Integrative Analysis of DNA Methylome and Transcriptome Reveals the Mechanism of Heat Tolerance in Non-heading Chinese Cabbage

Heat stress profoundly affects the growth and development
of non-heading
Chinese cabbage (NHCC) and usually results in great losses in yield
and quality. In this study, we observed a significant increase in
CHH methylation, specifically within gene promoter regions, in NHCC
upon heat stress exposure. Furthermore, application of DNA methylation
inhibitor 5-azacytidine was found to significantly exacerbating heat
stress-induced NHCC wilting. Integrative analysis of DNA methylome
and transcriptome identified several heat stress-inhibited regulators,
such as IQD21, SMR1, and PCR2, which negatively regulates the heat tolerance, and
silencing these genes significantly enhanced the heat tolerance of
NHCC. Our findings demonstrated that heat stress triggers hypermethylation
of CHH within promoters of some negative heat stress regulators, thus
improving the heat adaptation of NHCC. These findings provide new
insights into the mechanism of NHCC adapting to heat stress and suggest
a crucial role of DNA methylation in regulating the heat tolerance
of NHCC.