBI121 with nptII,uidA,and the antifungal protein gene,with the CaMV 35S promoter.Although transformed somatic embryos were recovered,plants have not been regenerated.A major objective of longan and litchi transformation is the recovery of parthenocarpic fruit(Yao et al.,2001);however,a de novo regeneration pathway for litchi from elite selections must?rst be de?ned.
Passionfruit(Passi?ora edulis and https://www.doczj.com/doc/364865990.html,lis Sims f.?avicarpa Deg.) Passion vines are vigorous,wood-stemmed,tendril climbers,with a90-d juvenile period.Passion fruit is grown commercially throughout the tropics and subtropics.Brazil is the leading producer of the yellow passion fruit,https://www.doczj.com/doc/364865990.html,lis Sims f.?avicarpa Deg.,and 35%of Brazilian production is processed.The main commercial species and horticultural hybrids of passion fruit are2n?2x?18. Breeding programs have focused on https://www.doczj.com/doc/364865990.html,lis,the purple passion fruit,and https://www.doczj.com/doc/364865990.html,lis?avicarpa,the yellow form.The main breeding objectives include:(1)improved yield,(2)fruit quality,and(3) disease resistance.The most important diseases include Brown spot (Alternaria spp.),Phytophthora blight(Phytophthora ssp.),Fusar-ium wilt(Fusarium oxysporium f.passi?orae),Xanthomonas campestris pv.passi?orae,and passionfruitwoodiness virus(PWV). De novo regeneration of passionfruit has been by the organogenic pathway from explants derived from https://www.doczj.com/doc/364865990.html,anogenesis can occur either from callus(Mourad-Agha and Dexheimer,1979; Kantharajah and Dodd,1990;Monteiro et al.,2000)or directly from the explant(Kawata et al.,1995;Faria and Segura,1997;Otahola, 2000).Plant regeneration without a callus phase has been optimized for https://www.doczj.com/doc/364865990.html,lis?avicarpa.The application of biotechnology to passion fruit has been reviewed by Vieira and Carneiro(2004).
Transformation of https://www.doczj.com/doc/364865990.html,lis mediated by A.tumefaciens has been reported(Silva,1998;Hall et al.,2000).Agrobacterium tumefaciens strain1065,carrying uidA and nptII,has been used to infect leaf and root segments.Manders et al.(1994)utilized A.tumefaciens strain GV3111SE with pMON200that contains nptII,and obtained transformed plants.Stable transformation of passion fruit with nptII and uidA has also been described by Silva(1998),who used the LBA4404strain.
The primary breeding objectives that are being addressed using genetic transformation include resistance to bacterial and virus diseases.Particle bombardment has been used to transfer the bactericide attacinA gene driven by the35S–35S promoter to yellow passion fruit(Vieira et al.,2002),with the objective of resistance to X.campestris pv.passi?orae.Braz(1999)transformed passion fruit with a sequence derived from the replicase and capsid protein(cp)genes isolated from PWV.Preliminary results suggest that this strategy can be used to control this virus disease.
Conclusions
Genetic transformation of perennial tropical fruits has generally depended on embryogenic systems,and therefore regenerants of the woody species,i.e.,mango,avocado,longan,litchi,citrus,etc.,must pass through a period of juvenility before they can be properly evaluated.The two alternatives that have been utilized to overcome this limitation include:(1)invigorating plant material through grafting of mature buds onto juvenile stock plants(Cervera et al., 1998)and(2)constitutive expression of either the LEAFY or APETALA1genes from A.thaliana to shorten the juvenile phase and promote precocious?owering(Pen?a et al.,2001).Both of these innovations could stimulate more transformation attempts with these species.
The major hindrances that have stymied genetic transformation studies with tropical/subtropical fruit,however,concern lack of regeneration protocols for elite(mature phase)selections,e.g.,litchi and many tropical/subtropical fruit and nut species not included in this review,and the relative absence of molecular studies involving species other than citrus and bananas.The latter re?ects the state of the science in many developing countries where these fruit crops are grown on a large scale and the relative severity of production and post-harvest problems of the crop.Biotechnology studies involving fruit crops everywhere are generally underfunded,and national and international agencies should perhaps consider more support for research with these plants.
Acknowledgments
M.A.G.-L.gratefully acknowledges?nancial support from CONACYT.This paper is Florida Agricultural Experiment Station Journal Series no.R-10211.
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如何写先进个人事迹 篇一：如何写先进事迹材料 如何写先进事迹材料 一般有两种情况：一是先进个人，如先进工作者、优秀党员、劳动模范等；一是先进集体或先进单位，如先进党支部、先进车间或科室，抗洪抢险先进集体等。无论是先进个人还是先进集体，他们的先进事迹，内容各不相同，因此要整理材料，不可能固定一个模式。一般来说，可大体从以下方面进行整理。 (1)要拟定恰当的标题。先进事迹材料的标题，有两部分内容必不可少，一是要写明先进个人姓名和先进集体的名称，使人一眼便看出是哪个人或哪个集体、哪个单位的先进事迹。二是要概括标明先进事迹的主要内容或材料的用途。例如《王鬃同志端正党风的先进事迹》、《关于评选张鬃同志为全国新长征突击手的材料》、《关于评选鬃处党支部为省直机关先进党支部的材料》等。 (2)正文。正文的开头，要写明先进个人的简要情况，包括：姓名、性别、年龄、工作单位、职务、是否党团员等。此外，还要写明有关单位准备授予他(她)什么荣誉称号，或给予哪种形式的奖励。对先进集体、先进单位，要根据其先进事迹的主要内容，寥寥数语即应写明，不须用更多的文字。 然后，要写先进人物或先进集体的主要事迹。这部分内容是全篇材料
的主体，要下功夫写好，关键是要写得既具体，又不繁琐；既概括，又不抽象；既生动形象，又很实在。总之，就是要写得很有说服力，让人一看便可得出够得上先进的结论。比如，写一位端正党风先进人物的事迹材料，就应当着重写这位同志在发扬党的优良传统和作风方面都有哪些突出的先进事迹，在同不正之风作斗争中有哪些突出的表现。又如，写一位搞改革的先进人物的事迹材料，就应当着力写这位同志是从哪些方面进行改革的，已经取得了哪些突出的成果，特别是改革前后的．经济效益或社会效益都有了哪些明显的变化。在写这些先进事迹时，无论是先进个人还是先进集体的，都应选取那些具有代表性的具体事实来说明。必要时还可运用一些数字，以增强先进事迹材料的说服力。 为了使先进事迹的内容眉目清晰、更加条理化，在文字表述上还可分成若干自然段来写，特别是对那些涉及较多方面的先进事迹材料，采取这种写法尤为必要。如果将各方面内容材料都混在一起，是不易写明的。在分段写时，最好在每段之前根据内容标出小标题，或以明确的观点加以概括，使标题或观点与内容浑然一体。 最后，是先进事迹材料的署名。一般说，整理先进个人和先进集体的材料，都是以本级组织或上级组织的名义；是代表组织意见的。因此，材料整理完后，应经有关领导同志审定，以相应一级组织正式署名上报。这类材料不宜以个人名义署名。 写作典型经验材料-般包括以下几部分： (1)标题。有多种写法，通常是把典型经验高度集中地概括出来，一
How to manage time Time treats everyone fairly that we all have 24 hours per day. Some of us are capable to make good use of time while some find it hard to do so. Knowing how to manage them is essential in our life. Take myself as an example. When I was still a senior high student, I was fully occupied with my studies. Therefore, I hardly had spare time to have fun or develop my hobbies. But things were changed after I entered university. I got more free time than ever before. But ironically, I found it difficult to adjust this kind of brand-new school life and there was no such thing called time management on my mind. It was not until the second year that I realized I had wasted my whole year doing nothing. I could have taken up a Spanish course. I could have read ten books about the stories of successful people. I could have applied for a part-time job to earn some working experiences. B ut I didn’t spend my time on any of them. I felt guilty whenever I looked back to the moments that I just sat around doing nothing. It’s said that better late than never. At least I had the consciousness that I should stop wasting my time. Making up my mind is the first step for me to learn to manage my time. Next, I wrote a timetable, setting some targets that I had to finish each day. For instance, on Monday, I must read two pieces of news and review all the lessons that I have learnt on that day. By the way, the daily plan that I made was flexible. If there’s something unexpected that I had to finish first, I would reduce the time for resting or delay my target to the next day. Also, I would try to achieve those targets ahead of time that I planed so that I could reserve some more time to relax or do something out of my plan. At the beginning, it’s kind of difficult to s tick to the plan. But as time went by, having a plan for time in advance became a part of my life. At the same time, I gradually became a well-organized person. Now I’ve grasped the time management skill and I’m able to use my time efficiently.
英语演讲稿：未来的工作 这篇《英语演讲稿范文：未来的工作》，是特地，希望对大家有所帮助！ 热门演讲推荐：竞聘演讲稿 | 国旗下演讲稿 | 英语演讲稿 | 师德师风演讲稿 | 年会主持词 | 领导致辞 everybody good afternoon:. first of all thank the teacher gave me a story in my own future ideal job. everyone has a dream job. my dream is to bee a boss, own a pany. in order to achieve my dreams, i need to find a good job, to accumulate some experience and wealth, it is the necessary things of course, in the school good achievement and rich knowledge is also very important. good achievement and rich experience can let me work to make the right choice, have more opportunities and achievements. at the same time, munication is very important, because it determines whether my pany has a good future development. so i need to exercise their municative ability. i need to use all of the free time to learn
小学生个人读书事迹简介怎么写800字 书,是人类进步的阶梯,苏联作家高尔基的一句话道出了书的重要。书可谓是众多名人的“宠儿”。历来,名人说出关于书的名言数不胜数。今天小编在这给大家整理了小学生个人读书事迹,接下来随着小编一起来看看吧! 小学生个人读书事迹1 “万般皆下品,惟有读书高”、“书中自有颜如玉,书中自有黄金屋”,古往今来,读书的好处为人们所重视,有人“学而优则仕”,有人“满腹经纶”走上“传道授业解惑也”的道路……但是,从长远的角度看,笔者认为读书的好处在于增加了我们做事的成功率,改善了生活的质量。 三国时期的大将吕蒙,行伍出身,不重视文化的学习,行文时,常常要他人捉刀。经过主君孙权的劝导,吕蒙懂得了读书的重要性,从此手不释卷,成为了一代儒将,连东吴的智囊鲁肃都对他“刮目相待”。后来的事实证明,荆州之战的胜利,擒获“武圣”关羽,离不开吕蒙的“运筹帷幄,决胜千里”,而他的韬略离不开平时的读书。由此可见,一个人行事的成功率高低,与他的对读书,对知识的重视程度是密切相关的。 的物理学家牛顿曾近说过,“如果我比别人看得更远,那是因为我站在巨人的肩上”,鲜花和掌声面前,一代伟人没有迷失方向,自始至终对读书保持着热枕。牛顿的话语告诉我们,渊博的知识能让我们站在更高、更理性的角度来看问题,从而少犯错误,少走弯路。
读书的好处是显而易见的,但是,在社会发展日新月异的今天,依然不乏对读书,对知识缺乏认知的人,《今日说法》中我们反复看到农民工没有和用人单位签订劳动合同,最终讨薪无果;屠户不知道往牛肉里掺“巴西疯牛肉”是犯法的;某父母坚持“棍棒底下出孝子”,结果伤害了孩子的身心,也将自己送进了班房……对书本,对知识的零解读让他们付出了惨痛的代价,当他们奔波在讨薪的路上,当他们面对高墙电网时,幸福,从何谈起?高质量的生活,从何谈起? 读书,让我们体会到“锄禾日当午,汗滴禾下土”的艰辛;读书,让我们感知到“四海无闲田,农夫犹饿死”的无奈;读书,让我们感悟到“为报倾城随太守,西北望射天狼”的豪情壮志。 读书的好处在于提高了生活的质量,它填补了我们人生中的空白,让我们不至于在大好的年华里无所事事,从书本中,我们学会提炼出有用的信息,汲取成长所需的营养。所以,我们要认真读书,充分认识到读书对改善生活的重要意义,只有这样,才是一种负责任的生活态度。 小学生个人读书事迹2 所谓读一本好书就是交一个良师益友,但我认为读一本好书就是一次大冒险,大探究。一次体会书的过程,真的很有意思,咯咯的笑声,总是从书香里散发;沉思的目光也总是从书本里透露。是书给了我启示,是书填补了我无聊的夜空,也是书带我遨游整个古今中外。所以人活着就不能没有书,只要爱书你就是一个爱生活的人,只要爱书你就是一个大写的人,只要爱书你就是一个懂得珍惜与否的人。可真所谓
关于坚持的英语演讲稿 Results are not important, but they can persist for many years as a commemoration of. Many years ago, as a result of habits and overeating formed one of obesity, as well as indicators of overall physical disorders, so that affects my work and life. In friends to encourage and supervise, the participated in the team Now considered to have been more than three years, neither the fine rain, regardless of winter heat, a day out with 5:00 time. The beginning, have been discouraged, suffering, and disappointment, but in the end of the urging of friends, to re-get up, stand on the playground. 成绩并不重要，但可以作为坚持多年晨跑的一个纪念。多年前，由于庸懒习惯和暴饮暴食，形成了一身的肥胖，以及体检指标的全盘失常，以致于影响到了我的工作和生活。在好友的鼓励和督促下，参加了晨跑队伍。现在算来，已经三年多了，无论天晴下雨，不管寒冬酷暑，每天五点准时起来出门晨跑。开始时，也曾气馁过、痛苦过、失望过，但最后都在好友们的催促下，重新爬起来，站到了操场上。 In fact, I did not build big, nor strong muscles, not a sport-born people. Over the past few years to adhere to it, because I have a team behind, the strength of a strongteam here, very grateful to our team, for a long time, we encourage each other, and with sweat, enjoying common health happy. For example, Friends of the several run in order to maintain order and unable to attend the 10，000 meters race, and they are always concerned about the brothers and promptly inform the place and time, gives us confidence and courage. At the same time, also came on their own inner desire and pursuit for a good health, who wrote many of their own log in order to refuel for their own, and inspiring. 其实我没有高大身材，也没健壮肌肉，天生不属于运动型的人。几年来能够坚持下来，因为我的背后有一个团队，有着强大团队的力量，在这里，非常感谢我们的晨跑队，长期以来，我们相互鼓励着，一起流汗，共同享受着健康带来的快
1.How to build a business that lasts100years 0:11Imagine that you are a product designer.And you've designed a product,a new type of product,called the human immune system.You're pitching this product to a skeptical,strictly no-nonsense manager.Let's call him Bob.I think we all know at least one Bob,right?How would that go? 0:34Bob,I've got this incredible idea for a completely new type of personal health product.It's called the human immune system.I can see from your face that you're having some problems with this.Don't worry.I know it's very complicated.I don't want to take you through the gory details,I just want to tell you about some of the amazing features of this product.First of all,it cleverly uses redundancy by having millions of copies of each component--leukocytes,white blood cells--before they're actually needed,to create a massive buffer against the unexpected.And it cleverly leverages diversity by having not just leukocytes but B cells,T cells,natural killer cells,antibodies.The components don't really matter.The point is that together,this diversity of different approaches can cope with more or less anything that evolution has been able to throw up.And the design is completely modular.You have the surface barrier of the human skin,you have the very rapidly reacting innate immune system and then you have the highly targeted adaptive immune system.The point is,that if one system fails,another can take over,creating a virtually foolproof system. 1:54I can see I'm losing you,Bob,but stay with me,because here is the really killer feature.The product is completely adaptive.It's able to actually develop targeted antibodies to threats that it's never even met before.It actually also does this with incredible prudence,detecting and reacting to every tiny threat,and furthermore, remembering every previous threat,in case they are ever encountered again.What I'm pitching you today is actually not a stand-alone product.The product is embedded in the larger system of the human body,and it works in complete harmony with that system,to create this unprecedented level of biological protection.So Bob,just tell me honestly,what do you think of my product? 2:47And Bob may say something like,I sincerely appreciate the effort and passion that have gone into your presentation,blah blah blah-- 2:56(Laughter) 2:58But honestly,it's total nonsense.You seem to be saying that the key selling points of your product are that it is inefficient and complex.Didn't they teach you 80-20?And furthermore,you're saying that this product is siloed.It overreacts, makes things up as it goes along and is actually designed for somebody else's benefit. I'm sorry to break it to you,but I don't think this one is a winner.
关于工作的优秀英语演讲稿 Different people have various ambitions. Some want to be engineers or doctors in the future. Some want to be scientists or businessmen. Still some wish to be teachers or lawers when they grow up in the days to come. Unlike other people, I prefer to be a farmer. However, it is not easy to be a farmer for Iwill be looked upon by others. Anyway,what I am trying to do is to make great contributions to agriculture. It is well known that farming is the basic of the country. Above all, farming is not only a challenge but also a good opportunity for the young. We can also make a big profit by growing vegetables and food in a scientific way. Besides we can apply what we have learned in school to farming. Thus our countryside will become more and more properous. I believe that any man with knowledge can do whatever they can so long as this job can meet his or her interest. All the working position can provide him with a good chance to become a talent. 1 ————来源网络整理，仅供供参考
个人先进事迹简介 01 在思想政治方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.利用课余时间和党课机会认真学习政治理论,积极向党组织靠拢. 在学习上,xxxx同学认为只有把学习成绩确实提高才能为将来的实践打下扎实的基础,成为社会有用人才.学习努力、成绩优良. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意识和良好的心理素质和从容、坦诚、乐观、快乐的生活态度,乐于帮助身边的同学,受到师生的好评. 02 xxx同学认真学习政治理论,积极上进,在校期间获得原院级三好生,和校级三好生,优秀团员称号,并获得三等奖学金. 在学习上遇到不理解的地方也常常向老师请教,还勇于向老师提出质疑.在完成自己学业的同时,能主动帮助其他同学解决学习上的难题,和其他同学共同探讨,共同进步. 在社会实践方面,xxxx同学参与了中国儿童文学精品“悦”读书系,插画绘制工作,xxxx同学在班中担任宣传委员,工作积极主动,认真负责,有较强的组织能力.能够在老师、班主任的指导下独立完成学院、班级布置的各项工作. 03 xxx同学在政治思想方面积极进取,严格要求自己.在学习方面刻苦努力,不断钻研,学习成绩优异,连续两年荣获国家励志奖学金；作
为一名学生干部,她总是充满激情的迎接并完成各项工作,荣获优秀团干部称号.在社会实践和志愿者活动中起到模范带头作用. 04 xxxx同学在思想方面,积极要求进步,为人诚实,尊敬师长.严格 要求自己.在大一期间就积极参加了党课初、高级班的学习,拥护中国共产党的领导,并积极向党组织靠拢. 在工作上,作为班中的学习委员,对待工作兢兢业业、尽职尽责 的完成班集体的各项工作任务.并在班级和系里能够起骨干带头作用.热心为同学服务,工作责任心强. 在学习上,学习目的明确、态度端正、刻苦努力,连续两学年在 班级的综合测评排名中获得第1.并荣获院级二等奖学金、三好生、优秀班干部、优秀团员等奖项. 在社会实践方面,积极参加学校和班级组织的各项政治活动,并 在志愿者活动中起到模范带头作用.积极锻炼身体.能够处理好学习与工作的关系,乐于助人,团结班中每一位同学,谦虚好学,受到师生的好评. 05 在思想方面,xxxx同学积极向上,热爱祖国、热爱中国共产党,拥护中国共产党的领导.作为一名共产党员时刻起到积极的带头作用,利用课余时间和党课机会认真学习政治理论. 在工作上,作为班中的团支部书记,xxxx同学积极策划组织各类 团活动,具有良好的组织能力. 在学习上,xxxx同学学习努力、成绩优良、并热心帮助在学习上有困难的同学,连续两年获得二等奖学金. 在生活中,善于与人沟通,乐观向上,乐于助人.有健全的人格意 识和良好的心理素质.
尊敬的领导，老师，亲爱的同学们， 大家好！我是5班的梁浩东。今天早上我坐车来学校的路上，我仔细观察了路上形形色色的人，有开着小车衣着精致的叔叔阿姨，有市场带着倦容的卖各种早点的阿姨，还有偶尔穿梭于人群中衣衫褴褛的乞丐。于是我问自己，十几年后我会成为怎样的自己，想成为社会成功人士还是碌碌无为的人呢，答案肯定是前者。那么十几年后我怎样才能如愿以偿呢，成为一个受人尊重，有价值的人呢？正如我今天演讲的题目是：自主管理。 大家都知道爱玩是我们孩子的天性，学习也是我们的责任和义务。要怎样处理好这些矛盾，提高自主管理呢？ 首先，我们要有小主人翁思想，自己做自己的主人，要认识到我们学习，生活这一切都是我们自己走自己的人生路，并不是为了报答父母，更不是为了敷衍老师。 我认为自主管理又可以理解为自我管理，在学习和生活中无处不在，比如通过老师，小组长来管理约束行为和同学们对自身行为的管理都属于自我管理。比如我们到一个旅游景点，看到一块大石头，有的同学特别兴奋，会想在上面刻上：某某某到此一游话。这时你就需要自我管理，你需要提醒自己，这样做会破坏景点，而且是一种素质低下的表现。你设想一下，如果别人家小孩去你家墙上乱涂乱画，你是何种感受。同样我们把自主管理放到学习上，在我们想偷懒，想逃避，想放弃的时候，我们可以通过自主管理来避免这些，通过他人或者自己的力量来完成。例如我会制定作息时间计划表，里面包括学习，运动，玩耍等内容的完成时间。那些学校学习尖子，他们学习好是智商高于我们吗，其实不然，在我所了解的哪些优秀的学霸传授经验里，就提到要能够自我管理，规范好学习时间的分分秒秒，只有辛勤的付出，才能取得优异成绩。 在现实生活中，无数成功人士告诉我们自主管理的重要性。十几年后我想成为一位优秀的，为国家多做贡献的人。亲爱的同学们，你们们？让我们从现在开始重视和执行自主管理，十几年后成为那个你想成为的人。 谢谢大家！
关于工作的英语演讲稿 【篇一：关于工作的英语演讲稿】 关于工作的英语演讲稿 different people have various ambitions. some want to be engineers or doctors in the future. some want to be scientists or businessmen. still some wish to be teachers or lawers when they grow up in the days to come. unlike other people, i prefer to be a farmer. however, it is not easy to be a farmer for iwill be looked upon by others. anyway,what i am trying to do is to make great contributions to agriculture. it is well known that farming is the basic of the country. above all, farming is not only a challenge but also a good opportunity for the young. we can also make a big profit by growing vegetables and food in a scientific way. besides we can apply what we have learned in school to farming. thus our countryside will become more and more properous. i believe that any man with knowledge can do whatever they can so long as this job can meet his or her interest. all the working position can provide him with a good chance to become a talent. 【篇二：关于责任感的英语演讲稿】 im grateful that ive been given this opportunity to stand here as a spokesman. facing all of you on the stage, i have the exciting feeling of participating in this speech competition. the topic today is what we cannot afford to lose. if you ask me this question, i must tell you that i think the answer is a word---- responsibility. in my elementary years, there was a little girl in the class who worked very hard, however she could never do satisfactorily in her lessons. the teacher asked me to help her, and it was obvious that she expected a lot from me. but as a young boy, i was so restless and thoughtless, i always tried to get more time to play and enjoy myself. so she was always slighted over by me. one day before the final exam, she came up to me and said, could you please explain this to me? i can not understand it. i
Dear teacher and colleagues: my topic is on “spare time”. It is a huge blessing that we can work 996. Jack Ma said at an Ali's internal communication activity, That means we should work at 9am to 9pm, 6 days a week .I question the entire premise of this piece. but I'm always interested in hearing what successful and especially rich people come up with time .So I finally found out Jack Ma also had said :”i f you don’t put out more time and energy than others ,how can you achieve the success you want? If you do not do 996 when you are young ,when will you ?”I quite agree with the idea that young people should fight for success .But there are a lot of survival activities to do in a day ,I want to focus on how much time they take from us and what can we do with the rest of the time. As all we known ,There are 168 hours in a week .We sleep roughly seven-and-a-half and eight hours a day .so around 56 hours a week . maybe it is slightly different for someone . We do our personal things like eating and bathing and maybe looking after kids -about three hours a day .so around 21 hours a week .And if you are working a full time job ,so 40 hours a week , Oh! Maybe it is impossible for us at
关于人英语演讲稿(精选多篇) 关于人的优美句子 1、“黑皮小子”是我对在公交车上偶遇两次的一个男孩的称呼代号。一听这个外号，你也定会知道他极黑了。他的脸总是黑黑的；裸露在短袖外的胳膊也是黑黑的；就连两只有厚厚耳垂的耳朵也那么黑黑的，时不时像黑色的猎犬竖起来倾听着什么；黑黑的扁鼻子时不时地深呼吸着，像是在警觉地嗅着什么异样的味道。 2、我不知道，如何诠释我的母亲，因为母亲淡淡的生活中却常常跳动着不一样的间最无私、最伟大、最崇高的爱，莫过于母爱。无私，因为她的爱只有付出，无需回报；伟大，因为她的爱寓于
普通、平凡和简单之中；崇高，是因为她的爱是用生命化作乳汁，哺育着我，使我的生命得以延续，得以蓬勃，得以灿烂。 3、我的左撇子伙伴是用左手写字的，就像我们的右手一样挥洒自如。在日常生活中，曾见过用左手拿筷子的，也有像超级林丹用左手打羽毛球的，但很少碰见用左手写字的。中国汉字笔画笔顺是左起右收，适合用右手写字。但我的左撇子伙伴写字是右起左收的，像鸡爪一样迈出田字格，左看右看，上看下看，每一个字都很难看。平时考试时间终了，他总是做不完试卷。于是老师就跟家长商量，决定让他左改右写。经过老师引导，家长配合，他自己刻苦练字，考试能够提前完成了。现在他的字像他本人一样阳光、帅气。 4、老师，他们是辛勤的园丁，帮助着那些幼苗茁壮成长。他们不怕辛苦地给我们改厚厚一叠的作业，给我们上课。一步一步一点一点地给我们知识。虽然
他们有时也会批评一些人，但是他们的批评是对我们有帮助的，我们也要理解他们。那些学习差的同学，老师会逐一地耐心教导，使他们的学习突飞猛进。使他们的耐心教导培养出了一批批优秀的人才。他们不怕辛苦、不怕劳累地教育着我们这些幼苗，难道不是美吗？ 5、我有一个表妹，还不到十岁，她那圆圆的小脸蛋儿，粉白中透着粉红，她的头发很浓密，而且好像马鬓毛一样的粗硬，但还是保留着孩子一样的蓬乱的美，卷曲的环绕着她那小小的耳朵。说起她，她可是一个古灵精怪的小女孩。 6、黑皮小子是一个善良的人，他要跟所有见过的人成为最好的朋友！这样人人都是他的好朋友，那么人人都是好友一样坦诚、关爱相交，这样人与人自然会和谐起来，少了许多争执了。 7、有人说，老师是土壤，把知识化作养分，传授给祖国的花朵，让他们茁壮成长。亦有人说，老师是一座知识的桥梁，把我们带进奇妙的科学世界，让
优秀党务工作者事迹简介范文 优秀党务工作者事迹简介范文 ***，男，198*年**月出生，200*年加入党组织，现为***支部书记。从事党务工作以来，兢兢业业、恪尽职守、辛勤工作，出色地完成了各项任务，在思想上、政治上同党中央保持高度一致，在业务上不断进取，团结同事，在工作岗位上取得了一定成绩。 一、严于律己，勤于学习 作为一名党务工作者，平时十分注重知识的更新，不断加强党的理论知识的学习，坚持把学习摆在重要位置，学习领会和及时掌握党和国家的路线、方针、政策，特别是党的十九大精神，注重政治理论水平的提高，具有坚定的理论信念;坚持党的基本路线，坚决执行党的各项方针政策，自觉履行党员义务，正确行使党员权利。平时注重加强业务和管理知识的学习，并运用到工作中去，不断提升自身工作能力，具有开拓创新精神，在思想上、政治上和行动上时刻同党中央保持高度一致。 二、求真务实，开拓进取 在工作中任劳任怨，踏实肯干，坚持原则，认真做好学院的党务工作，按照党章的要求，严格发展党员的每一个步骤，认真细致的对待每一份材料。配合党总支书记做好学院的党建工作，完善党总支建设方面的文件、材料和工作制度、管理制度等。
三、生活朴素，乐于助人 平时重视与同事间的关系，主动与同事打成一片，善于发现他人的难处，及时妥善地给予帮助。在其它同志遇到困难时，积极主动伸出援助之手，尽自己最大努力帮助有需要的人。养成了批评与自我批评的优良作风，时常反省自己的工作，学习和生活。不但能够真诚的指出同事的缺点，也能够正确的对待他人的批评和意见。面对误解，总是一笑而过，不会因为误解和批评而耿耿于怀，而是诚恳的接受，从而不断的提高自己。在生活上勤俭节朴，不铺张浪费。 身为一名老党员，我感到责任重大，应该做出表率，挤出更多的时间来投入到**党总支的工作中，不找借口，不讲条件，不畏困难，将总支建设摆在更重要的位置，解开工作中的思想疙瘩，为攻坚克难铺平道路，以支部为纽带，像战友一样团结，像家庭一样维系，像亲人一样关怀，践行入党誓言。把握机遇，迎接挑战，不负初心。
关于时间的英语演讲稿范文_演讲稿 and organizing people to learn from advanced areas to broaden their horizons in order to understand the team of cadres working conditions in schools, the ministry of education has traveled a number of primary and secondary schools to conduct research, listen to the views of the school party and government leaders to make school leadership cadres receive attention and guidance of the ministry of education to carry out a variety of practical activities to actively lead the majority of young teachers work hard to become qualified personnel and for them to put up the cast talent stage, a single sail swaying, after numerous twists and turns arrived in port, if there is wind, a hand, and naturally smooth arrival and guide students to strive to e xcel, need to nazhen “wind” - teacher. teachers should be ideological and moral education, culture education and the needs of students organically combining various activities for the students or students to carry out their own. for example: school quiz competitions, essay contests, ke benju performances and other activities to enable students to give full play to their talents. teachers rush toil, in order to that will enable students to continue to draw nutrients, to help them grow up healthily and become pillars of the country before. for all students in general education, the government departments have also not forget those who cared about the