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首页> 外文期刊>Journal of Experimental Botany >Cloning and characterization of two 9-cis-epoxycarotenoid dioxygenase genes, differentially regulated during fruit maturation and under stress conditions, from orange (Citrus sinensis L. Osbeck)
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Cloning and characterization of two 9-cis-epoxycarotenoid dioxygenase genes, differentially regulated during fruit maturation and under stress conditions, from orange (Citrus sinensis L. Osbeck)

机译：橙（Citrus sinensis L.Osbeck）的两个9-顺式-环氧类胡萝卜素双加氧酶基因的克隆和鉴定，在果实成熟过程中和在胁迫条件下受到不同的调控

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摘要

There is now biochemical and genetic evidence that oxidative cleavage of cis-epoxycarotenoids by 9-cis-epoxycarotenoid dioxygenase (NCED) is the critical step in the regulation of abscisic acid (ABA) synthesis in higher plants. The peel of Citrus fruit accumulates large amounts of ABA during maturation. To understand the regulation of ABA biosynthesis in Citrus, two full-length cDNAs (CsNCED1 and CsNCED2) encoding NCEDs were isolated and characterized from the epicarp of orange fruits (Citrus sinensis L. Osbeck). Expression of the CsNCED1 gene increased in the epicarp during natural and ethylene-induced fruit maturation, and in water-stressed leaves, in a pattern consistent with the accumulation of ABA. The second gene, CsNCED2, was not detected in dehydrated leaves and, in fruits, exhibited a differential expression to that of CsNCED1. Taken together, these results suggests that CsNCED1 is likely to play a primary role in the biosynthesis of ABA in both leaves and fruits, while CsNCED2 appears to play a subsidiary role restricted to chromoplast-containing tissue. Furthermore, analysis of 9-cis-violaxanthin and 9′-cis-neoxanthin, as the two possible substrates for NCEDs, revealed that the former was the main carotenoid in the outer coloured part of the fruit peel as the fruit ripened or after ethylene treatment, whereas 9′-cis-neoxanthin was not detected or was in trace amounts. By contrast, turgid and dehydrated leaves contained 9′-cis-neoxanthin but 9-cis-violaxanthin was absent. Based on these results, it is suggested that 9-cis-violaxanthin may be the predominant substrate for NCED in the peel of Citrus fruits, whereas 9′-cis-neoxanthin would be the precursor of ABA in photosynthetic tissues.
机译：现在有生化和遗传证据表明，9-顺式-环氧类胡萝卜素双加氧酶（NCED）氧化裂解顺式-环氧类胡萝卜素是调节高等植物中脱落酸（ABA）合成的关键步骤。柑橘类水果的果皮在成熟过程中会积累大量的ABA。为了了解柑橘中ABA生物合成的调控，从橙果（柑桔（Citrus sinensis L. Osbeck））的果皮中分离了两个编码NCED的全长cDNA（CsNCED1和CsNCED2）。在自然和乙烯诱导的果实成熟过程中，果皮中的CsNCED1基因的表达增加，而在水分胁迫的叶片中，CsNCED1基因的表达与ABA的积累一致。在脱水的叶子中未检测到第二个基因CsNCED2，并且在水果中显示出与CsNCED1的差异表达。综上所述，这些结果表明，CsNCED1可能在叶片和果实的ABA生物合成中起主要作用，而CsNCED2似乎起限于含色质体组织的辅助作用。此外，对9-顺式黄嘌呤和9'-顺式黄嘌呤作为NCEDs的两种可能底物的分析表明，前者是果实成熟或乙烯处理后果皮外部有色部分的主要类胡萝卜素。 ，而9'-顺式黄嘌呤未检出或为痕量。相比之下，参差不齐且脱水的叶子含有9'-顺式黄嘌呤，而9-顺式紫黄质则不存在。基于这些结果，表明9-顺式紫黄质可能是柑桔果皮中NCED的主要底物，而9'-顺式黄嘌呤可能是光合组织中ABA的前体。

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