Genomic analysis of phospholipase D family and characterization of GmPLDαs in soybean (Glycine max)

Phospholipase D (PLD) and its product phosphatidic acid play important roles in the regulation of plant growth, development, and stress responses. The genome database analysis has revealed PLD family in Arabidopsis, rice, poplar and grape. In this study, we report a genomic analysis of 18 putative soybean (Glycine max) PLD genes (GmPLDs), which exist in the 14 of 20 chromosomes. GmPLDs were grouped into six types, alpha(3), beta(4), gamma, delta(5), epsilon(2), and zeta(3), based on gene architectures, protein domains, evolutionary relationship, and sequence identity. These GmPLDs contained two HKD domains, PX/PH domains (for GmPLD zeta s), and C2 domain (for the other GmPLDs). The expression patterns analyzed by quantitative reverse transcription PCR demonstrated that GmPLDs were expressed differentially in various tissues. GmPLD alpha 1, alpha 2, and beta 2 were highly expressed in most tissues, whereas GmPLD delta 5 was only expressed in flowers and GmPLD zeta 1 was predominantly expressed in flowers and early pods. The expression of GmPLD alpha 1 and alpha 2 was increased and that of GmPLD gamma was decreased by salt stress. GmPLD alpha 1 protein expressed in E. coli was active under the reaction conditions for both PLD alpha and PLD delta, hydrolyzing the common membrane phospholipids phosphatidylcholine, phosphatidylethanolamine, and phosphatidylglycerol. The genomic analysis for soybean PLD family provides valuable data for further identity and characterization of their functions.