Work

Habitat-Adapted Fungal Symbionts Promote Salt Stress Tolerance Through Distinct Root Mechanisms and Shared Shoot Regulatory Networks in Arabidopsis thaliana

Year: 2026

Type: article

Abstract: Salinity is a major constraint to crop productivity. Beneficial plant–fungus interactions represent a promising strategy to enhance stress resilience. Here, we investigated fungal endophytes isolated from Oryza sativa cultivated in saline-prone marshlands of the Guadalquivir River, Spain. From a collection of 38 isolates, five salt-tolerant strains exhibiting plant growth-promoting activity were identified, including a previously uncharacterized Reticulascus sp. strain S5. Co-cultivation assays with Arabidopsis thaliana demonstrated that S5 increased root and shoot biomass under salt stress. To elucidate the underlying mechanisms, a comprehensive RNA-seq analysis of roots and shoots under control and saline conditions was performed. Fungal colonization induced pronounced transcriptomic changes, particularly in shoots, including the rewiring of auxin- and abscisic acid-related pathways and the induction of genes associated with cell wall remodelling. Concurrently, defence-related processes, including glucosinolate biosynthesis and ethylene signalling, were broadly repressed, suggesting attenuated stress perception in colonized plants. In roots, S5 infection suppressed genes involved in root hair development and cell wall organization, indicating a fungus-driven reconfiguration of root development. Comparative analysis with the growth-promoting Fusarium sp. K-23 revealed distinct root-associated mechanisms but convergence on a shared regulatory module in shoots involving ABA-responsive transcription factors and osmotic stress regulators. Collectively, our findings demonstrate that Reticulascus sp. S5 enhances plant salt stress tolerance through coordinated transcriptional reprogramming of growth, hormone signalling, and stress responses, highlighting the potential of habitat-adapted endophytes for sustainable crop improvement.

Source: International Journal of Molecular Sciences

DOI: 10.3390/ijms27177590