| To identify novel dehydration responsive genes, large scale transcriptional profiling of water stressed roots of a drought susceptible hexaploid wheat (Triticum aestivum) genotype, Opata, and its drought tolerant, synthetic derivative (pedigree: 'Altar 84/ Aegilops squarrosa (TAUS)//Opata') were conducted. I also compared physiological and morphological parameters of these genotpyes (i.e. relative water content, photosynthetic rate, water loss rates, cell membrane stability, and root length) to further demonstrate the differences in their responses to water stress. One of the novel dehydration responsive genes I identified had increased transcript abundance under dehydration stress in both genotypes. This transcript encodes a predicted 8 kDa, 74 amino acid protein, with a theoretical pI 10.9, and has been previously called "Little Protein 1" (LiP). Further experiments demonstrated that LiP is induced under a variety of environmental conditions (cold, drought, osmotic, and salt) in roots of Arabidopsis . I also showed that its expression is not dependent on ABA biosynthesis, ABA perception, or SOS pathways. Transient and stable translational expression of GFP fused LiP in Nicotiana benthamiana and in Arabidopsis thaliana suggested that LiP is localized in the plasma membrane. In order to develop antibodies and to perform future biochemical assays and structural studies, I expressed this protein in E. coli .The pathogenesis-related 10 (PR-10) family also defines a group of small proteins whose function is only starting to be understood. To characterize the PR-10 gene family in wheat, I conducted phylogenetic analyses, which demonstrated that the wheat PR-10 gene family is comprised of at least two distinct types of PR-10 genes, with a third type showing similarity to rice and maize allergens. By qRT-PCR experiments, I showed that members of the two main wheat PR-10 clades respond differentially to drought stress. Clade 1 PR-10 showed the greatest basal expression in flag leaves but it was not induced significantly under drought stress whereas, Clade 2 PR-10 predominantly expressed in roots and its expression in roots and leaves increased under drought stress. The expression of wheat PR-10s did not correlate with drought tolerance of a selected number of genotypes. These results will help conventional and molecular breeders to further investigate and identify expression quantitative trait loci (eQTLs) and make use of them in their breeding programs. |
