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 can 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 combined transcriptome sequencing with 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 oxidized 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 that 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-ARRs 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), phosphate and nutrient transport (PHF1, PHT1-11,YSL13), and water transport (PIPs). Overall, these results provide valuable insights into the complex genetic networks underlying AMF-enhanced drought resilience in oats at early flowering stage, offering potential candidate genes for future studies aimed at improving drought tolerance through mycorrhizal-plant interactions.