A role for β-sitosterol to stigmasterol conversion in plant-pathogen interactions
A role for β-sitosterol to stigmasterol conversion in plant-pathogen interactions
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DOI：
10.1111/j.1365-313x.2010.04235.x
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发表时间：
2010-07-01
期刊：
影响因子：
7.2
通讯作者：
Zeier, Juergen
中科院分区：
文献类型：
--
作者：
Griebel, Thomas;Zeier, Juergen
P>接种病原微生物后，植物会引起一系列代谢变化，这些变化可能有助于诱导抗性，甚至增强易感性。在分析拟南芥-丁香假单胞菌相互作用期间的叶脂组成时，我们发现植物甾醇豆甾醇的积累是细菌叶子感染时发生的重要植物代谢过程。豆甾醇是由细胞色素 P450 CYP710A1 通过 C22 去饱和从 β-谷甾醇合成的。与野生型植物相比，病原体诱导的 C22 去饱和酶表达和伴随的豆甾醇积累受损的拟南芥 cyp710A1 突变株系对无毒和强毒丁香假单胞菌菌株的抗性更强，并且外源应用豆甾醇减弱了这种抗性表型。这些数据表明，野生型植物中诱导的甾醇去饱和有利于病原体繁殖和植物易感性。豆甾醇的形成是通过感知病原体相关的分子模式（例如鞭毛蛋白和脂多糖）以及通过活性氧的产生而触发的，但不依赖于水杨酸、茉莉酸或乙烯防御途径。在叶子接种丁香假单胞菌后，分离的微粒体和质膜制剂表现出与全叶提取物类似的豆甾醇/β-谷甾醇比率的增加，表明产生的豆甾醇并入植物膜中。病原体攻击后叶片中豆甾醇含量的增加不会影响水杨酸介导的防御信号，但会减弱病原体诱导的防御调节剂黄素依赖性单加氧酶 1 的表达。因此，丁香假单胞菌通过刺激叶片中甾醇 C22 去饱和，从而增加植物膜中豆甾醇与 β-谷甾醇的比例，从而促进植物对疾病的易感性。
P>Upon inoculation with pathogenic microbes, plants induce an array of metabolic changes that potentially contribute to induced resistance or even enhance susceptibility. When analysing leaf lipid composition during the Arabidopsis thaliana-Pseudomonas syringae interaction, we found that accumulation of the phytosterol stigmasterol is a significant plant metabolic process that occurs upon bacterial leaf infection. Stigmasterol is synthesized from beta-sitosterol by the cytochrome P450 CYP710A1 via C22 desaturation. Arabidopsis cyp710A1 mutant lines impaired in pathogen-inducible expression of the C22 desaturase and concomitant stigmasterol accumulation are more resistant to both avirulent and virulent P. syringae strains than wild-type plants, and exogenous application of stigmasterol attenuates this resistance phenotype. These data indicate that induced sterol desaturation in wild-type plants favours pathogen multiplication and plant susceptibility. Stigmasterol formation is triggered through perception of pathogen-associated molecular patterns such as flagellin and lipopolysaccharides, and through production of reactive oxygen species, but does not depend on the salicylic acid, jasmonic acid or ethylene defence pathways. Isolated microsomal and plasma membrane preparations exhibited a similar increase in the stigmasterol/beta-sitosterol ratio as whole-leaf extracts after leaf inoculation with P. syringae, indicating that the stigmasterol produced is incorporated into plant membranes. The increased contents of stigmasterol in leaves after pathogen attack do not influence salicylic acid-mediated defence signalling but attenuate pathogen-induced expression of the defence regulator flavin-dependent monooxygenase 1. P. syringae thus promotes plant disease susceptibility through stimulation of sterol C22 desaturation in leaves, which increases the stigmasterol to beta-sitosterol ratio in plant membranes.