Genome-wide identification and abiotic stress response analysis of the oat bHLH gene family

Basic helix-loop-helix (bHLH) transcription factors constitute a major gene family that governs plant development and abiotic stress responses. However, no comprehensive study of this family has been reported in hexaploid oat (Avena sativa L.).

We performed genome-wide identification and characterization of the bHLH family in oat, and delineated 271 AsbHLH genes unevenly distributed across the genome. Phylogenetic and evolutionary analyses were conducted, followed by expression profiling under salt, drought, gibberellin, methyl jasmonate, and salicylic acid treatments. Functional validation was carried out using an Arabidopsis bhlh257 mutant, an ortholog of a differentially expressed oat gene.

Phylogenetic and evolutionary analyses revealed a conserved subfamily structure alongside lineage-specific features, with segmental duplication identified as the primary driver of family expansion. Expression profiling identified a subset of core candidates, including AsbHLH110, AsbHLH121, AsbHLH204, and AsbHLH257, that were co-responsive to all tested stresses and hormones. Notably, AsbHLH257 demonstrated a 12.9-fold induction under drought stress (p< 0.0001). Functional validation using the Arabidopsis bhlh257 mutant confirmed the conserved role of bHLH transcription factors in drought tolerance and linked them to the regulation of oxidative stress homeostasis.

The co-responsive pattern supports the potential role of these candidates as integrative nodes in stress-hormone signaling networks. Collectively, this work establishes a prioritized candidate gene resource with crucial functional insights, providing a foundation for targeted genetic improvement of stress resilience in oat.