Transcriptional profiling of drought response in Sorghum bicolor (L.) Moench

The identification of genetic factors underlying the complex responses of plants to drought stress provides a solid basis for improving drought resistance. The stay-green character in sorghum {Sorghum bicolor L, Moench) is a postflowering drought resistance trait, which makes plants resistant to premature senescence under drought stress during the grain filling stage. The objective of this study is to integrate phenotypic analysis, physiological data, and expression profile data to further characterize the genes controlling the stay-green trait. A detailed description of the stay-green trait, phenotypic characterization, and expression profiling data will be presented.

To accomplish the objective, two drought-induced, subtracted cDNA libraries were constructed using the B35 (post-flowering drought resistant/staygreen parent) and Tx7000 (post-flowering drought-susceptible parent). 10,300 cDNAs were sequenced, representing 3075 5' sequences, 4811 3' sequences, and 2414 sequences for both 5' and 3' clone ends. Analysis of the contiguous sequences of the 3' clones shows this collection represents 3235 unique genes. All sequences were analyzed for those unique to specific stressed parent lines and assembling a non-redundant collection for gene expression profiling studies. Tissue for gene expression studies was collected from field trials and greenhouse experiments from B35, Tx7000, and inbred lines containing specific QTLs for the stay-green trait. Physiological analyses of stressed plants included gas-exchange analysis for photosynthesis, transpiration, and stomatal conductance, as well as leaf green-ness, and chlorophyll content.