Genome-Wide Identification and Comprehensive Analysis of the Gene Family in and .

Background: Polyphenol oxidases () form a multigene family that is widely distributed in plants, animals, and insects. To date, have been identified in plants such as L. and L., but studies on in soybean ( (L.) Merr.) and wild soybean ( Sieb. and Zucc.) remain limited.

Methods: To clarify the nature, structure, evolution, expression pattern, and interaction network of in these plants, we performed bioinformatics analysis and evaluated the expression patterns of in soybean and wild soybean throughout the growth period and under salt stress.

Results: We identified 17 and 15 genes belonging to the PPO family. These genes were distributed across chromosomes 7 and 6 and could be divided into three groups. Most of these genes only contained one coding sequence (CDS), and their gene structure, conserved motifs, and 3D structures were very similar. Although there were a few intraspecies gene duplications, 75 gene replication pairs between soybean and wild soybean were detected. A Ka/Ks analysis showed that the in these plants were mainly subjected to purity selection. Moreover, the expression of the genes varied greatly during different stages of the growth period and under salt stress, showing high temporal and spatial specificity. The protein interaction networks of these genes appeared to be quite distinct. Through the interaction analysis of the candidate gene selected under salt stress, , , and were identified as the candidate genes regulating salt stress tolerance in soybean.

Conclusions: These findings provide a foundation for further research on the evolution of soybean and wild soybean, as well as the functions of the gene family.