In the yeast Saccharomyces cerevisiae, the molecular chaperone HSP26 has the remarkable ability to sense increases in temperature directly and can switch from an inactive to a chaperone-active state. In this report, we analyzed the effect of expression of HSP26 in Arabidopsis thaliana plants and their response to high temperature stress. The hsp26 transgenic plants exhibited stronger growth than wild type plants at 45 °C for 16 h. The chlorophyll content and chlorophyll fluorescence decreased much more in wild type than in transgenic plants. Moreover, the transgenic plants had higher proline and soluble sugar contents, and lower relative electrical conductivity and malondialdehyde contents after high temperature stress. Furthermore, we found that over-expression of HSP26 in Arabidopsis increased the amount of free proline, elevated the expression of proline biosynthetic pathway genes and therefore enhanced Arabidopsis tolerance to heat stress.Additional key words: high temperature stress, transgenic plants, yeast gene.

Cytosolic glyceraldehyde-3-phosphate dehydrogenase (GAPC) catalyzes a key reaction in glycolysis and encoded by a multi-gene family which showed instability expression under abiotic stress. DNA methylation is an epigenetic modification that plays an important role in gene regulation in response to abiotic stress. The comprehension of DNA methylation at promoter region of TaGAPC1 can provide insights into the transcription regulation mechanisms of plant genes under abiotic stress. In this study, we cloned TaGAPC1 genes and its promoters from two wheat genomes, then investigated the expression patterns of TaGAPC1 under osmotic and salinity stress, and analyzed the promoter sequences. Moreover, the methylation patterns of promoters under stress were confirmed. Expression analysis indicated that TaGAPC1 was induced inordinately by stresses in two wheat genotypes with contrasting drought tolerance. Several stress-related cis-acting elements (MBS, DRE, GT1 and LTR et al.) were located in its promoters. Furthermore, the osmotic and salinity stress induced the demethylation of CG and CHG nucleotide in the promoter region of Changwu134. The methylation level of CHG and CHH in promoter of Zhengyin1 was always increased under stresses, and the CG contexts remained unchanged. The cytosine loci of stress-related cis-acting elements also showed different methylation changes in this process. These results provide insights into the relationship between promoter methylation and gene expression, promoting the function investigation of GAPC.

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