Durante esse trabalho de pesquisa verificou-se que a aquisição de competência para conversão de ápices radiculares de Catasetum fimbriatum em gemas caulinares aumentava à medida que as plantas envelheciam. Esse processo esteve relacionado ao estabelecimento do crescimento determinado das raízes e com a parada da atividade e re-organização estrutural do meristema apical radicular (MAR). Este, quando ainda jovem e destituído de competência para a conversão em gemas, apresentava uma organização do tipo fechada, ao passo que em estágios avançados do envelhecimento este padrão transformou-se em um tipo aberto, marcado pela diferenciação e predominância de células parenquimáticas. Tais alterações, aparentemente, ocorreram com a concomitante perda das características e funções do centro de quiescente (CQ). De maneira complementar, constatou-se que a aquisição de competência do MAR para conversão em gemas estava correlacionada a uma série de alterações metabólicas, as quais, supostamente, participaram de uma condição fisiológica favorável a esse processo. Com base no conjunto de dados obtidos, pode-se observar que os teores endógenos de importantes participantes na progressão de divisões celulares, tais como auxinas, citocininas e formas reduzidas de ascorbato e glutationa tenderam a diminuir durante o envelhecimento das raízes. Por outro lado, durante esse mesmo período, o conteúdo de alguns hormônios envolvidos na sinalização de condições de estresse ou diferenciação celular, tais como etileno, ácido abscísico e giberelinas tenderam a aumentar. As concentrações relativas de importantes sinalizadores secundários, tais como óxido nítrico e cálcio citossólico também apresentaram aumento conspícuo na região do MAR durante o envelhecimento. Agregando elementos a estas constatações, verificou-se que o transporte polar de auxina seria um importante sinal posicional para a manutenção das características e função do MAR, uma vez que o seu bloqueio em plantas jovens foi suficiente para causar a aquisição da competência do MAR, no entanto, o processo de conversão não era consolidado enquanto os ápices radiculares permaneceram ligados às plantas. A aplicação de etileno em plantas jovens, por sua vez, desencadeou efeitos similares; no entanto, além de induzir a competência, esse hormônio também proporcionou a conversão dos MARs em gemas via aumento nos teores endógenos de citocininas. O tratamento de ápices radiculares jovens com diferentes tipos de citocininas revelaram que citocininas do tipo isopenteniladenina (iP e iPR) mostraram-se mais de perto relacionadas à retenção de características radiculares, ao passo que as do tipo zeatina (Z e ZR) apresentou maior influência e presença em condições em que as características radiculares foram perdidas. Por outro lado, a aplicação de substâncias moduladoras do balanço redox em ápices radiculares jovens mostrou que o estresse oxidativo proporcionou a aquisição de competência do MAR para conversão em gemas. Essa mesma tendência foi observada com a aplicação de concentrações relativamente elevadas de substâncias indutoras da elevação dos teores de óxido nítrico e cálcio citossólico nos tecidos. Os ápices radiculares com competência parcialmente estabelecida, analisados logo nas primeiras horas após o isolamento, revelaram que sua separação da planta-mãe acelerava as mudanças morfológicas que naturalmente ocorrem no MAR em estágios avançados do envelhecimento. Durante esse mesmo período, verificou-se uma queda rápida nos teores endógenos de citocininas (principalmente do tipo iP), proporcionando a predominância de citocininas do tipo Z durante a maior parte do primeiro dia de isolamento dos explantes, a qual coincidiu com a mudança no padrão de organização do MAR do tipo intermediário-aberto para o totalmente aberto. O avanço das modificações no ápice radicular após esse período desencadeou o estabelecimento do meristema caulinar, cujo evento esteve relacionado a uma tendência de aumento nos teores de citocininas e de ascorbato após o primeiro dia de isolamento. Dessa forma, os estágios mais avançados do envelhecimento radicular, bem como a separação de ápices radiculares com competência parcialmente estabelecida, parecem desencadear e aumentar a competência do MAR para conversão por meio de modificações morfológicas e fisiológicas muito similares nos ápices radiculares. Essas alterações envolveram a perda das características radiculares, a qual parece depender de alterações no controle exercido pelo CQ sobre o desenvolvimento das demais células no MAR. Esses eventos na região do CQ se revelaram condição sine qua non para a complementação da aquisição de competência do MAR, sendo esta dependente da intensidade das perturbações sobre o controle da organização do MAR. Dessa forma, a conversão do meristema apical radicular de C. fimbriatum em gemas caulinares parece decorrer da formação de um novo grupo de células na antiga região do CQ do MAR alterado. Essas células pareceram competentes para responder a diferentes estímulos que as direcionariam a uma nova rota do desenvolvimento que, nesse caso, seria o estabelecimento de um meristema caulinar com conseqüente desenvolvimento de uma gema vegetativa. / During this research work, it was noticed that competence acquisition for the conversion of Catasetum fimbriatum root tips into buds was related to the plant ageing. This process seems to be coupled with the establishment of the determinate root growth and with the cessation in the activity and structural re-organization of the root apical meristem (RAM). Young and non-competent root tips showed a closed RAM architecture, and the ageing process stimulated the establishment of an open organization in the RAM, as indicated by a higher level of differentiation and a predominance of parenchymatic cells in the old root apices. These alterations were concomitant with the modifications on the characteristics and functions of quiescent center (QC). In agreement with these observations, the competence acquisition to the conversion of the MAR into buds was linked to a series of metabolic alterations, which probably play a role in this process. Based on the data obtained, it was observed that the endogenous levels of important components of the cell division progression, such as auxins, cytokinins and the reduced forms of ascorbate and glutathione showed a tendency of decrease during the root ageing. On the other hand, during this same period, the content of some hormones involved in signalling events of stress conditions or cellular differentiation, such as ethylene, abscisic acid and gibberellins exhibited a pattern of increase. The relative concentrations of important second messengers, such as nitric oxide and cytosolic calcium also displayed a marked increased in the RAM region during the ageing. Additionally, it was noticed that the auxin polar transport represents an important positional signal for the maintenance of the RAM characteristics and functions, once treatments that blocked the transport of this hormone promoted the MAR competence acquisition even in young plants, although, the conversion process did not complete while the root tips were maintained attached to the plants. The treatment of young plants with ethylene, on the contrary, caused similar effects; however, besides inducing the competence, this hormone also promoted the RAM conversion into buds via the elevation in the endogenous levels of cytokinins. The treatment of young root tips with different types of cytokinins indicated that iP-type cytokinins (iP and iPR) were more closely associated to the preservation of the root characteristics, while the Z-type cytokinins (Z and ZR) showed a higher importance when the root characteristics were lost. Furthermore, the treatment of young root apices with compounds that cause alterations in the cellular redox status indicated that the oxidative stress stimulated the competence acquisition for the RAM conversion into buds. This same tendency was observed with the application of relatively high concentrations of compounds that induce elevations in the levels of nitric oxide and cytosolic calcium in the tissues. The analyses carried out during the first hours after the isolation of partially competent root apices indicated that the detachment of the root tips from the original plants accelerated the morphological modifications that naturally occur at advanced stages of ageing. During this same period, it was observed a rapid decrease in the endogenous levels of cytokinins (specially of the iP-type), leading to a predominance of the Z-type cytokinins during the first day after the isolation of the explants, which coincided with the alteration of the RAM architecture from the intermediate-open type to the completely open type. After the first day of isolation, the progress in the root apices modifications resulted in the establishment of the shoot meristem, which was accompanied by an elevation in the endogenous levels of cytokinins and ascorbate. Therefore, advanced stages of root ageing, as well the isolation of the partially competent root apices, seem to increase the competence for the RAM conversion into buds via similar morphological and physiological changes in the root apices. These alterations involved the loss of the root characteristics, which possibly resulted from modifications in the control of the QC on the development of the other cells in the RAM. These events in the QC represent a sine qua non condition for the completion of the MAR competence acquisition, which is affected by the intensity of the perturbations on the control of the RAM organization. Therefore, the conversion of root apical meristem of C. fimbriatum into buds probably results from the formation of a new group of cells in the region of the QC of the altered RAM. These cells seem to be competent to respond to different stimulus that would directionate them to a new developmental route that, in this case, consists in the establishment of a shoot meristem.

The shoot apical meristem (SAM) is the structure that shapes the aerial architecture of the plant, by producing lateral organs throughout development. In the model plant Arabidopsis thaliana, the SAM is always identifiable as a characteristic dome, whether it is found in the centre of a rosette of leaves or at the tip of an inflorescence. When senescence occurs and organogenesis ceases, the now inactive SAM still retains its characteristic appearance and it is never consumed into a terminal structure, such as a flower. Mutant plants that undergo termination represent a valuable tool to understand how the SAM structure and function are maintained during plant life. The aim of this work was to investigate the dynamics of meristem development through morphological and genetic studies of three Arabidopsis mutants that exhibit distinct modes of SAM termination: distorted architecture 1 (dar1), adenosine kinase 1 (adk1) and terminal flower 2 (tfl2). The dar1 mutation is characterised by a severely distorted cellular architecture within the SAM. We propose that dar1 affects the pattern of cell differentiation and/or cell proliferation within the SAM apical dome, resulting in termination by meristem consumption. Instead, the adk1 mutation affects the organogenic potential of the SAM, without altering its structure. The adk1 mutant has increased levels of cytokinins and, as a consequence of this, cell division is enhanced and cell differentiation is prevented in the apex, causing termination by meristem arrest. Finally, tfl2 is mutated in the conserved chromatin remodelling factor HP1, a transcriptional repressor with multiple roles during plant development. The tfl2 SAM terminates by conversion into a floral structure, due to de-repression of floral identity genes. Interestingly, tfl2 mutants also show an altered response to light, an indication that TFL2 might act as a repressor also in the context of light signalling.

The aerial plant body is derived from undifferentiated cells in the shoot apical meristem that in Arabidopsis thaliana is active throughout the plant life cycle. Upon transition to flowering the activity of the meristem is altered and the meristem starts to produce secondary inflorescences and floral meristems instead of leaves. Both the activity of the meristem and the decision of when to flower are processes strictly regulated by several mechanisms. In this thesis I describe the function of two genes that are active in the regulation of meristem function and in the regulation of when to shift to reproductive development. First, the Arabidopsis gene encoding TERMINAL FLOWER2 (TFL2), homologous to HETEROCHROMATIN PROTEIN1, was isolated and characterised. Mutations in TFL2 result in plants that are dwarfed, flowers early, have reduced sensitivity to day length and terminate the inflorescence in an apical flower. As homologues from other organisms TFL2 is active in gene regulation by gene repression. I show that the gene affect flowering time by the autonomous and the photoperiod pathways, two of four floral inductive pathways. TFL2 act to repress the activity of genes that are promoters of floral meristem identity and interacts genetically with factors known to alter the chromatin state. Further tfl2 is shown to have altered levels of and response to auxin. All together this shows that TFL2 is active as a regulator of several different processes during plant development. Second, I have characterised and studied the function of three genes encoding APETALA2 LIKE proteins in Norway spruce (Picea abies). In spruce these genes are expressed in meristems and reproductive tissues. When constitutively expressed in Arabidopsis two of the genes delays flowering time and alter the function of shoot apical and floral meristems. Together this suggests a function similar to the Arabidopsis homologues.

Thalassia testudinum Banks and Solander ex König is the dominant seagrass in the Gulf of Mexico, Caribbean and the West Coast of Florida, yet little rhizome elongation, new short shoot production, or new rhizome meristem production data has been collected via direct measurement. A study of the rhizome growth of T. testudinum was completed in December 2004 in southern Tampa Bay that determined growth after 26.5 months. Two PVC planting frames each containing four rhizomes with 2 short shoots, two rhizomes with 4 short shoots, and two rhizomes with 8 short shoots were planted next to existing T. testudinum beds at 5 sites (n = 10 planting frames). The rhizome apical meristem was removed from half of each set of short shoot units on each planting frame. Plants initially lacking a rhizome meristem produced more new long shoot meristems than those planted with an intact meristem, and larger planting units produced more new rhizome meristems than smaller ones, P = 0.001 and P < 0.001, respectively. The total number of rhizome meristems per planting unit (new meristems + initial meristem) was greater in plantings initially lacking a long shoot meristem in the 2, 4 and 8 short shoot size classes. Only the two short shoot plants benefited from an intact rhizome meristem at planting time, elongating 66.4 cm versus 60.4 cm for plants initially lacking a rhizome meristem at 26.5 months. In the 4 and 8 short shoot classes, plants that lacked a rhizome meristem at planting outpaced those with a meristem, producing 192.1 and 277.9 for 4 and 8 short shoot plants compared to 120.9 cm and 177.7 cm for plants with a meristem during the same time period. The greatest growth rate increases were due to lateral branching on planting units that lacked a rhizome meristem in the two largest size classes (4 and 8 short shoots); the differences between plants with an intact rhizome meristem and those without with the size classes pooled did not prove to be statistically different, P = 0.112. Differences among the size classes were significant, however, P < 0.001. Analysis of new short shoots was analogous to the results for rhizome elongation, with the presence of an initial rhizome factor proving insignificant, P = 0.401, and the initial number of short shoots factor proving significant, P < 0.001. The rhizome growth, new short shoot production, and new rhizome meristem production data determined by direct measurements in this study appear to be the first planting unit measurements for this species under natural conditions.

In an effort to maximize yields, many soybean growers have begun moving to intensive, input-based soybean management systems. However, limited reliable information exists about the effect of these inputs on soybean yield. The purpose of this study was to evaluate the effect of individual inputs and combinations of inputs as part of high-yield management systems on soybean seed yield and to determine the effect of one of these inputs, lactofen, on soybean physiology. Small plot studies were established in nine states across the Midwest. A number of commercially available soybean inputs were evaluated individually and in combination to determine their effect on soybean yield and quality. Lactofen and comparison treatments were applied to soybeans at multiple growth stages and yield and yield components were determined. When examined across environments, input-intensive combination treatments increased soybean yields from 3.9 to 8.1 %. However, break-even economic analysis indicated that the combination (SOYA) treatments evaluated had 0% probability of breaking across a wide range of yield levels and soybean prices, due to the high input costs. The foliar insecticide showed the highest probability of breaking even across a range of yield levels and crop prices (40% to 99%). Yield increases and breakeven probabilities were generally greatest in the northern states (Minnesota, Wisconsin, Michigan) and similar in the central and southern states. Lactofen application did not kill the apical meristem and had minimal effect on yield components compared to untreated soybeans at any growth stage. Meristem removal increased node m-2 in some environments, but did not increase pods m-2 and seeds m-2 or seed yield.

Although cottonseed is an important source of oil and fiber, the development of cotton embryos has not been investigated as well as development of cotton fiber. The development of cotton embryos in late heart-stage and early cotyledonary stage is less well investigated than the first 10-14 days after anthesis, or the late stages of embryo development during seed-fill and desiccation. This analysis focused on cotton embryos in the late heart-stage and early cotyledonary stage of development (1.5-4.0 mm or about 13-18 DPA). In vitro analyses are important tools for studying embryos in isolation from the endosperm and fiber and when it is necessary to monitor the developing embryo continuously. The original goal of this work was to develop an in vitro culture method that would support continued development of excised zygotic embryos from the early cotyledonary stage into complete plants with true shoots, i.e. true leaves or visible buds and then to use this method to study aspects of developmental regulation during cotyledonary stage and the transition to later stages. Not all embryos were competent to develop true shoots (an apical bud or a leaf plus a bud) in culture. A number of cultural variables were tested and eliminated. Embryo maturity at the time embryos were excised and the presence or absence of light during the first 14 days of culture affected the competence of immature embryos to developed true shoots. The effect of light was verified in several large replicated experiments. Morphological changes occurring during in vivo development were examined microscopically. The transition from heart-stage to early cotyledonary stage and the development of the first leaf from initials to a large structure were identified. Embryonic shoot apices continued to grow in cultured 1-3 mm embryos. The size and shape of light-treated and dark-treated embryonic apices was compared. A germination test of mature seeds identified seedlings with a similar phenotype occurring at similar rates in seedlings and light-cultured embryos and possible causes were discussed.

Plant growth and development depends on controlled cell expansion. This, in itself, is determined by the plant cell wall, a structural matrix of polysaccharides encasing the plant cell. One line of investigation that has proven particularly successful in elucidating the components of the plant cell wall machinery has been the forward genetic screens of cell wall mutants. In this study, the molecular and cellular characterisation of sloughy, a cell separation mutant in Arabidopsis thaliana, was commenced. This mutant has a striking phenotype, with files of elongating epidermal cells snaking away from the adjacent epidermal cells and from the underlying cortex, loosing contact from the side walls while remaining attached at the cell ends, in a manner reminiscent of border-like cells in the root cap of arabidopsis. The sloughy mutation was fine mapped to a short region on chromosome I using high resolution melt point analysis. On sequencing all five genes in this region, a single nucleotide mutation, introducing a stop codon, was detected in exon 2 in the previously-described heat shock transcription factor SCHIZORIZA that results in a truncated protein missing several conserved domains essential for activity. SCHIZORIZA acts as a cell fate determinate in the root meristem to promote cortex fate, while suppressing epidermal and root cap fate in the mature ground tissue. Although the literature on schizoriza mutants has focused on the developing root meristem, with little documentation on the cell separation phenotype further up in the roots, the investigation of a collection of schizoriza TILLING mutants revealed that aberrant cell separation was ubiquitous to schizoriza mutants with a severely truncated protein. To investigate cell identity in the mature roots, sloughy was crossed to GAL4-GFP enhancer trap lines that act as cell-specific markers. Epidermal identity lines revealed that sloughy possessed a supernumerary ground tissue layer with epidermal identity. A cortex and endodermal line revealed that these two identities are restricted to the endodermal layer and the next ground tissue layer out. There was no indication of root cap identity in the mature root with any of the root cap lines used, although partial lateral root cap identity has been previously described in the epidermal and subepidermal cell layers in the meristem of schizoriza mutants expressing SOMBRERO-GFP, a lateral root cap-specific transcription factor. Immunolabelling of cell wall epitopes revealed that the JIM13 antibody, which specifically labels arabinogalactan-proteins in wild-type root caps, often labelled the epidermal cells and surrounding mucilage further up the in the roots of sloughy. The aberrant cell separation present in sloughy is thought to be a consequence of epidermal cells possessing partial lateral root cap identity. The data on sloughy/schizoriza is sufficient to generate a model on how a meristem developmental gene can generate a cell separation phenotype in the mature roots. Loss of SCHIZORIZA causes confused cell identity in the root meristem that results in an epidermal and subepidermal layer possessing mixed epidermal and lateral root cap identity. The distinctive properties of border-like cells in the root cap of arabidopsis have been linked to unique cell wall maturation and developmental processes, implicating the cellulases CEL3 and CEL5, the pectin glycosyltransferase QUA1, the pectin methyltransferase QUA2 and other pectolytic enzymes. The ectopic expression of these cell wall enzymes in the epidermal and subepidermal layers of sloughy roots result in reduced adhesion along the sides of the cell, while the ends remain attached, causing the observed cell separation phenotype.

O florescimento é um processo chave no desenvolvimento vegetal. A mudança de identidade do meristema apical de vegetativo para reprodutivo desencadeia reprogramação genética com efeitos em todo o corpo vegetal. Arabidopsis thaliana é conhecida como o principal modelo de estudo para esse processo apresentando até o momento cinco principais vias genéticas regulatórias. Tais vias apresentam redundância, sendo complexa a eliminação total da transição de fase nessa espécie. A via AGE, regulada pela idade da planta, tem como principais reguladores o mir156 e seus alvos diretos, os fatores de transcrição da família SPL/SBP (SQUAMOSA PROMOTER BINDING PROTEIN-like). Uma segunda via é controlada pelo fitohormônio giberelina (GA), o qual atua de maneira oposta em Arabidopsis thaliana (arabidopsis) e Solanum lycopersicum L. (tomateiro). Em tomateiro, diferentemente de arabidopsis, o cruzamento entre mutantes com conteúdo alterado de GA e plantas transgênicas superexpressando o miR156 (156OE; SILVA et al., 2014) demonstraram efeito sinérgico no atraso do tempo de florescimento. A aplicação de GA3 em plantas 156OE apresenta efeito similar aos cruzamentos citados sobre a transição do meristema apical. Em um dos cruzamentos entre mutantes da via GA e plantas 156OE, foi possível obter plantas apresentando completo bloqueio da transição de fase vegetativo-reprodutivo. A oferta extra do florígeno SINGLE FLOWER TRUSS (SFT) via enxertia não foi suficiente para restaurar a transição de fase nessas plantas, sugerindo que vias associadas à GA e AGE regulam alvos em comum, os quais podem ser independentes da regulação por SFT. Além disso, a regulação transcricional, e possivelmente pós-transcricional de alguns genes SBPs por diferentes vias associadas à GA, sugere uma complexa inter-relação entre as vias GA e AGE em tomateiro durante o florescimento. A ação combinada das vias GA e AGE foi capaz de inibir completamente o florescimento em tomateiro, regulação oposta ao verificado na planta modelo Arabidopsis thaliana. O efeito inibitório de GA sobre o florescimento é também visualizado em plantas lenhosas, sugerindo que as descobertas científicas realizadas em tomateiro podem ser expandidas para essas espécies, nas quais a experimentação é lenta e laboriosa / The flowering process is a major developmental event during the plant life cicle. The meristem identity switches from vegetative to reproductive, triggering substantial genetic modifications that affect the whole plant body. Arabidopsis thaliana is a major model for flowering with five different pathways controlling this process. These pathways are redundant, making complex the complete elimination of phase change in this species. One of the pathways is termed AGE since it is regulated by the time of development. The miR156 and its direct target SBP (SQUAMOSA PROMOTER BINDING PROTEIN-like) are the main regulators of the AGE pathway. A second pathway is controlled by the phytohormone gibberellin (GA), which acts in opposite ways when comparing Arabidopsis thaliana and tomato. In tomato, unlike Arabidopsis, the cross between mutants with altered contents of GA and transgenic plants overexpressing the miR156 (156OE; SILVA et al, 2014) showed synergistic effect in delayed flowering time. Treatments of GA3 in plants 156OE lead to similar effects visualized on the crosses above related to meristem transition. Among the crosses between GA mutants and 156OE plants, one double mutant could completely abolish the phase change in tomato. An extra offer of the florigen (SINGLE FLOWER TRUSS or SFT) by grafting experiments was unable to restore the flowering process in this double mutant. It suggests, pathways associated to GA and AGE regulate common downstream targets, which could be independent of SFT regulation. Moreover, the transcriptional regulation, and possible the post-transcriptionally regulation of some SBP targets by different pathways associated to GA, suggest a complex network between GA and AGE during the flowering in tomato. The combined action of GA and AGE pathways can complete impaired the flowering in tomato, this interaction is opposed to the model Arabidopsis thaliana. The negative effect of GA over the time of flowering is presented in wood plants, suggesting the scientific discoveries in tomato could be expanded to these species, which experiments are slow and laborious

RNA silencing is a major regulator of gene expression in plants, controlling from development to transposable element silencing and stress responses. As part of the silencing machinery, micro (mi)RNAs orchestrate silencing of their targets, either directly or through cascades of secondary small interfering (si)RNAs. To investigate the role of RNA silencing in plant immunity, I chose to focus on the miR482/2118 family, because of its diversity and presence in many plant species since the appearance of seed plants, with most genomes containing several copies, and because its members target sequences conserved in a family of disease resistance genes known Nucleotide biding site leucine-rich repeat (NLR) genes. In this dissertation, I wanted to address the extent to which the miRNA family and its derived phasiRNAs regulate expression of defence genes as well as contribute to quantitative resistance in crops. I explore the structural differences of miR482/2118 members in Solanum lycopersicum and show that they are functionally significant and affect their target preferences. My approach was based on small RNA sequencing and degradome data to characterize targets of these miRNAs, including the recently discovered tomato TAS5 locus. I also generated transgenic tomatoes constitutively expressing target mimic RNAs that sequester different miR482/2118 members. These tomato mimic RNA lines were less susceptible than their non-transgenic precursors to pathogens Phytophthora infestans and Pseudomonas syringae. Additionally, I investigated the role of small RNAs and their effector proteins during vegetative and reproductive development in tomato. I employed transcript and small RNA sequencing and CRISPR-Cas9 techniques of gene editing to investigate the impact of these factors in gamete viability and transposable element silencing in vegetative meristems. The results presented here provide new evidence about the extent that RNA silencing contributes to the regulation of vital processes in plants. My study primarily explores the extent to which structural differences between the members of the miR482/2118 family affect their range of action, and the use of target mimics against these miRNAs as biotechnological approach for enhancing disease resistance in highly bred cultivars.

Made available in DSpace on 2014-12-17T14:03:35Z (GMT). No. of bitstreams: 1 AmandaLMM_DISSERT.pdf: 1135135 bytes, checksum: 22f94cd634c60ab505070e7d4ae43900 (MD5) Previous issue date: 2010-08-31 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / In this work, we used sugarcane as a model due to its importance for sugar and ethanol production. Unlike the current plant models, sugarcane presents a complex genetics and an enormous allelic variation. Here, we report the analysis of SAGE libraries produced using the shoot apical meristem from contrasted genotypes by flowering induction (non-flowering vs. early-flowering varieties) grown under S?o Paulo state conditions. The expression pattern was analyzed using samples from S?o Paulo (SP) and Rio Grande do Norte (RN) states. These results showed that cDNAs identified by SAGE libraries had differential expression only in S?o Paulo state samples. Furthermore, the cDNA identified CYP (Citocrome P450) was chosen for in silico and genome characterization because it was found in SAGE libraries and subtractive libraries from samples from RN. Phylogenetic trees showed the relationship for these sequences. Furthermore, the qRT-PCR for CYP showed a potential role as flowering indutor for RN samples considering different isophorms. Considering the results present here, it can be consider that CYP gene may be used as molecular marker / A cana-de-a??car ? um modelo devido ? sua import?ncia na produ??o de ?lcool e a??car. Diferente de outras plantas modelo, ela apresenta um genoma complexo e muita varia??o al?lica. Foram analisadas as bibliotecas SAGE produzidas a partir de ?pices meristem?ticos de cana-de-a??car de gen?tipos tardio e precoce, quanto ao florescimento, cultivados no estado de S?o Paulo. A express?o destes cDNAs prospectados foi analisada usando amostras de S?o Paulo e do Rio Grande do Norte. Estes resultados mostraram que os genes apresentavam express?o diferencial apenas para os gen?tipos cultivados em S?o Paulo. Entretanto, o cDNA CYP (Citocromo P450), foi escolhido para uma an?lise in silico e caracteriza??o gen?tica por ter sido identificado tanto nas bibliotecas SAGE como em bibliotecas subtrativas realizadas com gen?tipos cultivados no Rio Grande do Norte. ?rvores filogen?ticas mostraram a rela??o evolutiva entre as sequ?ncias. Al?m disso, dados de qRT-PCR para CYP51 mostram um poss?vel papel indutor de flora??o nas condi??es do RN. Considerando os resultados apresentados, podemos inferir que o gene CYP51 pode ser utilizado como marcador molecular para o melhoramento cl?ssico