Identification of Water Deficit Stress Upregulated Genes in Sugarcane

Sugarcane represents an important renewable source among biofuel crops with high capability to assimilate carbon among the C4 plants. Limited availability of freshwater renders this crop uneconomical, warranting the necessity for the development of varieties with higher water use efficiency and tolerant to water deficiency stress. Sugarcane variety cv. Co740 was subjected to varied levels of water deficiency stress to isolate transcripts differentially expressed to the imposed stress. The leaf relative water content was used as a measure to estimate the stress response. PCR-based cDNA suppression subtractive hybridization technique was applied to construct forward subtracted library for differentially expressed genes under stress. Dot blot-selected 158 clones showing elevated response were sequenced, of which 62% resembled similarity with known functional genes, 12% with hypothetical proteins of plant origin, while 26% represented new unknown sequences. Annotation of these differentially expressed sequence tags (ESTs) in the moderately water deficit stress-tolerant cultivar predicted that most of them encoded proteins involved in cellular organization, protein metabolism, signal transduction, and transcription. Further, semi-quantitative reverse transcriptase PCR carried out for five genes projected the involvement of these ESTs in stress alleviation/tolerance. Results from this study may help in targeting useful genes for improving drought tolerance in sugarcane and other grasses.