The strigolactones-mediated DNA demethylation activates the phosphoinositide pathway in response to salt stress

Abstract

Salt stress severely affects the growth and development of tomato. Strigolactones (SLs) and DNA methylation have been shown to be involved in the growth and development and response to salt stress in tomato. However, the regulation of SLs on DNA methylation in tomato under salt stress remains unclear. In this study, the interaction between SLs and DNA methylation inhibitors 5-azacytidine (5-azaC) alleviate salt stress damage by increasing the plant height, stem diameter, leaf area, and root length of tomato, as well as enhancing the biosynthesis of chlorophyll, carotenoid and flavonoid. The transcriptome and genome-wide methylation analysis between NaCl and NaCl + GR24 treatment show that plant-pathogen interaction, MAPK signaling pathway, plant hormone signal transduction and phosphatidylinositol signaling system may be means for SLs in response to salt stress. Among, SLs strikingly up-regulate the pivotal genes related to phosphatidylinositol signaling system, and reduce CHG methylation level in promoter and body region of these genes under salt stress, implying that SLs mediated-demethylation may promote gene expression. The determination results of relevant metabolites and gene expression levels in the phosphatidylinositol signaling system suggest that PIP₂, DAG, IP₃, and PA are raised by co-treatment of SLs and 5-azaC under salt stress relative to NaCl + 5-azaC treatment. The same response pattern is also presented in the SlPLC2, SlNPC1, SlPLD-Z, SlPLD-B, SlDGK1, SlDGK5, SlDGK7 and SlPIP5K9 genes. These results strongly indicate that phosphatidylinositol signaling system response to salt stress is related to the SLs mediated-demethylation, and provide a potential means for defenses salt stress in tomato.

Keywords: DNA methylation; Gene expression; Phosphatidylinositol; Salt stress; Strigolactones.