A Global Analysis of the Polygalacturonase Gene Family in Soybean (<i>Glycine max</i>)

<div><p>Polygalacturonase is one of the pectin hydrolytic enzymes involved in various developmental and physiological processes such as seed germination, organ abscission, pod and anther dehiscence, and xylem cell formation. To date, no systematic analysis of polygalacturonase incorporating genome organization, gene structure, and expression profiling has been conducted in soybean (<i>Glycine max</i> var. Williams 82). In this study, we identified 112 <i>GmPG</i> genes from the soybean Wm82.a2v1 genome. These genes were classified into three groups, group I (105 genes), group II (5 genes), and group III (2 genes). Fifty-four pairs of duplicate paralogous genes were preferentially identified from duplicated regions of the soybean genome, which implied that long segmental duplications significantly contributed to the expansion of the <i>GmPG</i> gene family. Moreover, <i>GmPG</i> transcripts were analyzed in various tissues using RNA-seq data. The results showed the differential expression of 64 <i>GmPGs</i> in the tissue and partially redundant expression of some duplicate genes, while others showed functional diversity. These findings suggested that the <i>GmPGs</i> were retained by substantial subfunctionalization during the soybean evolutionary processes. Finally, evolutionary analysis based on single nucleotide polymorphisms (SNPs) in wild and cultivated soybeans revealed that 107 <i>GmPGs</i> had selected site(s), which indicated that these genes may have undergone strong selection during soybean domestication. Among them, one non-synonymous SNP of <i>GmPG031</i> affected floral development during selection, which was consistent with the results of RNA-seq and evolutionary analyses. Thus, our results contribute to the functional characterization of <i>GmPG</i> genes in soybean.</p>