Validation of Responsive Genes to Drought Stress in Two Contrasting Cultivars of Sugarcane

Sugarcane is a major crop worldwide, raw material for sugar and ethanol production. Drought is on of the most limiting factor that affects sugarcane productivity. In order to understand the mechanisms of drought response, field and greenhouse essays were conducted with two drought-contrasting sugarcane genotypes (IACSP94-2094/tolerant and IACSP97-7065/sensitive). A microarray analysis, conducted with 14,522 genes using material grown on field, and a global gene expression analysis performed by RNAseq with plants grown in greenhouse have both identified several genes that are up/down-regulated under drought stress. Among these, nine genes (presented in both assays) were selected to be validated by qPCR using leaves.  Four genes (Water Stress, Hormone Biosynthesis, Unknown1 and Unknown2) showed higher levels of transcripts in IACSP97-7065 in greenhouse, while levels in IACSP94-2094 were higher on field. Dehydrin and Cell Cycle genes showed the highest expression levels in sensitive genotype in both assays. The Stress-responsive gene was more expressed in the greenhouse trial being up-regulated on sensitive and down-regulated on tolerant genotype for maximum drought stress. The Unknown3 gene expression profiles were equal in both assays in both genotypes. The Unknown4 gene showed higher expression in IACSP97-7065 at early drought stress, while IACSP94-2094 showed gradual increase  on transcripts levels toward to maximum drought stress. The genes with greatest differences in expression profile will be used for functional analysis using transgenic rice. The identification and characterization of genes associated with response to stress are crucial for the development of new varieties with improved tolerance.

Financial support: FAPESP (2011/50661-8), CNPq.