Histone deacetylase <i>SlHDA1</i> positively regulates temperature and waterlogging tolerance in tomato

SlHDA1, a histone deacetylase gene, plays essential roles in plant growth, development, and fruit ripening. However, little is known about how SlHDA1 affects the response to abiotic stress. We constructed a SlHDA1-RNAi vector to generate SlHDA1-RNAi transgenic lines and assessed effects of silencing of SlHDA1 in tomato on tolerance to multiple abiotic stresses: low temperature, high temperature, and waterlogging. There were severe growth impairments in SlHDA1-RNAi transgenic tomato plants under low and high temperature stress or waterlogging compared with WT plants, with significant reductions in ABA, chlorophyll, proline, and CAT activity, and elevated MDA and histone H3 acetylation. RNA-seq analysis of transgenic plants found that transcripts of genes encoding defence proteins related to responses to abiotic stress (e.g., protein detoxification and oxidase) and biotic stress (e.g., pathogenesis-related proteins) were upregulated or downregulated in SlHDA1-RNAi lines, indicating the importance of SlHDA1 in mediating stress-related gene expression. In summary, SlHDA1 functions as a stress-response gene that positively regulates both temperature and waterlogging tolerance in tomato. These findings highlight its potential as a novel target for molecular breeding to improve tomato tolerance to these stresses.