摘要

Phospholipase A(2) (PLA(2)) catalyzes hydrolysis of ester linlcage at sn-2 position of phospholipids. At least 15 groups (I-XV) of PLA(2) gene superfamily are associated with various physiological processes such as digestion, secretion, immunity, and maintenance of membrane integrity. This study suggests that various insects encode putative Group VI PLA(2)s representing intracellular and calcium-independent PLA(2)s (iPLA(2)). These insect iPLA(2)s are separated into at least two subgroups: iPLA(2)A (Group VIA-like) and iPLA(2)B (non-Group VIA). Most insects encode genes of iPLA(2)B type, although their biological functions are currently unknown. This study predicted a novel iPLA(2) from Spodoptera exigua (a lepidopteran insect) (SeiPLA(2)B) and analyzed its physiological functions by RNA interference (RNAi). SeiPLA(2)B encodes 336 amino acid sequence with a predicted size of about 36.6 kDa and an isoelectric point at pH 8.61. It possesses a lipase catalytic site, but does not have ankyrin repeats in the amino terminal region. Phylogenetic analysis indicated that SeiPLA(2)B was clustered with other Group VI iPLA(2)s, in which SeiPLA(2)B was closely associated with Group VIF gene while SeiPLA(2)A was closely related to Group VIA gene. SeiPLA(2)B was expressed in all developmental stages of S. exigua. In larval stage, SeiPLA(2)B was expressed in fat body, hemocyte, and epidermis, but not in digestive tract. SeiPLA(2)B RNAi significantly reduced PLA(2) enzyme activities and resulted in developmental retardation and immunosuppression. Though RNAi treatment did not significantly change fatty acid composition in fat body lipids, it significantly increased lipid peroxidation. Taken together, our results suggest that SeiPLA(2)B plays important roles in the development and immunity of S. exigua.

  • 出版日期2017-12