Insights on the impact of arbuscular mycorrhizal symbiosis on Avena sativa drought tolerance at the early flowering stage

Oats ( Avena sativa ) are a nutritious and versatile crop, but they are highly vulnerable to drought, especially during the heading and flowering stages, which significantly reduce yield and quality. Arbuscular mycorrhizal fungi (AMF) can improve plant resilience to drought and other abiotic stresses. However, the genetic networks underlying oat responses to drought during the early flowering stage, influenced by AMF, remain unclear. In this study, we used transcriptome sequencing, phenotypic, and physiological analyses to investigate how AMF enhance drought tolerance in oats. Samples were collected on day 60 of oat-AMF symbiosis (corresponding to day 30 of drought stress), with the 30-day drought period covering the critical water-sensitive phase of panicle initiation to flowering in oats. We found that AMF inoculation enhanced multiple drought-related traits in oats, including growth parameters, root vitality, antioxidant enzyme activity, and levels of oxidative glutathione (GSSG), indole-3-acetic acid (IAA), and abscisic acid (ABA). Transcriptomic analysis further identified differentially expressed genes involved in drought response, membrane integrity, and transport activities, with a focus on genes associated with stress tolerance. KEGG pathway analysis revealed phenylpropanoid biosynthesis and plant hormone signal transduction were significantly affected under drought and AMF inoculation. Further analysis showed that genes such as PAL , PYL5 , CRE1 , and B-ARR were differentially expressed in AMF-inoculated oat roots under drought stress. Additionally, weighted gene co-expression network analysis identified hub genes related to plant growth and defense ( BGLU16, CGS1 ), oxidative stress ( CAT2, RBOH ), and phosphate and nutrient transport ( PHF1, PHT1-11, PIPs, YSL13 ). Overall, these results provide valuable insights into the complex genetic networks underlying AMF-enhanced drought resilience in at oats early flowering stage, offering potential candidate genes for future studies aimed at improving drought tolerance through mycorrhizal-plant interactions. • Arbuscular mycorrhizal fungi (AMF) inoculation enhanced oat ( Avena sativa ) drought tolerance at the early flowering stage by improving root vitality, elevating GSH content, and increasing peroxidase activity, which enhanced antioxidant defense and led to higher biomass and yield under drought stress. • Transcriptomic analysis revealed that AMF regulated key drought-responsive genes in phenylpropanoid biosynthesis ( PAL ), hormone signaling ( PYL5, CYP707A3, CRE1, B-ARR, snRK2, IAA7 ), and osmotic regulation ( P5CS2 ), indicating a broad modulation of stress signaling pathways. • AMF symbiosis influenced water and nutrient transport by upregulating aquaporin genes ( PIP1;5, PIP2;2, PIP2;3 ) and phosphate transporters ( PHF1, PHT1-11 ), enhancing water uptake, phosphate acquisition, and resource-use efficiency under drought stress. • WGCNA identified AMF-induced hub genes related to growth ( MYBAS1, BGLU16 ), oxidative defense ( CAT2, RBOH ), and carbohydrate metabolism, demonstrating that AMF reprograms gene networks to strengthen antioxidant systems and drought adaptation in oats.