Fabiano Vinagre

Signal transduction-related responses to phytohormones and environmental challenges in sugarcane

BackgroundSugarcane is an increasingly economically and environmentally important C4 grass, used for the production of sugar and bioethanol, a low-carbon emission fuel. Sugarcane originated from crosses of Saccharum species and is noted for its unique capacity to accumulate high amounts of sucrose in its stems. Environmental stresses limit enormously sugarcane productivity worldwide. To investigate transcriptome changes in response to environmental inputs that alter yield we used cDNA microarrays to profile expression of 1,545 genes in plants submitted to drought, phosphate starvation, herbivory and N2-fixing endophytic bacteria. We also investigated the response to phytohormones (abscisic acid and methyl jasmonate). The arrayed elements correspond mostly to genes involved in signal transduction, hormone biosynthesis, transcription factors, novel genes and genes corresponding to unknown proteins.ResultsAdopting an outliers searching method 179 genes with strikingly different expression levels were identified as differentially expressed in at least one of the treatments analysed. Self Organizing Maps were used to cluster the expression profiles of 695 genes that showed a highly correlated expression pattern among replicates. The expression data for 22 genes was evaluated for 36 experimental data points by quantitative RT-PCR indicating a validation rate of 80.5% using three biological experimental replicates. The SUCAST Database was created that provides public access to the data described in this work, linked to tissue expression profiling and the SUCAST gene category and sequence analysis. The SUCAST database also includes a categorization of the sugarcane kinome based on a phylogenetic grouping that included 182 undefined kinases.ConclusionAn extensive study on the sugarcane transcriptome was performed. Sugarcane genes responsive to phytohormones and to challenges sugarcane commonly deals with in the field were identified. Additionally, the protein kinases were annotated based on a phylogenetic approach. The experimental design and statistical analysis applied proved robust to unravel genes associated with a diverse array of conditions attributing novel functions to previously unknown or undefined genes. The data consolidated in the SUCAST database resource can guide further studies and be useful for the development of improved sugarcane varieties.

Expression of sugarcane genes induced by inoculation with Gluconacetobacter diazotrophicus and Herbaspirillum rubrisubalbicans

Several Brazilian sugarcane varieties have the ability to grow with little addition of inorganic nitrogen fertilizers, showing high contributions of Biological Nitrogen Fixation (BNF). A particular type of nitrogen-fixing association has been described in this crop, where endophytic diazotrophs such as Gluconacetobacter diazotrophicus and Herbaspirillum spp. colonize plant tissues without causing disease symptoms. In order to gain insight into the role played by the sugarcane in the interaction between this plant and endophytic diazotrophs, we investigated gene expression profiles of sugarcane plants colonized by G. diazotrophicus and H. rubrisubalbicans by searching the sugarcane expressed sequence tag SUCEST Database (http://sucest.lad.ic.unicamp.br/en/). We produced an inventory of sugarcane genes, candidates for exclusive or preferential expression during the nitrogen-fixing association. This data suggests that the host plant might be actively involved in the establishment of the interaction with G. diazotrophicus and H. rubrisubalbicans.

Gluconoacetobacter diazotrophicus Elicitate a Sugarcane Defense Response Against a Pathogenic Bacteria Xanthomonas albilineans

A new role for the plant growth-promoting nitrogen-fixing endophytic bacteria Gluconacetobacter diazotrophicus has been identified and characterized while it is involved in the sugarcane-Xanthomonas albilineans pathogenic interactions. Living G.diazotrophicus posse and/or produce elicitor molecules which activate the sugarcane defense response resulting in the plant resistance to X.albilineans, in this particular case controlling the pathogen transmission to emerging agamic shoots. A total of 47 differentially expressed transcript derived fragments (TDFs) were identified by cDNA-AFLP. Transcripts showed significant homologies to genes of the ethylene signaling pathway (26%), proteins regulates by auxins (9%), ß-1,3 Glucanase proteins (6%) and ubiquitin genes (4%), all major signaling mechanisms. Results point toward a form of induction of systemic resistance in sugarcane-G. diazotrophicus interactions which protect the plant against X. albilineans attack.

Induced-resistance in sugarcane against pathogenic bacteriaXanthomonas albilineans mediated by an endophytic interaction

Inductions of systemicresistance in sugarcane-G. diazotrophicus interactions which protect the plants againstX. albilineans attack have been demonstrated.G. diazotrophicus activates the sugarcane defense response resulting in the plant resistance toX. albilineans, in this particular case controlling the pathogen transmission to emerging agamic shoots. A total of 47 differentially expressed transcript derived fragments (TDFs) were identified by cDNA-AFLP. Transcripts showed significant homologies to genes of the ethylene signaling pathway (26%), proteins regulates by auxins (9%), β-1,3 Glucanase proteins (6%) and ubiquitin genes (4%), all major signaling mechanisms. A new role for the plant growth-promoting nitrogen-fixing endophytic bacteriaGluconacetobacter diazotrophicus has been identified and characterized while it is involved in the sugarcane-Xanthomonas albilineans pathogenic interactions.