Premium
Secretion of secretory phospholipase A 2 into Spodoptera exigua larval midgut lumen and its role in lipid digestion
Author(s) -
Sajjadian S. M.,
Vatanparast M.,
Stanley D.,
Kim Y.
Publication year - 2019
Publication title -
insect molecular biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.955
H-Index - 93
eISSN - 1365-2583
pISSN - 0962-1075
DOI - 10.1111/imb.12588
Subject(s) - midgut , biology , digestion (alchemy) , lipid digestion , exigua , biochemistry , beet armyworm , secretion , spodoptera , phospholipase a2 , phospholipase , lipid droplet , hemolymph , phospholipase a , enzyme , larva , lipase , botany , recombinant dna , gene , chemistry , chromatography
In insects, lipid digestion is controversial because insects have no bile salts to solubilize dietary lipids. One hypothesis is that a secretory type of phospholipase A 2 (sPLA 2 ) provides lysophospholipid (LPL) from dietary phospholipids (PLs). We identified a sPLA 2 , Se‐sPLA 2 , in beet armyworm, Spodoptera exigua , that hydrolyses PLs at sn‐2 . Our goal was to investigate its role in lipid digestion. Se‐sPLA 2 was expressed in the entire alimentary canal. Incubating the isolated midgut in a cell culture medium led to secretion of Se‐sPLA 2 and other proteins. Ex vivo RNA interference (RNAi) of Se‐sPLA 2 expression in isolated midgut culture led to significantly decreased Se‐sPLA 2 secretion into the medium. Feeding double‐stranded RNA specific to Se‐sPLA 2 to larvae suppressed sPLA 2 activity in gut contents. A recombinant Se‐sPLA 2 was susceptible to benzylideneacetone (BZA), a specific PLA 2 inhibitor. After feeding BZA to larvae, we recorded significant decreases in gut content sPLA 2 activity, body growth and total haemolymph lipid contents. RNAi against Se‐sPLA 2 resulted in reduced digestibility. Addition of a specific LPL, 1‐palmitoyl‐ sn ‐glycero‐3‐phosphocholine, to BZA‐treated larvae rescued digestibility and larval growth. These results strongly bolster our hypothesis that Se‐sPLA 2 secreted from the midgut acts in lipid digestion by providing necessary LPL to solubilize dietary neutral lipids.