Transcriptional patterns and histone modification signatures reveal dehydration memory behaviour in seedlings of Gossypium hirsutum

In nature, plants often experience recurring stress conditions. Some plants have evolved a memory response, which shows an enhanced reaction upon subsequent stress. However, whether cotton (Gossypium hirsutum L.) exhibits dehydration stress memory and the underlying mechanisms have remained unclear. Here, we characterized the responses to recurring dehydration stress in cotton seedlings from physiological changes, gene expression patterns and histone modification levels. Our results showed that short-term dehydration stress memory could develop in cotton seedlings. Transcriptome analysis identified 602 transcriptional dehydration memory genes (DMGs), and these genes could be divided into four distinct response patterns. A homology analysis indicated that conservation and species-specific memory responses existed between cotton and other plants. Chromatin immunoprecipitation - qPCR results revealed that the transcriptional behaviour of [+/+] memory genes was related to the retention of increased H3K4me3 levels during the recovery stage and that H3K4me3 could act as a memory mark at the [+/+] dehydration memory genes in cotton. A virus-induced gene silencing assay indicated that the histone demethylase gene GhJMJ17-A/D may participate in the transcriptional behaviour of [+/+] memory genes in cotton. These results will improve the understanding of the mechanisms of formation and maintenance of dehydration stress memory in plants and will be useful for the improvement of cotton and other crops.