Transcriptomic analysis of sorghum genotypes in response to drought stress

Drought is a major limiting factor of crop yields. In response to drought, plants reprogram their gene expression, which ultimately regulates a multitude of biochemical and physiological processes. The timing of this reprogramming and the nature of the drought-regulated genes in different genotypes are thought to confer differential tolerance to drought stress. At the molecular level, the responses include gene regulation at the transcriptional level. Sorghum is a highly drought-tolerant crop and has been increasingly used as a model cereal to identify genes that confer tolerance. Also, there is considerable natural variation in resistance to drought in different sorghum genotypes. Here, we performed transcriptomic analysis in seedlings of sorghum genotypes that are either drought-resistant or drought-sensitive to identify drought-induced changes in gene expression that are unique to drought-resistant genotypes of sorghum. Our analysis revealed about 180 drought-regulated genes only in drought-resistant genotypes and most of these (over 70%) are up-regulated in response to drought. Among these, about 70 genes are novel with no known function and the remaining are transcriptions factors, signaling and stress-related proteins implicated in drought tolerance in other crops. This study revealed a set of genes including many genes encoding uncharacterized proteins that are associated with drought tolerance at the seedling stage.