Exploring Evolutionary Pathways and Abiotic Stress Responses through Genome-Wide Identification and Analysis of the Alternative Oxidase (AOX) Gene Family in Common Oat (Avena sativa)

The alternative oxidase (AOX), a common terminal oxidase in the electron transfer chain (ETC) of plants, plays a crucial role in stress resilience and plant growth and development. Oat (<i>Avena sativa</i>), an important crop with high nutritional value, has not been comprehensively studied regarding the AsAOX gene family. Therefore, this study explored the responses and potential functions of the AsAOX gene family to various abiotic stresses and their potential evolutionary pathways. Additionally, we conducted a genome-wide analysis to explore the evolutionary conservation and divergence of AOX gene families among three <i>Avena</i> species (<i>Avena sativa</i>, <i>Avena insularis</i>, <i>Avena longiglumis</i>) and four <i>Poaceae</i> species (<i>Avena sativa</i>, <i>Oryza sativa</i>, <i>Triticum aestivum</i>, and <i>Brachypodium distachyon</i>). We identified 12 AsAOX, 9 AiAOX, and 4 AlAOX gene family members. Phylogenetic, motif, domain, gene structure, and selective pressure analyses revealed that most AsAOXs, AiAOXs, and AlAOXs are evolutionarily conserved. We also identified 16 AsAOX segmental duplication pairs, suggesting that segmental duplication may have contributed to the expansion of the AsAOX gene family, potentially preserving these genes through subfunctionalization. Chromosome polyploidization, gene structural variations, and gene fragment recombination likely contributed to the evolution and expansion of the AsAOX gene family as well. Additionally, we hypothesize that <i>AsAOX2</i> may have potential function in resisting wounding and heat stresses, while <i>AsAOX4</i> could be specifically involved in mitigating wounding stress. <i>AsAOX11</i> might contribute to resistance against chromium and waterlogging stresses. <i>AsAOX8</i> may have potential fuction in mitigating ABA-mediated stress. <i>AsAOX12</i> and <i>AsAOX5</i> are most likely to have potential function in mitigating salt and drought stresses, respectively. This study elucidates the potential evolutionary pathways of the AsAOXs gene family, explores their responses and potential functions to various abiotic stresses, identifies potential candidate genes for future functional studies, and facilitates molecular breeding applications in <i>A. sativa</i>.