Max Planck Institute for Chemical Ecology, Jena, Germany.
FEBS J. 2014 Jun;281(12):2769-83. doi: 10.1111/febs.12819. Epub 2014 May 16.
12-Oxophytodienoic acid (OPDA), a well-known phytohormone of the jasmonate family, has a reactive α,β-unsaturated carbonyl structure which easily adds cellular nucleophiles (Michael addition), making OPDA potentially toxic for herbivores. The glutathione S-transferase GST16 inactivates 12-OPDA in the insect gut by isomerization to inactive iso-OPDA. Quantitative tissue expression analysis showed that HarmGST16 transcripts were present in most larval tissues, including those of the midgut, fatbody and Malpighian tubules. Activity assays confirmed the presence of an active enzyme. Interestingly, feeding different diets to Helicoverpa armigera influenced gst16 expression levels in various tissues, and larvae fed wild-type tobacco leaves had reduced gst16 mRNA levels. The temporal expression of HarmGST16 during larval development was high in the second instar and reduced during the third, fourth and fifth instars. Plant-mediated RNA interference silencing of HarmGST16 retarded larval growth of H. armigera. Injecting cis-OPDA into the hemolymph of larvae caused premature pupation. This result, as well as the finding that GST16 influenced the growth of insects, suggests that GST16 may play an important role in larval development.
12-氧代植二烯酸（OPDA），一种众所周知的茉莉酸家族植物激素，具有反应性的α，β-不饱和羰基结构，容易与细胞亲核试剂（迈克尔加成）加成，使 OPDA 对草食动物具有潜在毒性。谷胱甘肽 S-转移酶 GST16 通过异构化为无活性的 iso-OPDA 使 12-OPDA 在昆虫肠道中失活。定量组织表达分析表明，HarmGST16 转录本存在于大多数幼虫组织中，包括中肠、脂肪体和马氏管。活性测定证实了存在活性酶。有趣的是，不同饮食喂养的棉铃虫在不同组织中影响 gst16 的表达水平，并且喂食野生型烟草叶片的幼虫 gst16 mRNA 水平降低。HarmGST16 在幼虫发育过程中的时间表达在第二龄期很高，在第三、第四和第五龄期降低。通过植物介导的 HarmGST16 RNA 干扰沉默会延缓棉铃虫幼虫的生长。向幼虫的血淋巴中注射顺式 OPDA 会导致过早化蛹。这一结果以及 GST16 影响昆虫生长的发现表明，GST16 可能在幼虫发育中发挥重要作用。
