Heat Shock Proteins Expression Is Regulated by Promoter CpG Methylation/demethylation under Heat Stress in Wheat Varieties

Saqer S. Alotaibi, Ahmed M. El-Shehawi and Mona M. Elseehy

Background and Objective: Heat shock proteins are induced by high temperature and other environmental stimuli to protect cellular proteins. Despite extensive research on the molecular response to heat stress, the effect of high temperatures on genes and pathways remains unclear. This study investigated the expression of the HSP17 gene in nine Egyptian wheat varieties and the role of HSP17 promoter CpG methylation in the regulation of HSP17 under high temperature. Materials and Methods: The HSP17 expression was investigated by using semi-quantitative PCR analysis. Methylation at the HSP17 promoter proximal region was analyzed using bisulphite sequencing and CpG viewer software. Results: Under normal conditions, HSP17 and methyltransferase 3 (MET3) exhibited similar expression levels in the 9 studied varieties. After exposure to high temperature, the expression level of HSP17 in Giza155 was barely detected. Among the nine varieties, the expression level of HSP17 was highest in Giza168 (11.3 folds of Giza155). Analysis of methylation of 14 CpG islands at the HSP17 proximal promoter sequence showed that methylation of 10 CpG islands differed only by 10-20%, whereas methylation at the other 4 CpGs differed by 56.7-60%. The high expression of HSP17 in Giza168 in response to high temperature was associated with low methylation of four CpGs and low MET3 expression, whereas low expression of HSP17 in Giza155 was associated with high methylation and high MET3 expression. Conclusion: The results can aid the development of next-generation approaches to the evaluation of commercial wheat varieties and the development of next-generation approaches to plant breeding employing epiallele integration.

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