Instituto Botánico, Departamento de Ciencia y Tecnología Agroforestal y Genética, Facultad de Farmacia, Universidad de Castilla-La Mancha, Campus Universitario s/n, 02071 Albacete, Spain.
J Exp Bot. 2012 Jan;63(2):681-94. doi: 10.1093/jxb/err293. Epub 2011 Nov 2.
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. ABA has been associated with dormancy and flower senescence, while also regulating plant adaptive responses to various environmental stresses. An NCED gene, CstNCED, was cloned from Crocus sativus stigmas. The deduced amino acid sequence of the CstNCED protein shared high identity with other monocot NCEDs, and was closely related to the liliopsida enzymes. At the N-terminus of CstNCED a chloroplast transit peptide sequence is located. However, its expression in chloroplast-free tissues suggested localization in other plastid types. The relationship between expression of CstNCED and the endogenous ABA level was investigated in the stigma and corms, where it was developmentally regulated. The senescence of the unpollinated stigma is preceded by an increase in ABA levels and CstNCED expression. In corms, a correlation was observed between CstNCED expression and dormancy. Furthermore, CstNCED expression was correlated with the presence of zeaxanthin in the dormant corms. When detached C. sativus leaves and stigmas were water and salt stressed, increases in CstNCED mRNA were observed. The results provided evidence of the involvement of CstNCED in the regulation of ABA-associated processes such as flower senescence and corm dormancy in monocotyledonous saffron.
顺式环氧类胡萝卜素在 9-顺式环氧类胡萝卜素双加氧酶（NCED）的作用下发生氧化裂解，这是高等植物中脱落酸（ABA）合成调控的关键步骤。ABA 与休眠和花衰老有关，同时也调节植物对各种环境胁迫的适应性反应。从番红花柱头中克隆出一个 NCED 基因 CstNCED。CstNCED 蛋白的推导氨基酸序列与其他单子叶植物 NCEDs 高度同源，与百合科的酶密切相关。CstNCED 在 N 端有一个质体转运肽序列。然而，其在无叶绿体组织中的表达表明其定位于其他类型的质体中。研究了 CstNCED 的表达与柱头和球茎中内源性 ABA 水平之间的关系，发现其在发育过程中受到调控。未授粉柱头的衰老先于 ABA 水平和 CstNCED 表达的增加。在球茎中，CstNCED 表达与休眠之间存在相关性。此外，CstNCED 表达与休眠球茎中玉米黄质的存在相关。当番红花离体叶片和柱头受到水分和盐分胁迫时，CstNCED mRNA 增加。结果提供了证据表明 CstNCED 参与了调控单叶类番红花中与 ABA 相关的过程，如花衰老和球茎休眠。
