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首页> 外文期刊>Journal of Experimental Botany >Differential distribution of the lipoxygenase pathway enzymes within potato chloroplasts
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Differential distribution of the lipoxygenase pathway enzymes within potato chloroplasts

机译：马铃薯叶绿体中脂氧合酶途径酶的差异分布

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The lipoxygenase pathway is responsible for the production of oxylipins, which are important compounds for plant defence responses. Jasmonic acid, the final product of the allene oxide synthase/allene oxide cyclase branch of the pathway, regulates wound-induced gene expression. In contrast, C6 aliphatic aldehydes produced via an alternative branch catalysed by hydroperoxide lyase, are themselves toxic to pests and pathogens. Current evidence on the subcellular localization of the lipoxygenase pathway is conflicting, and the regulation of metabolic channelling between the two branches of the pathway is largely unknown. It is shown here that while a 13-lipoxygenase (LOX H3), allene oxide synthase and allene oxide cyclase proteins accumulate upon wounding in potato, a second 13-lipoxygenase (LOX H1) and hydroperoxide lyase are present at constant levels in both non-wounded and wounded tissues. Wound-induced accumulation of the jasmonic acid biosynthetic enzymes may thus commit the lipoxygenase pathway to jasmonic acid production in damaged plants. It is shown that all enzymes of the lipoxygenase pathway differentially localize within chloroplasts, and are largely found associated to thylakoid membranes. This differential localization is consistently observed using confocal microscopy of GFP-tagged proteins, chloroplast fractionation, and western blotting, and immunodetection by electron microscopy. While LOX H1 and LOX H3 are localized both in stroma and thylakoids, both allene oxide synthase and hydroperoxide lyase protein localize almost exclusively to thylakoids and are strongly bound to membranes. Allene oxide cyclase is weakly associated with the thylakoid membrane and is also detected in the stroma. Moreover, allene oxide synthase and hydroperoxide lyase are differentially distributed in thylakoids, with hydroperoxide lyase localized almost exclusively to the stromal part, thus closely resembling the localization pattern of LOX H1. It is suggested that, in addition to their differential expression pattern, this segregation underlies the regulation of metabolic fluxes through the alternative branches of the lipoxygenase pathway.
机译：脂氧合酶途径负责产生氧脂素，其是植物防御反应的重要化合物。茉莉酸是该途径的氧化烯合酶/氧化烯环化酶分支的最终产物，调节伤口诱导的基因表达。相反，通过氢过氧化物裂解酶催化的另一分支产生的C6脂族醛本身对害虫和病原体有毒。关于脂氧合酶途径的亚细胞定位的当前证据是矛盾的，并且该途径的两个分支之间的代谢通道的调节在很大程度上是未知的。结果表明，马铃薯中的13-脂氧合酶（LOX H3），氧化烯合酶和氧化烯环化酶蛋白在伤口上积累时，第二种13-脂氧合酶（LOX H1）和氢过氧化物裂解酶在非马铃薯中均以恒定水平存在。受伤的组织。伤口引起的茉莉酸生物合成酶的积累可能因此使脂氧合酶途径参与受损植物中茉莉酸的产生。结果表明，脂氧合酶途径的所有酶在叶绿体中差异定位，并且很大程度上与类囊体膜有关。使用GFP标记的蛋白质的共聚焦显微镜，叶绿体分级分离和Western印迹，以及通过电子显微镜进行的免疫检测，可以始终观察到这种差异化定位。虽然LOX H1和LOX H3既位于基质，也位于类囊体中，但氧化烯合酶和氢过氧化物裂解酶蛋白几乎都位于类囊体中，并牢固地结合在膜上。烯丙氧化物环化酶与类囊体膜弱相关，在基质中也可检测到。此外，氧化烯合酶和氢过氧化物裂解酶在类囊体中差异分布，氢过氧化物裂解酶几乎仅定位于基质部分，因此与LOX H1的定位模式非常相似。提示，除了它们的差异表达模式外，这种分离还通过脂氧合酶途径的可替代分支来调节代谢通量。

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