Molecular Characterization of Two Genes Encoding Novel Ca2+-Independent Phospholipase A2s from the Silkworm, Bombyx mori

Abstract

Eicosanoids are crucial downstream signals in the insect immune responses. Phospholipase A2 (PLA2) catalyzes phospholipids, the initial step in eicosanoid biosynthesis. In mammals, the biological roles of Ca2+-independent Phospholipase A2 (iPLA2) have been extensively studied; however, only a few studies have attempted to explore iPLA2 functions in insects. In this study, we identified two iPLA2 genes (designated as BmiPLA2A and BmiPLA2B) in the silkworm, Bombyx mori. BmiPLA2A had a 2427 base pair (bp) open reading frame (ORF) that coded for a protein with 808 amino acids. In contrast, BmiPLA2B had a 1731 bp ORF that coded for a protein with 576 amino acids. Domain analysis revealed that BmiPLA2A had six ankyrin repeat domains, but BmiPLA2B lacks these domains. BmiPLA2A and BmiPLA2B were transcribed widely in various tissues and developmental stages with different expression patterns. The administration of 20-hydroxyecdysone increased their expression levels in the epidermis and hemocytes. Furthermore, challenged with virus, fungus, Gram-negative bacteria, and Gram-positive bacteria induced the expression of BmiPLA2A and BmiPLA2B with variable degrees along with different time points. Our findings imply that BmiPLA2A and BmiPLA2B may have important biological roles in the development and innate immunity of B. mori.

Whole transcriptome sequencing reveals the activity of the PLA2 family members in Androctonus crassicauda (Scorpionida: Buthidae) venom gland

“…Previous studies have also documented that pathogen stimuli significantly affect iPLA2 family members' expression levels. 15,42 It has also been demonstrated that iPLA2 isoforms exhibit lipid hydrolase or transacylase/ acyltransferase activities. 23 The lack of F I G U R E 1 1 Phylogenetic tree of deduced amino acid sequences for PLA2 family members from A. crassicauda.…”

“…It has been stated that PLA2s play their roles by producing lipid mediators, altering membrane phospholipid composition, degrading foreign phospholipids, and modifying extracellular lipid components such as lipoproteins. [13][14][15][16] The catalytic activity of the PLA2s triggers a cascade of inflammatory events including release of a complex network of inflammatory mediators. 17,19 The existing literature demonstrates that the sPLA2 subfamily catalyzes the hydrolysis of the sn-2 fatty acid bond of phospholipids, releasing free fatty acids and lysophospholipids.…”

“…The PLA2s have a relevant role in the inflammatory process and inhibition of ryanodine receptor channels, which have neuronal activity 10–12 ; they also participate in membrane homeostasis. It has been stated that PLA2s play their roles by producing lipid mediators, altering membrane phospholipid composition, degrading foreign phospholipids, and modifying extracellular lipid components such as lipoproteins 13–16 …”

MicroRNAs reshape the immunity of insects in response to bacterial infection

“…It has been established that in order for the host to respond effectively to microbial pathogens, a number of cellular signals require to be finely modulated, including immune signaling (3,(96)(97)(98). As described above, miRNA expression is strongly altered in response to bacterial pathogens.…”

The Potential Biological Roles of Circular RNAs in the Immune Systems of Insects to Pathogen Invasion

“…There are significant medical and economic costs associated with viruses that infect insects. So far, a large number of studies and review articles have been published that address the insect innate immunity and the molecules associated with immunity that is involved in the anti-viral processes of insects [ 73 , 74 , 75 , 76 , 77 , 78 ]. However, the biological role of circRNAs in the regulation of innate immunity during viral infection is still unknown.…”