Plant growth-promoting functions of endophytic Fusarium annulatum alleviate the damage caused by saline stress in rice

Abstract

Fa-Os-1 regulates salt tolerance of rice by regulating physiological shape and genes expression in metabolism and secondary metabolites biosynthesis, revealing a growth-promoting mechanism of endophytic Fa-Os-1. Salt stress is an important constraining factor endangering crop yield and quality. Microorganisms have significant growth-promoting and stress resistance-enhancing effects on crops, but the mechanism by which microorganisms exert their growth-promoting effects under salt stress remains largely unexplained. This study isolated an endophytic fungus with significant salt tolerance from rice roots and focused on its regulatory effects on crop growth. Internal transcribed spacer (ITS) sequencing identified the fungus as Fusarium annulatum from Oryza sativa 1# (Fa-Os-1), a non-pathogenic species with a genome rich in growth-related and stress-relieving genes, with variations in genes associated with deoxynivalenol (DON) and zearalenone (ZEA) biosynthesis. Under salt stress, rice growth was enhanced following inoculation with Fa-Os-1 compared with the growth of untreated rice, which was attributed to enhanced antioxidant enzyme activity and nutrient uptake, reduced reactive oxygen species (ROS) levels in the plant, and significant changes in the expression of key genes involved in metabolism, secondary metabolite biosynthesis, phenylpropanoid biosynthesis, and plant hormone signal transduction. These differentially expressed genes were significantly enriched in biological processes, such as iron ion binding, oxidoreductase activity, hydrolase activity, and biosynthetic pathways of secondary metabolites. These results provide evidence of possible interaction mechanisms between endophytic fungi and crops under salt stress, and offer a theoretical basis to develop novel microbial fertilizers to mitigate the adverse effects of salt stress on crop growth.

Keywords: Fusarium annulatum; Endophytic fungi; Physicochemical properties; Rice; Transcriptome sequencing.