Differential distribution of the lipoxygenase pathway enzymes within potato chloroplasts
Differential distribution of the lipoxygenase pathway enzymes within potato chloroplasts
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DOI：
10.1093/jxb/erl230
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发表时间：
2007-02-01
影响因子：
6.9
通讯作者：
Sanchez-Serrano, Jose J.
中科院分区：
文献类型：
--
作者：
Farmaki, Theodora;Sanmartin, Maite;Sanchez-Serrano, Jose J.
脂氧合酶途径负责氧脂素的产生，氧脂素是植物防御反应的重要化合物。茉莉酸是丙二烯氧化物合成酶/丙二烯氧化物环化酶分支的最终产物，调节创伤诱导的基因表达。相比之下，通过氢过氧化物裂解酶催化的替代分支产生的C6脂族醛本身对害虫和病原体有毒。目前关于脂氧合酶途径的亚细胞定位的证据是相互矛盾的，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。它在这里显示，虽然13-脂氧合酶（LOX H3），丙二烯氧化物合酶和丙二烯氧化物环化酶蛋白质积累创伤后，在马铃薯，第二个13-脂氧合酶（LOX H1）和氢过氧化物裂解酶是目前在非受伤和受伤的组织在恒定的水平。因此，损伤诱导的茉莉酸生物合成酶的积累可能使受损植物中的茉莉酸生产通过脂氧合酶途径进行。结果表明，所有的脂氧合酶途径的酶差异定位在叶绿体内，并在很大程度上被发现与类囊体膜。这种差异定位始终观察到使用共聚焦显微镜的GFP标记的蛋白质，叶绿体分馏，和Western印迹，和免疫检测电子显微镜。虽然LOX H1和LOX H3都位于基质和类囊体中，但丙二烯氧化物合酶和氢过氧化物裂解酶蛋白几乎完全位于类囊体中，并与膜强烈结合。丙二烯氧化物环化酶与类囊体膜弱相关，也在基质中检测到。此外，丙二烯氧化物合酶和氢过氧化物裂解酶的差异分布在类囊体，氢过氧化物裂解酶几乎完全定位于基质的一部分，因此非常类似的本地化模式LOX H1。有人建议，除了他们的差异表达模式，这种分离的基础上的脂肪氧合酶途径的替代分支的代谢通量的调节。
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.