Evolutionary and functional insights into ascorbate oxidase genes in the Fabaceae plant family

Abstract

Ascorbate oxidase (AAO), a multicopper oxidase protein, plays a crucial role in catalyzing the oxidation of ascorbic acid (AA) in the apoplastic space. Despite the extensive attention on AAO functions, a significant gap remains in understanding its evolutionary trajectory and functional intricacies within the Fabaceae family that is recognized for its nutritional and economic importance. Our investigation revealed substantial conservation of the AAO gene family across all 21 studied Fabaceae species. Phylogenetic analysis consistently clustered Fabaceae AAO genes into two well-supported groups, indicating their shared and conserved origin. Similarly, gene structure analyses categorized sequences into two groups based on intronic sizes. Furthermore, motif analysis revealed ten conserved motifs in almost all of the AAO sequences. Notably, chromosomal localization data for Glycine max and Glycine soja AAO genes exhibited a highly similar gene distribution across the genome. Through comprehensive cis-regulatory analysis of G. max AAO genes, we identified binding motifs for transcription factors associated with various biological functions, including development, growth, and responses to biotic and abiotic stresses. Additionally, gene expression analyses unveiled significant variability in AAO gene expression profiles under different environmental stressors, highlighting the dynamic functional role of AAO in response to biotic and abiotic stresses. Our findings facilitated the identification of multiple AAO homologs in Fabaceae species, thereby enhancing our understanding of the functional roles of this gene family.