Stumpe Michael, Bode Julia, Göbel Cornelia, Wichard Thomas, Schaaf Andreas, Frank Wolfgang, Frank Markus, Reski Ralf, Pohnert Georg, Feussner Ivo
Georg-August-University Göttingen, Albrecht-von-Haller-Institute for Plant Sciences, Department of Plant Biochemistry, Justus-von-Liebig-Weg 11, D-37077 Göttingen, Germany.
Biochim Biophys Acta. 2006 Mar;1761(3):301-12. doi: 10.1016/j.bbalip.2006.03.008. Epub 2006 Apr 4.
After wounding, the moss Physcomitrella patens emits fatty acid derived volatiles like octenal, octenols and (2E)-nonenal. Flowering plants produce nonenal from C18-fatty acids via lipoxygenase and hydroperoxide lyase reactions, but the moss exploits the C20 precursor arachidonic acid for the formation of these oxylipins. We describe the isolation of the first cDNA (PpHPL) encoding a hydroperoxide lyase from a lower eukaryotic organism. The physiological pathway allocation and characterization of a downstream enal-isomerase gives a new picture for the formation of fatty acid derived volatiles from lower plants. Expression of a fusion protein with a yellow fluorescent protein in moss protoplasts showed that PpHPL was found in clusters in membranes of plastids. PpHPL can be classified as an unspecific hydroperoxide lyase having a substrate preference for 9-hydroperoxides of C18-fatty acids but also the predominant substrate 12-hydroperoxy arachidonic acid is accepted. Feeding experiments using arachidonic acid show an increase in the 12-hydroperoxide being metabolized to C8-aldehydes/alcohols and (3Z)-nonenal, which is rapidly isomerized to (2E)-nonenal. PpHPL knock out lines failed to emit (2E)-nonenal while formation of C8-volatiles was not affected indicating that in contrast to flowering plants, PpHPL is only involved in formation of a specific subset of volatiles.
受伤后，小立碗藓会释放出脂肪酸衍生的挥发性物质，如辛烯醛、辛烯醇和（2E）-壬烯醛。开花植物通过脂氧合酶和氢过氧化物裂解酶反应从C18脂肪酸生成壬烯醛，但小立碗藓利用C20前体花生四烯酸来形成这些氧化脂质。我们描述了从一种低等真核生物中分离出的第一个编码氢过氧化物裂解酶的cDNA（PpHPL）。下游烯醛异构酶的生理途径分配和表征为低等植物脂肪酸衍生挥发性物质的形成提供了新的图景。在小立碗藓原生质体中表达与黄色荧光蛋白融合的蛋白表明，PpHPL存在于质体膜的簇中。PpHPL可归类为一种非特异性氢过氧化物裂解酶，对C18脂肪酸的9-氢过氧化物具有底物偏好，但也能接受主要底物12-氢过氧化花生四烯酸。使用花生四烯酸的饲喂实验表明，12-氢过氧化物代谢为C8醛/醇和（3Z）-壬烯醛的量增加，（3Z）-壬烯醛会迅速异构化为（2E）-壬烯醛。PpHPL基因敲除株系无法释放（2E）-壬烯醛，而C8挥发性物质的形成不受影响，这表明与开花植物不同，PpHPL仅参与特定子集挥发性物质的形成。
