Caracterização preliminar de genes myb no genoma de eucalyptus spp

Abstract

Transcription factors are important regulators of gene expression that contains a binding domain that recognizes DNA in a specific manner and regulate the frequency of initiation of transcription by binding to promoters of target genes. Based on the similarity of the DNA binding domain, these proteins are grouped into different families. In plants, the MYB family of transcription factors is one of the largest and its members have been linked to different biological and biochemical processes, such as the control of cell morphogenesis, including the development of trichomes, roots and petals. Members of this family of transcription factors also act in the control of metabolism, particularly in regulating the synthesis of phenylpropanoids such as flavonoids, anthocyanins and lignins. Some members are also involved in regulating the response to phytohormones, including abscisic acid and gibberlins and also in response to environmental signals like light and availability of water. Some members of the R2R3-MYB subfamily has the ability to bind to AC elements that are commonly present in the promoters of genes participating in lignin biosynthesis, regulating specific steps of the biosynthesis of these molecules. As part of the data mining efforts of the vast amount of information available from Eucalyptus genome projects, this work performed the preliminary identification and annotation of transcription factors of the MYB family in the genome of Eucalyptus species in a attempt to identify those genes whose products are linked to lignin synthesis. Orthologous relationships between myb genes of Eucalyptus and those of other species described in the literature were inferred using phylogenetic analyses tools, allowing the identification of its putative functions. The evaluation of the expression profiles of 21,442 unigenes developed under the Genolyptus project allowed the investigation of the expression patterns of myb genes in two Eucalyptus species (E. grandis and E. globulus) and plant tissues (leaf and xylem). We also tried to integrate the information provided by published genetic maps of microsatellite markers containing QTLs for lignification with data from the Eucalyptus genome sequencing project. Co-localization of myb genes with QTLs for these characters has allowed the identification of myb genes of interest for future studies in functional genomics. We identified 212 genes belonging to the MYB family of transcription factors in the genome of different species of Eucalyptus. Each of these genes was submitted a process of manual annotation, and 177 of these were classified as myb-R2R3, and characterized in terms of its ultra-structure of introns and exons. The analysis of the results obtained by the use of three different methodologies: molecular phylogeny, analyses of expression and co-localization with QTLs, allowed the identification of candidate genes that are likely involved in the control of lignin content and quality in Eucalyptus. EucMYB_024, EucMYB_032, EucMYB_044, EucMYB_046, EucMYB_050 and EucMYB_068 showed evidence under the three methodologies that suggest they are involved in an important way in the process of xylogenesis in Eucalyptus. The results herein are useful in allowing the identification of target genes for future studies in functional genomics. Apparent functions were associated with these six genes. The understanding of their role in the development of Eucalyptus wood will be effectively established in future studies of genetic transformation, where the effects of overexpression and silencing of these genes may be assessed.