| Dehydrin proteins are produced in a wide variety of plant species in response to environmental stresses associated with low temperature or dehydration and during developmental processes like seed maturation. The precise biochemical function of dehydrins remains unclear although recent genetic and biochemical studies indicate that they may act as lipid-associated stabilizers or protectants. If this hypothesis is proven true, the implications for dehydrins in crop improvement are immense.; The studies described here sought to identify and characterize members of the dehydrin gene family of maize. Identification entailed the cloning and sequencing of a dehydrin gene while characterization included a description of the following: allelic variation at each locus, patterns of gene expression and protein accumulation, and putative orthologous genes in other species. A total of five dehydrin genes were examined: dhn1, dhn2, dhn3, dhn4, and dhn6.; For each gene, alleles from maize and Teosinte were characterized. The allelic differences in coding regions are typical of dehydrins, occurring as either relatively small variations or as large blocks of amino acids. The effect of these differences on protein function is unknown, but in the case of dhn1, two small variations in amino acid sequence seem to significantly alter protein conformation in the presence of SDS.; Gene expression and protein accumulation of these dehydrins is generally responsive to osmotic stress (water deprivation or low temperature) or exogenous ABA treatment. Tissue-, stress-, development-, and genetic background-specific patterns of gene expression were all observed. Variations in the promoter regions of dhn1, dhn2, and dhn6 are associated with, but do not explain, the differences in gene expression patterns.; With every gene except dhn2, putative orthologous genes were identified in other species. The greatest similarity across species occurs in the conserved amino acid motifs shared by the members of this gene family. Gene expression of the putative orthologs did not always correlate with that observed in maize, indicating that there may be species-specific control mechanisms.; Map position of the maize dehydrin genes revealed several associations with QTL intervals for adaptive phenotypes. The dhn1 locus, for example, coincides with a maximum likelihood peak for cell membrane stability under water stress and heat stress. |
