Comparative Analysis of Water Stress-Responsive Transcriptomes in Drought-Susceptible and -Tolerant Wheat (Triticum aestivum L.)

To understand better the mechanisms that regulate the water stress response in wheat, we conducted a comparative analysis of transcript profiles in roots from two wheat genotypes - drought-tolerant 'Luohan No. 2' (LH) and drought-susceptible 'Chinese Spring' (CS). In LH roots, 3831 transcripts displayed changes in expression of at least two-fold over the well-watered control when drought treatment was applied. Of these, 1593 were induced while 2238 were repressed. Relatively fewer transcripts were drought-responsive in CS; i.e., 1404 transcripts were induced and 1493 were repressed. In common between LH and CS, 569 transcripts were induced and 424 transcripts were repressed. In all, 689 transcripts (757 probe sets) identified from LH and 537 transcripts (575 probe sets) from CS were annotated and classified into 10 functional categories. Among those annotated transcripts from LH and CS that had fold-change ratios of at least 4, 92 induced transcripts were common to both, while 23 transcripts were specifically induced in LH. Gene ontology analysis of these induced genes showed highly significant enrichment for multiple terms related to abiotic stimuli, organic acid biosynthesis, and lipid metabolism. This suggests that these gene groups play important roles during the stress response in LH and CS, and might also be responsible for differences in drought tolerance between those genotypes.