Department of Plant and Environmental Sciences, Pee Dee Research and Education Center, Clemson University, Florence, SC 29506, USA.
Department of Crop and Soil Sciences, Washington State University, Pullman, WA 99164, USA.
Int J Mol Sci. 2019 Jun 23;20(12):3064. doi: 10.3390/ijms20123064.
The channeling of metabolites is an essential step of metabolic regulation in all living organisms. Multifunctional enzymes with defined domains for metabolite compartmentalization are rare, but in many cases, larger assemblies forming multimeric protein complexes operate in defined metabolic shunts. In , a multimeric complex was discovered that contains a 13-lipoxygenase and allene oxide synthase (AOS) as well as allene oxide cyclase. All three plant enzymes are localized in chloroplasts, contributing to the biosynthesis of jasmonic acid (JA). JA and its derivatives act as ubiquitous plant defense regulators in responses to both biotic and abiotic stresses. AOS belongs to the superfamily of cytochrome P450 enzymes and is named CYP74A. Another CYP450 in chloroplasts, hydroperoxide lyase (HPL, CYP74B), competes with AOS for the common substrate. The products of the HPL reaction are green leaf volatiles that are involved in the deterrence of insect pests. Both enzymes represent non-canonical CYP450 family members, as they do not depend on O and NADPH-dependent CYP450 reductase activities. AOS and HPL activities are crucial for plants to respond to different biotic foes. In this mini-review, we aim to summarize how plants make use of the LOX2-AOS-AOC2 complex in chloroplasts to boost JA biosynthesis over volatile production and how this situation may change in plant communities during mass ingestion by insect pests.
代谢物的定向输送是所有生物体进行代谢调控的一个基本步骤。具有明确代谢物分隔结构域的多功能酶很少见，但在许多情况下，形成多聚体蛋白复合物的更大组装体在特定的代谢分路中发挥作用。在 ，发现了一个包含 13-脂氧合酶、丙二烯氧化物合酶（AOS）和丙二烯氧化物环化酶的多聚体复合物。这三种植物酶都定位于叶绿体中，有助于茉莉酸（JA）的生物合成。JA 和其衍生物作为普遍存在的植物防御调节剂，在应对生物和非生物胁迫时发挥作用。AOS 属于细胞色素 P450 酶的超家族，被命名为 CYP74A。另一种在叶绿体中的细胞色素 P450 酶，过氧化物水解酶（HPL，CYP74B），与 AOS 竞争共同的底物。HPL 反应的产物是绿叶挥发物，参与对害虫的威慑。这两种酶都代表非典型的 CYP450 家族成员，因为它们不依赖于 O 和 NADPH 依赖的 CYP450 还原酶活性。AOS 和 HPL 的活性对植物应对不同的生物敌人至关重要。在这篇迷你综述中，我们旨在总结植物如何利用叶绿体中的 LOX2-AOS-AOC2 复合物来促进 JA 生物合成，而不是促进挥发性物质的产生，以及在昆虫大量取食植物群落时，这种情况可能会如何改变。
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