H3K4me2, H4K5ac and DNA methylation function in short- and long-term heat stress responses through affecting the expression of the stress-related genes in G. hirsutum

Abstract

High temperature or heat stress (HS) is becoming a major threat to plant growth and crop production due to global warming. Plant adaptation to HS is markedly affected by epigenetic modifications like histone modifications and DNA methylation. However, the roles of the epigenetic modifications in modulating the responses to HS in cotton seedlings are largely unknown. In this study, the effects of short- and long-term HS on seedling growth, and the functions of histone modifications and DNA methylation in cotton responding to HS were investigated. The results showed that HS led to marked inhibition of growth, accompanied with changes in the transcript abundances of many HS-related genes and those in the contents of H3K4me2 and H4K5ac. Moreover, changes in H3K4me2 and H4K5ac levels were associated with those in the expression levels of multiple HS-responsive genes including GhHSFA1a (Heat shock factor A1a), GhHSFA2, GhHSP3 (Heat shock protein 3), GhRBCS (Small subunit of rubisco), GhERF1A (Ethylene response factor 1A) and GhHXK1 (Hexokinase 1) under high temperature stress. Also, alterations in DNA methylation levels were associated with those in the expression levels of GhHSFA1a upon HS. ChIP-qPCR results revealed that H3K4me2 levels elevated upon short-term HS, and H4K5ac levels raised during the whole HS process, particularly upon long-term HS. Virus-induced gene silencing (VIGS) experiments demonstrated that GhHSFA1a and GhHSFA2 positively, and GhERF1A and GhHXK1 negatively regulated HS tolerance in cotton. Collectively, these results suggest that H3K4me2, H4K5ac and DNA methylation modulate the expression of the HS-related genes, contributing to thermotolerant regulation in G. hirsutum.