Genome-wide unraveling of the AUX/IAA family in Avena sativa L. with observations on seedling root growth and stress resilience

The Aux/IAA gene family plays a central role in auxin signaling and plant development. To investigate the underlying molecular mechanisms, we performed a genome-wide identification of the Aux/IAA gene family in Avena sativa . In this study, we observed that exogenous IAA exerts a dual regulatory effect on A. sativa root growth—promoting elongation at low concentrations (5–50 µM) and inhibiting it at high concentrations (100–200 µM)— highlighting the dose-dependent nature of auxin action. To investigate the underlying molecular mechanisms, we performed a genome-wide identification of the Aux/IAA gene family in Avena sativa . A total of 40 AsIAA genes were identified and phylogenetically classified into five subfamilies. Structural and motif analyses confirmed evolutionary conservation, while duplication analysis revealed that segmental and tandem events contributed to family expansion. Expression profiling showed tissue-specific patterns, with AsIAA13/15/19 preferentially expressed in flowers and AsIAA17 enriched in leaves. Under IAA, PEG, NaCl, and temperature treatments, six selected AsIAA genes ( AsIAA6/11/13/15/17/19 ) exhibited distinct and stress-specific expression changes, suggesting their potential involvement in both developmental regulation and environmental adaptation. These findings suggest their potential involvement in both developmental regulation and environmental adaptation. This study provides a comprehensive characterization of the AsIAA gene family and offers candidate genes for functional studies and molecular breeding in A. sativa .