Mutant Identification Of Phospholipase D And Characterization Of PLDβ2 In Rice

Phospholipase D (PLD) hydrolyzes phospholipids to produce phosphatidic acid (PA), a signal messenger, resulting in membrane remodeling in cells. Studies in Arabidopsis show that the activation of PLD plays an important in various biological processes including plant growth, development and stress responses. However, the role of rice PLD remains unclear. The rice genome contains 17 PLD genes. To characterize their functions, the T-DNA insertion mutants of rice PLDs including PLDal, PLDa2, PLDa3, PLDa6, PLDβ1, PLDβ2, PLDδ2, PLDζ1 and PLDζ2 were isolated by PCR. The expression level PLD gene in individual mutant was tested by semi-quantitative RT-PCR. The PLDδ2 expression level in pldδ2 mutant was elevated resulting from the T-DNA inserted in the promoter region of the gene. The mRNA of PLDζ2 and PLDβ2 and PLDal were completely abolished in thepldζ2 and pldβ2 and pldal, respectively. The expression levels of 17 PLDs were profiled by semi-quantitive RT-PCR in response to salt stress. The most PLDs were induced by salt treatment for 12 h, suggesting PLD may be involved in salt response. Preliminary observations showed that PLDβ2 knockout mutant pldβ2 plants were more susceptible to salt stress with severer growth inhibition, less numbers of tillering and heading，as compared to wild type plants. The plant height and seed length of pldβ2 were less than that of WT under normal growth condition. The result suggests that PLDβ2 plays a role in growth regulation and salt response. In addition, PLDδ2 was cloned and the protein was expressed in BL121 cells, and protein of expected size was obtained for further analysis.