The isolation and characterization of the gene(s) associated with and potentially responsible for the regulation of apomixis (asexual) and sexual reproduction in the grass species Tripsacum dactyloides is quintessential to agricultural advancement. Apomixis is the mechanism by which plants can produce seed without fertilization, where all progeny are genetically identical to the maternal parent. In natural populations of the genus Tripsacum, lower ploidy forms (i.e., diploid, 2n=36) reproduce sexually and the higher ploidy forms (triploid, 3n=54; tetraploid, 4n=72; etc.) reproduce asexually via apomixis. In order to gain a better understanding of sexual reproductive processes in plants, subtractive hybridization was performed on early and late female inflorescence gene products. This procedure allows for the recovery of gene products in the form of complimentary DNA, cDNA molecules, which correspond to messenger RNA (mRNA) present. These cDNA molecules were then used to extract unique sequence messages from the early developmental stage ovule tissue of diploid T. dactyloides. These cDNA molecules will allow for the direct isolation of the original form of the gene(s) from a large fragment library of the Tripsacum genome. Isolation and characterization of these gene(s) is of pivotal importance to our understanding of alternate modes of reproduction in Tripsacum. / Department of Biology

Thesis (M.S.)--University of Wisconsin--Madison, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 114-129).

Thesis (Ph. D.)--Ohio State University, 2007. / Full text release at OhioLINK's ETD Center delayed at author's request

O presente estudo teve como objetivo principal avaliar o potencial da madeira de dois clones do híbrido Eucalyptus grandis x Eucalyptus urophylla para a produção de lâminas e manufatura de painéis compensados. Foram coletadas 5 árvores para cada clone (I e II) e duas toras de cada árvore, sendo uma da base (A) e outra subseqüente (B), totalizando 20 toras. As toras após descascamento e aquecimento em água quente foram processadas em torno laminador gerando lâminas de 2,00 mm de espessura nominal. O rendimento médio do processo de laminação foi de 51,74% para as toras do clone I e de 56,81% para as toras do clone II. A qualidade das lâminas produzidas foi avaliada com base na Norma de Controle de Qualidade e Classificação de Compensados, da ABNT. O clone I gerou lâminas de melhor qualidade: 11,94 % na classe A; 32,84 % na B; 54,48 % na C e 0,75 % na classe D, enquanto que o clone II gerou: 1,20 % na classe A; 8,40 % na B; 67,47 % na C e 22,89 % na classe D. Foram manufaturados compensados de 5 camadas, com lâminas da classe C para as capas e o miolo, coladas com adesivo à base de uréia-formaldeído. Os fatores de tratamento empregados na manufatura foram: clone (I e II), gramatura de cola (320 e 360 g/m2) e tempo de prensagem (8 e 12 minutos). O delineamento experimental foi inteiramente casualizado com arranjo fatorial do tipo 2 x 2 x 2. A partir dos compensados manufaturados foram obtidos corpos de prova para avaliação das propriedades físicas – massa específica aparente, absorção superficial de água, absorção total de água, inchamento mais recuperação em espessura e recuperação em espessura, e avaliação das propriedades mecânicas – flexão estática paralela e perpendicular (MOR e MOE) e resistência da linha de colagem ao esforço do cisalhamento nas condições seca e úmida. A análise estatística dos resultados das propriedades físicas e mecânicas foi realizada através de uma análise de variância. Não houve interação significativa entre os fatores clone, gramatura de cola e tempo de prensagem, considerando todas as variáveis avaliadas. Foram detectadas diferenças significativas para o fator clone em relação às variáveis massa específica aparente (maior para o clone I), absorção superficial e total de água (menores para o clone I); resistência da linha de colagem ao esforço do cisalhamento – condição seca e flexão estática – MOR paralelo e perpendicular (maiores para o clone I). Para o fator gramatura de cola não houve diferença significativa entre os tratamentos para nenhuma das variáveis avaliadas. Houve diferença significativa para o fator tempo de prensagem em relação às variáveis absorção superficial de água (menor para o tempo de prensagem de 12 minutos), inchamento mais recuperação em espessura e recuperação em espessura (menores para o tempo de prensagem de 8 minutos). A conclusão do trabalho é que as madeiras de ambos clones do híbrido Eucalyptus grandis x Eucalyptus urophylla apresentam alto potencial para produção de lâminas e manufatura de compensados. / The main objective of this work was to evaluate the potencial of eucalyptus grandis x Eucalyptus urophylla hybrid clones wood for plywood and veneer production. Five (5) trees were collected for each clone (I and II) and 2 logs of each tree, being one from base (A) and other subsequent one (B), totaling 20 logs. The logs after debarked and heated in hot water were processed in rotary cutting lathe generating veneers of 2,00 mm nominal thickness. The peeling yield was evaluated and mean values were 51,74% from clone I logs and 56,81% from the II one. The veneer quality graded was conduced following Norma de Controle de Qualidade e Classificação de Compensados, Brazilians standards. The clone I generated veneers of better quality: 11,94% of grade A veneer; 32,84% of B; 54,48% of C and 0,75% of grade D veneer, while the clone II generated: 1,20% of grade A veneer; 8,40% of B; 67,47% of C and 22,89% of grade D veneer. 5 layers plywood was manufactured with grade C veneers. The plywood manufacture treatment factors were: clone (I and II), glue amount (320 and 360 g/m2) and press time (8 and 12 minutes). From manufacture plywood were obtained specimens to evaluate the physical properties - apparent specific mass, superficial absorption of water, total absorption of water, thickness swelling more thickness recovery and thickness recovery, and the mechanical properties - parallel and perpendicular static bending (MOR and MOE) and bonding line shear test in the dry and wet conditions. The result obtained during the physical and mechanical assessments of plywood were analyzed using a variance analysis, executed by SAS (Statistical Analysis System). There was not significant interaction among the factors clone, glue amount and press time, considering all the appraised variables. Significant differences were detected for factor clone in relation to the variables apparent specific mass (clone I higher than clone II), superficial and total absorption of water (clone I smaller than clone II); bonding line shear test (dry condition) and static bending - parallel and perpendicular MOR (clone I higher than clone II). To the factor glue amount there was not significant difference among the treatments for none of the appraised variables. There was significant difference for the factor press time in relation to the variables superficial absorption of water (12 minutes smaller than 8 minutes), thickness swelling more thickness recovery and thickness recovery (8 minutes smaller than 12 minutes). It's concluded that Eucalyptus grandis x Eucalyptus urophylla hybrid clones wood have a high potencial for phywood and veneer production.

Backcross populations (BC) from Medicago sativa L. x M. dzhawakhetica Bordz. hybrids were analyzed for chromosome number, fertility and morphological characteristics. Previously obtained F1 hybrids were recovered when diploid (2n = 2x = 16) M. sativa was crossed with tetraploid (2n = 4x = 32) M. dzhawakhetica. Resulting F1 hybrids were triploid (2n = 3x = 24), completely male sterile and had low levels of female fertility. Subsequent populations were obtained by successive backcrossing to unrelated (4x) M. sativa clones. The BC1 plants were pentaploid (2n = 5x = 40) and both male and female fertile. BC2 populations had chromosome numbers ranging from 2n = 32 to 48, and most plants (94% were male and female fertile. BC3 populations were tetraploid (2n = 32) or near tetraploid (2n = 33) and were morphologically similar to M. sativa. Preliminary analysis of mitochondrial nucleic acids by agarose gel electrophoresis, indicated biparental inheritance of this organelle in the F1 hybrids; however, further analysis provided inconclusive results.

Thesis (MSc)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: The goals of this project were firstly to develop the tissue preparation and in situ hybridisation protocols for sugarcane culm tissue, and secondly to use the developed techniques to examine the expression patterns of three invertase isoforms in sugarcane internodes of various developmental stages. Sugarcane invertases have been the focus of intense research for many years, yet almost nothing is known of their tissue-specific distribution. It was thought that by characterising their expression patterns using in situ hybridisation, more knowledge of their functions and involvement in sucrose accumulation would be gained. Although in situ hybridisation is now regularly used to study gene expression in plants, there is to date only a single publication describing its use on immature sugarcane tissue. Therefore this technique needed further development, and this was achieved by comparing different tissue preparation methods, as well as by systematically testing the various parameters pertaining to each method. The in situ hybridization technique was also developed by testing and comparing a number of key parameters. It was found that fixing whole mount tissue for 48 h preserved sugarcane tissue adequately. High hybridization temperatures and probe concentrations provided the best signal, and including pre-treatment with HCl and Pronase was essential in sensitizing the tissue to the probe. A less viscous detection buffer reduced both osmotic effects and time required for signal detection. In the second part of this study, the developed method was used to examine the expression patterns of the three invertase isoforms in young, maturing and mature internodes of sugarcane, and the results were complemented with Northern blot analysis. Transcript of all three isoforms was found to be present in the storage parenchyma and in the phloem tissue. Transcript levels of all three isoforms declined in maturing tissue, with soluble acid invertase declining sharply and dropping below detection in maturing and mature tissue. Transcript levels of cell wall invertase and neutral invertase declined only gradually, and appreciable levels of both were still present in mature tissue. Acid invertase is suggested to be mainly involved in internode elongation, while cell wall invertase would appear to play important roles in phloem unloading and turgor control. Neutral invertase is suggested to be involved in either sucrose cycling or maintenance of hexose pools, however the function of this enzyme remains unclear. This study has demonstrated the value of in situ hybridization, yet at the same time has shown its limitations, especially when more traditional biochemical techniques are not employed to complement the results. Although the precise functions of the invertase isoforms in sugarcane remain inconclusive, this study has opened up the way for tissuespecific promoter design and future in situ studies of sugarcane invertases / AFRIKAANSE OPSOMMING: Die doel van hierdie projek was tweeledig: eerstens om weefselvoorbereiding en in situhibridisasie- protokolle vir die stingelweefsel van suikerriet te ontwikkel; en tweedens om die ontwikkelde tegnieke te gebruik om die uitdrukkingspatrone van drie invertaseisovorme in die suikerriet-internodes van verskeie ontwikkelingstadia te ondersoek. Suikerriet-invertases is al vir jare lank die fokus van intense navorsing, maar baie min is bekend oor hulle weefselspesifieke verspreiding. Die idee was om meer kennis oor suikerriet-invertases se funksies en betrokkenheid by sukrose-akkumulasie te verkry deur in situ-hibridisasie te gebruik om hulle uitdrukkingspatrone te karakteriseer. Alhoewel in situ-hibridisasie deesdae gereeld gebruik word om geenuitdrukking in plante te bestudeer, is daar tot op datum slegs een publikasie wat die gebruik daarvan in onvolwasse suikerrietweefsel beskryf. Hierdie tegniek moes dus verder ontwikkel word, en dit is gedoen deur verskillende weefselvoorbereidingsmetodes te vergelyk en sistematies die verskillende parameters wat op elke metode van toepassing is te toets. Die in situ-hibridisasie-tegniek is ook ontwikkel deur die toetsing en vergelyking van 'n aantal sleutelparameters. Daar is gevind dat suikerrietweefsel voldoende gepreserveer word deur die intakte gemonteerde weefsel vir 48 uur te fikseer. Hoë hibridisasietemperature en hoë peilerkonsentrasies het die beste sein gegee; die insluiting van voorbehandeling met HCl en Pronase was noodsaaklik om die weefsel meer gevoelig vir die peiler te maak. Osmotiese invloede en die tyd nodig vir seindeteksie is verminder deur die viskositeit van die buffer te verminder. In die tweede deel van die studie is die ontwikkelde metode gebruik om die uitdrukkingspatrone van die drie invertase-isovorme in jong, ontwikkelende en volwasse internodes te ondersoek en die resultate is deur 'n noordelike oordraganalise gekomplementeer. Transkripte van al drie isovorme is in die stoorparenchiem en floëemweefsel gevind. Transkripvlakke van al drie isovorme het afgeneem in ontwikkelende weefsel, met oplosbare suurinvertase wat skerp afgeneem en tot onder die deteksie-limiet gedaal het in ontwikkelende en volwasse weefsel. Transkripvlakke van selwandinvertase en neutrale invertase het slegs geleidelik afgeneem en merkbare vlakke van albei was teenwoording in ontwikkelende en volwasse weefsel. Daar word voorgestel dat suurinvertase hoofsaaklik betrokke is by internodeverlenging, terwyl selwandinvertase skynbaar 'n belangrike rol in floëem-ontlading en turgor-beheer speel. Daar word voorgestel dat neutrale invertase betrokke is óf by die sukrose-sirkulering óf by die onderhoud van heksose-poele; die funksie van hierdie ensiem is egter steeds nie duidelik nie. Hierdie studie het die waarde van in situ-hibridisasie gedemonstreer maar terselfdetyd ook die beperkinge daarvan uitgewys, veral as meer tradisionele biochemiese tegnieke nie gebruik word om die resultate aan te vul nie. Alhoewel daar onsekerheid is oor die presiese funksies van die invertase-isovorme in suikerriet, het die studie die weg gebaan vir weefselspesifieke promotorontwerp en toekomstige in situ-studies van suikerrietinvertases.

Orientador: Maria do Carmo Estanislau do Amaral / Dissertação (mestrado) - Universidade EStadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-20T01:02:29Z (GMT). No. of bitstreams: 1 Trad_RafaelaJorge_M.pdf: 22525547 bytes, checksum: ab1b354e662d2efdfd89ddde29c10f86 (MD5) Previous issue date: 2012 / Resumo: O cerrado, uma formacao vegetal tipica do Brasil central, e um dos biomas com maior biodiversidade de especies, sendo classificado como um "hotspot". Atualmente, a acao antropogenica no cerrado tem causado muito desmatamento, ameacando a existencia de muitas especies. Kielmeyera Mart. & Zucc. (Clusiaceae s.l./Calophyllaceae) e um genero com aproximadamente 50 especies, das quais varias ocorrem no cerrado. Morfologicamente o genero e caracterizado por apresentar flores vistosas com corola contorta e numerosos estames, ovario trilocular e capsulas lenhosas com numerosas sementes aladas. Um dos elementos mais conspicuos do cerrado e Kielmeyera coriacea Mart. & Zucc., uma especie altamente variavel morfologicamente. A especie apresenta a maior amplitude ecologica para o genero e sua distribuicao geografica coincide, em maior parte, com a distribuicao do cerrado. K. coriacea e facilmente reconhecida por apresentar suber espesso, folhas verdes caducas e aglomeradas nos apices dos ramos, padrao de venacao caracteristico e flores alvas e odoriferas. Na ultima revisao realizada para o genero Kielmeyera (Saddi 1982), a circunscricao de K. coriacea foi alterada, mas permaneceu problematica. Visando organizar a variacao, o autor propoe o reconhecimento de duas subespecies e sete variedades, formando o que e conhecido atualmente como "complexo K. coriacea". Faz parte desse complexo tambem a especie K. grandiflora (Wawra) Saddi, considerada antes uma variedade de K. coriacea. Para estudar o complexo o presente trabalho utilizou abordagens taxonomicas convencionais, a anatomica e a genetica. Foram realizadas observacoes de material de herbario e cortes das regioes marginais e medianas de folhas adultas de cinco populacoes, sendo: duas de K. coriacea subsp. coriacea, duas de K. coriacea subsp. tomentosa e uma de K. grandiflora, constituidas por dois individuos cada populacao. Para estudos de genetica populacional foram utilizados 12 pares de primers previamente desenvolvidos a partir de uma biblioteca enriquecida de microssatelites. Os marcadores foram amplificados em 27 populacoes com 20-30 individuos cada. A anatomia estrutural apresentou dois padroes claramente distintos e a genetica populacional indicou grande semelhanca entre os taxons pertencentes ao complexo. Os resultados nao corroboram a proposta de Saddi para taxonomia da espécie / Abstract: The Cerrado, a savanna-like vegetation typical of Central-Brazil, is one of the most species rich biomes of the world. It was classified as a "Biodiversity Hotspot". It is suffering strong anthropogenic pressures of different sources, and quite a number of species is seriously threatened. Kielmeyera Mart. & Zucc. (Clusiaceae s.l./ Calophyllaceae) is a genus of nearly 50 spp., several of which occur in the cerrado. Morphologically, the genus is characterized by large flowers with a contorted corolla and numerous stamens, a 3- locular ovary, and septicidal woody capsules with numerous winged seeds. One of the most common elements of the cerrado is Kielmeyera coriacea Mart. & Zucc., a morphologically highly variable species. It shows the widest ecological amplitude within the genus and its geographical distribution largely coincides with the cerrado biome. This species can be easily recognized by the thick corky bark, green coriaceous caducous leaves crown-like condensed at the end the branches, a characteristic venation and odoriferous, white flowers. In the last revision of the genus Kielmeyera (Nagib Saddi, 1982), the circumscription of K. coriacea remained problematic. To cope with a high variability, Saddi proposed two subspecies and seven varieties. The species is taxonomically so problematic that it is usually referred to as the "K. coriacea complex", to which also belongs K. grandiflora (Wawra) Saddi, formerly included as a variety in K. coriacea. To help with the taxonomic study of this complex, the study was done with taxonomy work, population genetics and structural anatomy of the leaves. For anatomy, two populations from each subspecies of K. coriacea and one population of K. grandiflora, consisting of 2 plants, were sampled. For genetics studies twelve primers pairs were selected between the ones previously developed from an enriched library of K. coriacea . Two patterns were found according to the structural anatomy and taxonomy observations suggest that there are two or more species in the complex. According to genetics, the banding pattern varies from one to eight bands per individual. K. grandiflora showed a similar banding pattern. For our study we treated each subspecies of K. coriacea as one group and Kielmeyera grandiflora as a third. We sampled at least 5 populations for each group and 20-30 plants to represent each population. The results show how genetically similar individuals of K. coriacea are. They do not corroborate most of Saddi's ideas for a subdivision of the K. coriacea complex, but suggest that K. grandiflora and K. coriacea are distinct species (as proposed by Saddi) and that possibly the two subspecies of K. coriacea actually represent two distinct species / Mestrado / Biologia Vegetal / Mestre em Biologia Vegetal

O tomateiro (Solanum lycopersicum L.) é um interessante modelo para estudar a base genética da capacidade de formação de órgãos adventícios, uma vez que existem variações genéticas naturais consideráveis em seus parentes selvagens. Assim, sabese que o alelo dominante Rg1, presente no braço curto do cromossomo 3 de S. peruvianum, confere alta capacidade de regeneração de gemas caulinares. Usando uma coleção de 50 linhas de introgressão (ILs), cada uma contendo um pequeno segmento cromossômico de S. pennellii LA716 introgredido e mapeado na cultivar M82, foram realizados testes com explantes cotiledonares com 12 dias de idade cultivados em meio MS contendo 5,0 M BAP, e encontramos uma alta capacidade de regeneração de gemas caulinares nas IL3-2, IL6-1, IL7-1, IL 8-3, IL-9-1 e IL10-2. Isto significa que S. pennellii provavelmente possua alelos com capacidade superior para a regeneração in vitro nessas regiões cromossômicas, incluindo um possível novo alelo para Rg1 na IL3-2. Plântulas em F1 do cruzamento entre Micro-Tom x ILs e ILs x ILs provaram que a capacidade de regeneração de gemas caulinares foi dominante nas ILs 3-2, 6-1, 7-1 e 8-3, e que a capacidade de regeneração das IL8-3 aumentou a das outras ILs, comportando-se de uma maneira aditiva. Uma vez que as ILs 3-2, 7-1, 8-3 e 10-2 também aumentaram a formação de raízes em meio MS contendo 0,4 M ANA, elas podem apresentar novos alelos que controlam a fase de competência, estando aptas a assumir diferentes destinos celulares, ao invés da indução de um órgão específico. Também realizamos a introgressão dos alelos selecionados para o modelo genético Micro-Tom, o qual proporcionará a caracterização e isolamento de genes importantes para estudos de desenvolvimento de plantas e aplicações biotecnológicas. / Tomato (Solanum lycopersicum L.) is an attractive model to study the genetic basis of adventitious organ formation capacity, since there is considerable natural genetic variation in its wild relatives. Accordingly, it is known that the dominant Rg1 allele, present in the short arm of S. peruvianum chromosome 3, confers high shoot regeneration capacity. Using a set of 50 introgression lines (ILs), each containing small a chromosomal segment of S. pennellii LA716 introgressed and mapped into the tomato cultivar M82, we found a high shoot regeneration capacity for IL3-2, IL6-1, IL7-1, IL 8-3, IL-9-1 and IL10-2, when 12-days-old cotyledon explants were cultivated in MS medium containing 5.0 M BAP, suggesting that. S. pennellii might present superior alleles for in vitro regeneration in such chromosomal regions, including a possible novel allele for Rg1 in IL3-2. F1 seedlings from the crosses Micro-Tom x ILs and ILs x ILs demonstrated that the shoot regeneration capacity of the ILs 3-2, 6-1, 7-1 and 8-3 was dominant and that the regeneration ability of IL8-3 enhanced that of the other ILs in an additive manner. Since ILs 3-2, 7-1, 8-3, and 10-2 also exhibited enhanced root formation on MS medium containing 0.4 M NAA, these segments might contain novel alleles controlling the competence to assume distinct cell fates, rather than the induction of a specific organ. We also performed the introgression of such alleles into the genetic model system Micro-Tom, which will enable the characterization and isolation of important genes for plant development studies and biotechnological applications.

O tomateiro (Solanum lycopersicum L.) é um interessante modelo para estudar a base genética da capacidade de formação de órgãos adventícios, uma vez que existem variações genéticas naturais consideráveis em seus parentes selvagens. Assim, sabese que o alelo dominante Rg1, presente no braço curto do cromossomo 3 de S. peruvianum, confere alta capacidade de regeneração de gemas caulinares. Usando uma coleção de 50 linhas de introgressão (ILs), cada uma contendo um pequeno segmento cromossômico de S. pennellii LA716 introgredido e mapeado na cultivar M82, foram realizados testes com explantes cotiledonares com 12 dias de idade cultivados em meio MS contendo 5,0 M BAP, e encontramos uma alta capacidade de regeneração de gemas caulinares nas IL3-2, IL6-1, IL7-1, IL 8-3, IL-9-1 e IL10-2. Isto significa que S. pennellii provavelmente possua alelos com capacidade superior para a regeneração in vitro nessas regiões cromossômicas, incluindo um possível novo alelo para Rg1 na IL3-2. Plântulas em F1 do cruzamento entre Micro-Tom x ILs e ILs x ILs provaram que a capacidade de regeneração de gemas caulinares foi dominante nas ILs 3-2, 6-1, 7-1 e 8-3, e que a capacidade de regeneração das IL8-3 aumentou a das outras ILs, comportando-se de uma maneira aditiva. Uma vez que as ILs 3-2, 7-1, 8-3 e 10-2 também aumentaram a formação de raízes em meio MS contendo 0,4 M ANA, elas podem apresentar novos alelos que controlam a fase de competência, estando aptas a assumir diferentes destinos celulares, ao invés da indução de um órgão específico. Também realizamos a introgressão dos alelos selecionados para o modelo genético Micro-Tom, o qual proporcionará a caracterização e isolamento de genes importantes para estudos de desenvolvimento de plantas e aplicações biotecnológicas. / Tomato (Solanum lycopersicum L.) is an attractive model to study the genetic basis of adventitious organ formation capacity, since there is considerable natural genetic variation in its wild relatives. Accordingly, it is known that the dominant Rg1 allele, present in the short arm of S. peruvianum chromosome 3, confers high shoot regeneration capacity. Using a set of 50 introgression lines (ILs), each containing small a chromosomal segment of S. pennellii LA716 introgressed and mapped into the tomato cultivar M82, we found a high shoot regeneration capacity for IL3-2, IL6-1, IL7-1, IL 8-3, IL-9-1 and IL10-2, when 12-days-old cotyledon explants were cultivated in MS medium containing 5.0 M BAP, suggesting that. S. pennellii might present superior alleles for in vitro regeneration in such chromosomal regions, including a possible novel allele for Rg1 in IL3-2. F1 seedlings from the crosses Micro-Tom x ILs and ILs x ILs demonstrated that the shoot regeneration capacity of the ILs 3-2, 6-1, 7-1 and 8-3 was dominant and that the regeneration ability of IL8-3 enhanced that of the other ILs in an additive manner. Since ILs 3-2, 7-1, 8-3, and 10-2 also exhibited enhanced root formation on MS medium containing 0.4 M NAA, these segments might contain novel alleles controlling the competence to assume distinct cell fates, rather than the induction of a specific organ. We also performed the introgression of such alleles into the genetic model system Micro-Tom, which will enable the characterization and isolation of important genes for plant development studies and biotechnological applications.