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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >The phytohormone precursor OPDA is isomerized in the insect gut by a single, specific glutathione transferase
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The phytohormone precursor OPDA is isomerized in the insect gut by a single, specific glutathione transferase

机译:植物激素前体OPDA在昆虫肠道中通过单一特异性谷胱甘肽转移酶异构化

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摘要

Oxylipins play important roles in stress signaling in plants. The compound 12-oxophytodienoic acid (cis-OPDA) is an early biosyn-thetic precursor of jasmonic acid (JA), the key phytohormone orchestrating the plant anti-herbivore defense. When consumed by feeding Lepidopteran larvae, plant-derived cis-OPDA suffers rapid isomeriza-tion to iso-OPDA in the midgut and is excreted in the frass. Unlike OPDA epimerization (yielding trans-OPDA), the formation of iso-OPDA is enzyme-dependent, and is catalyzed by an inducible glutathione transferase (GSTs) from the larval gut. Purified GST fractions from the gut of Egyptian cotton leafworm (Spodoptera littoralis) and cotton boll worm (Helicoverpa armigera) both exhibited strong OPDA isomerization activity, most likely via transient formation of a gluta-thione-OPDA conjugate. Out of 16 cytosolic GST proteins cloned from the gut of cotton bollworm larvae and expressed in E. coli, only one catalyzed the OPDA isomerization. The biological function of the double bond shift might be seen in an inactivation of cis-OPDA, similar to the inactivation of prostaglandin A1 to prostaglandin B1 in mammalian tissue. The enzymatic isomerization is particularly widespread among generalist herbivores that have to cope with various amounts of cis-OPDA in their spectrum of host plants.
机译:脂磷脂在植物的胁迫信号传导中起重要作用。化合物12-氧代乙二酸(cis-OPDA)是茉莉酸(JA)的早期生物合成前体,茉莉酸是构成植物抗草食动物防御能力的关键植物激素。当通过喂食鳞翅目幼虫而被消耗时,植物来源的顺式-OPDA在中肠中会迅速异构化为iso-OPDA,并排泄到怪胎中。与OPDA差向异构化(产生反式OPDA)不同,iso-OPDA的形成是酶依赖性的,并且是由幼虫肠道中的诱导型谷胱甘肽转移酶(GST)催化的。来自埃及棉叶虫(Spodoptera littoralis)和棉铃虫(Helicoverpa armigera)肠道的纯化GST馏分均具有很强的OPDA异构化活性,很可能是通过瞬时形成谷氨硫酮-OPDA共轭物而形成的。从棉铃虫幼虫的肠道克隆并在大肠杆菌中表达的16种胞质GST蛋白中,只有一种催化OPDA异构化。双键转移的生物学功能可能在顺式OPDA失活中看到,类似于哺乳动物组织中前列腺素A1到前列腺素B1的失活。酶促异构化在通才草食动物中特别普遍,这些食草动物在其寄主植物的光谱中必须应对各种量的顺式-OPDA。

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