Fusarium sp. Strain K-23 Alleviates Salt Stress in Arabidopsis thaliana Through its Root Hair Growth-Promoting Effect

Abstract

Soil salinity is a significant abiotic stress factor that impedes plant growth and crop yield, particularly in arid and semi-arid regions. Recent reports indicate that 8.7% of soils globally and 20–50% of irrigated soils across all continents are affected by salt. This phenomenon jeopardizes the food security of more than 1.5 billion people worldwide. Numerous studies have elucidated the beneficial effects of diverse microbes on plant abiotic stress tolerance. In this study, we report on an observed molecular mechanism involved in the enhanced salt tolerance of Arabidopsis plants co-cultivated with the Fusarium sp. strain K-23. Employing a combination of transcriptomics, phenomics, reverse genetics, and live cell imaging, we elucidated the intricacies of biological processes that influence root growth in the interaction between A. thaliana and the fungus. Moreover, our research corroborated the beneficial effect of the fungus under salt-stress conditions for Arabidopsis and highlighted notable differences compared to previous studies. We utilized an RNA-seq approach to identify biological processes triggered in Arabidopsis roots that interact with K-23, resulting in increased salt tolerance. These experiments necessitated a more comprehensive investigation into the fungal influence on root hair development and elucidated that induced root hair growth was a prerequisite for the enhanced salt stress tolerance conferred by the fungus. Furthermore, we demonstrate that the fungus induces the expression of the NAC transcription factor JUNGBRUNNEN 1 (JUB1). Elevated expression of JUB1 leads to repression of gibberellin biosynthesis, which, in turn, contributes to sustained root hair growth under salt stress conditions, which typically suppresses root hair growth substantially.