Genome-wide analysis of calcium-dependent protein kinases and their expression patterns in response to herbivore and wounding stresses in soybean

Calcium-dependent protein kinases (CDPKs) play important roles in various aspects of plant physiology and involve in many cellular processes. However, genome-wide analysis of CDPK family in plant species is limited and few studies have been reported in soybean. In this study, a total of 39 genes encoding CDPKs were identified from the whole-genome sequence of soybean (Glycine max), which were denominated as GmCPK1-GmCPK39. These 39 CDPK genes could be classified into four subfamilies, and most genes showed tissue-specific expression patterns. Eight soybean CDPKs clustered together with the previously reported CDPKs related to pathogen, wounding, or herbivore stress were further analyzed. Differential gene expression analysis of these eight CDPK genes in response to herbivore and wounding stresses helps us identify GmCPK3 and GmCPK31 as the candidate genes for herbivore resistance in soybean, whose relative transcript abundance rapidly increased after wound and herbivore attacks. Sub-cellular localization revealed that GmCPK3 and GmCPK31 were localized in plasma membranes, which is consistent with previously reported plant defense related CDPKs. These results may suggest that GmCPK3 and GmCPK31 play important roles in the plant response to biotic stress. Simultaneously, our study will provide an important foundation for further functional characterization of the soybean CDPK gene family.