Department of Plant Medicals, Andong National University, Andong 36729, Republic of Korea.
Metabolomics Research Center for Functional Materials, Kyungsung University, Busan 48434, Republic of Korea.
Gen Comp Endocrinol. 2021 Jan 15;301:113659. doi: 10.1016/j.ygcen.2020.113659. Epub 2020 Nov 7.
Prostaglandins (PGs) mediate physiological processes of insects as well as mammals. Prostaglandin I (PGI) is a relatively well-known eicosanoid with potent hormone-like actions on various tissues of vertebrates, however, its presence and biosynthetic pathway have not been described in insects. This study demonstrated that fat bodies of the lepidopteran species, Spodoptera exigua, contained ~ 3.6 pg/g PGI. To identify its biosynthetic pathway, a PGI synthase gene of S. exigua (Se-PGIS) was predicted from a transcriptome of S. exigua; 25.6% homology with human PGIS was demonstrated. Furthermore, a predicted three-dimensional structure of Se-PGIS was demonstrated to be 38.3% similar to the human PGIS ortholog, including catalytic residues. Se-PGIS was expressed in all developmental stages of S. exigua and most abundant larval and adult stages; immune challenging of larvae significantly up-regulated these expression levels. The inducible expression of Se-PGIS expression was followed by a greater than four-fold increase in the concentration of PGI in fat bodies 10 h after immune challenge. RNA interference (RNAi) against Se-PGIS was performed by injecting double-stranded RNA (dsRNA). Under these RNAi conditions, cellular immune responses (e.g., hemocyte-spreading behavior, nodulation, phenoloxidase activity) were not affected by bacterial challenge. The addition of PGI to larvae treated with an eicosanoid biosynthesis inhibitor did not rescue the immunosuppression. Interestingly, PGI injection significantly suppressed nodule formation in response to bacterial challenge. In addition to the negative effect of PGI against immunity, the Se-PGIS-RNAi treatment significantly interfered with immature development and severely impaired oocyte development in female adults; the addition of PGI to RNAi-treated females significantly recovered oocyte development. Se-PGIS RNAi treatment also impaired male fertility by reducing fecundity after mating with untreated females. These results suggest that PGI acts as a negative regulator of immune responses initiated by other factors and mediates S. exigua development and reproduction.
前列腺素（PGs）介导昆虫和哺乳动物的生理过程。前列腺素 I（PGI）是一种相对知名的类二十烷酸，对脊椎动物的各种组织具有强烈的激素样作用，但其在昆虫中的存在和生物合成途径尚未描述。本研究表明，鳞翅目昆虫，斜纹夜蛾，脂肪体中含有约 3.6pg/g 的 PGI。为了鉴定其生物合成途径，从斜纹夜蛾转录组中预测了斜纹夜蛾的 PGI 合酶基因（Se-PGIS）；与人类 PGIS 具有 25.6%的同源性。此外，还证明了预测的 Se-PGIS 三维结构与人类 PGIS 同源物具有 38.3%的相似性，包括催化残基。Se-PGIS 在斜纹夜蛾的所有发育阶段都有表达，在幼虫和成虫阶段最为丰富；幼虫的免疫挑战显著上调了这些表达水平。免疫挑战 10 小时后，脂肪体中 PGI 的浓度增加了四倍以上，诱导了 Se-PGIS 的表达。通过注射双链 RNA（dsRNA）对 Se-PGIS 进行 RNA 干扰（RNAi）。在这些 RNAi 条件下，细胞免疫反应（例如，血细胞扩散行为、结节形成、酚氧化酶活性）不受细菌挑战的影响。在使用类二十烷酸生物合成抑制剂处理的幼虫中添加 PGI 不能挽救免疫抑制。有趣的是，PGI 注射显著抑制了对细菌挑战的结节形成。除了 PGI 对免疫的负面影响外，Se-PGIS-RNAi 处理还严重干扰了雌性成虫的不成熟发育和卵母细胞发育，并添加 PGI 可显著恢复 RNAi 处理的雌性卵母细胞发育。Se-PGIS RNAi 处理还通过降低与未处理雌性交配后的繁殖力来损害雄性的生育能力。这些结果表明，PGI 作为其他因素引发的免疫反应的负调节剂，介导斜纹夜蛾的发育和繁殖。
