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 A₂ (sPLA₂) provides lysophospholipid (LPL) from dietary phospholipids (PLs). We identified a sPLA₂, Se‐sPLA₂, in beet armyworm, Spodoptera exigua, that hydrolyses PLs at sn‐2. Our goal was to investigate its role in lipid digestion. Se‐sPLA₂ was expressed in the entire alimentary canal. Incubating the isolated midgut in a cell culture medium led to secretion of Se‐sPLA₂ and other proteins. Ex vivo RNA interference (RNAi) of Se‐sPLA₂ expression in isolated midgut culture led to significantly decreased Se‐sPLA₂ secretion into the medium. Feeding double‐stranded RNA specific to Se‐sPLA₂ to larvae suppressed sPLA₂ activity in gut contents. A recombinant Se‐sPLA₂ was susceptible to benzylideneacetone (BZA), a specific PLA₂ inhibitor. After feeding BZA to larvae, we recorded significant decreases in gut content sPLA₂ activity, body growth and total haemolymph lipid contents. RNAi against Se‐sPLA₂ 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‐sPLA₂ secreted from the midgut acts in lipid digestion by providing necessary LPL to solubilize dietary neutral lipids.

中文翻译：

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分泌型磷脂酶A2向斜纹夜蛾幼虫中肠管腔的分泌及其在脂质消化中的作用。

在昆虫中，脂质的消化是有争议的，因为昆虫没有胆盐可溶解饮食中的脂质。一种假设是分泌型磷脂酶A ₂（sPLA ₂）从膳食磷脂（PLs）提供溶血磷脂（LPL）。我们确定了的sPLA ₂，SE-的sPLA ₂，在甜菜夜蛾，甜菜夜蛾，，在水解的PL SN-2 。我们的目标是研究其在脂质消化中的作用。Se-sPLA ₂在整个消化道中表达。在细胞培养基中孵育分离的中肠可导致Se-sPLA ₂和其他蛋白质的分泌。的离体RNA干扰（RNAi）在分离的中肠培养物中Se-sPLA _2的表达导致培养基中Se-sPLA _2的分泌显着减少。将特定于Se-sPLA ₂的双链RNA喂入幼虫会抑制肠道内容物中sPLA _2的活性。重组Se-sPLA ₂对一种特定的PLA ₂抑制剂亚苄基丙酮（BZA）敏感。将BZA喂入幼虫后，我们发现肠道内容物sPLA ₂活性，身体生长和总血淋巴脂质含量显着下降。抗Se‐sPLA _2的RNAi导致消化率降低。添加特定的LPL 1-棕榈酰基-sn甘油3-磷酸胆碱对BZA处理的幼虫具有良好的消化率和幼体生长。这些结果有力地支持了我们的假设，即中肠分泌的Se-sPLA ₂通过提供必需的LPL来溶解饮食中性脂质来参与脂质消化。