Violaxanthin de-epoxidase (VDE) plays an important role in protecting the photosynthetic apparatus from photo-damage by dissipating excessively absorbed light energy as heat, via the conversion of violaxanthin (V) to intermediate product antheraxanthin (A) and final product zeaxanthin (Z) under high light stress. We have cloned a violaxanthin de-epoxidase gene (CsVDE) from cucumber. The amino acid sequence of CsVDE has high homology with VDEs in other plants. RT-PCR analysis and histochemical staining show that CsVDE is expressed in all green tissues in cucumber and Arabidopsis. Using GFP fusion protein and immunogold labeling methods, we show that CsVDE is mainly localized in chloroplasts in cucumber. Under high light stress, relative expression of CsVDE and the de-epoxidation ratio (A+Z)/(V+A+Z) is increased rapidly, and abundance of the gold particles was also increased. Furthermore, CsVDE is quickly induced by cold and drought stress, reaching maximum levels at the 2nd hour and the 9th day, respectively. The ratio of (A+Z)/(V+A+Z) and non-photochemical quenching (NPQ) is reduced in transgenic Arabidopsis down-regulated by the antisense fragment of CsVDE, compared to wild type (WT) Arabidopsis under high light stress. This indicates decreased functionality of the xanthophyll cycle and increased sensitivity to photoinhibition of photosystem II (PSII) in transgenic Arabidopsis under high light stress.
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机译:紫黄质脱环氧化酶(VDE)通过将紫黄质(V)转化为中间产物花药黄嘌呤(A)和最终产物玉米黄质(Z),将过量吸收的光能作为热量散发,从而在保护光合装置免受光损伤方面起着重要作用。 )在高光照下。我们已经从黄瓜中克隆了紫黄质脱环氧酶基因(CsVDE)。 CsVDE的氨基酸序列与其他植物中的VDE具有高度同源性。 RT-PCR分析和组织化学染色显示CsVDE在黄瓜和拟南芥的所有绿色组织中都有表达。使用GFP融合蛋白和免疫金标记方法,我们表明CsVDE主要位于黄瓜的叶绿体中。在高光胁迫下,CsVDE的相对表达和脱环氧化比(A + Z)/(V + A + Z)迅速增加,金颗粒的丰度也增加。此外,寒冷和干旱胁迫很快诱导了CsVDE,分别在第二天和第九天达到最高水平。与强光下的野生型拟南芥相比,CsVDE反义片段下调的转基因拟南芥中(A + Z)/(V + A + Z)与非光化学猝灭(NPQ)的比率降低强调。这表明在高光胁迫下,转基因拟南芥中叶黄素循环的功能降低,并且对光系统II(PSII)的光抑制敏感性增加。
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