该研究以铁观音茶树品种叶片为材料,通过RT-PCR技术,克隆了茶树脱落酸(ABA )合成途径关键限速酶——9-顺式环氧类胡萝卜素裂解双加氧酶(9-cis-epoxycarotenoid dioxygenase ,NCED )基因的全长cDNA序列.该基因cDNA全长1 931 bp ,包含1 821 bp完整开放阅读框,共编码606个氨基酸残基. NCBI同源分析结果表明,与葡萄VvNCED2相似性最高(78%) ,命名为CsNCED2(NCBI登录号:MF765770).氨基酸序列分析显示,其具有NCED家族的FLNO2258保守结构域,以及MIAHPKxDP和HDFAITE保守结构域序列;在保守区存在4个Fe2+活性组氨酸结合位点,N-端含有叶绿体转运肽.实时荧光定量PCR分析表明,CsNCED2基因在铁观音叶、茎和花中表达量较高;白茶萎凋和乌龙茶做青均可以诱导 CsNCED2基因显著上调表达;除干旱胁迫抑制 CsNCED2表达外,ABA和低温胁迫均能够诱导 CsNCED2基因显著上调表达.表明 CsNCED2基因在茶树ABA合成代谢以及胁迫响应中发挥重要作用.%The full length cDNA of the key rate-limiting enzyme gene CsNCED2 (9-cis-epoxycarotenoid dioxygenase ,NCED) in the ABA synthesis pathway was cloned by RT-PCR from the leaves of tea cultivar'Tieguanyin'in this study.The full length cDNA was 1 931 bp with an ORF of 1 821 bp ,encoding 606 a-mino acids with 78% homologous of the NCED2 from Vitis vinifera ,named as CsNCED2.Amino acid se-quence analysis showed that CsNCED2 contains three conserved domain FLNO2258 ,MIAHPKxDP and HDFAIT E ,being the characteristic feature of NCED gene families.It possessed four conserved histidine residues requiring Fe2+binding site and N-terminal chloroplast targeting transit peptides.Quantitative PCR analysis showed that the expression of CsNCED2 was highly in leaf ,stem and flower.White and Oo-long tea processing procedure could significantly up-regulate the expression of CsNCED2.The expression of CsNCED2 was significant up-regulate under the treatment of ABA and cold ,but repressed by drought. In conclusion ,CsNCED2 might play an important role in the ABA synthesis metabolism and the responses to different stress in tea plant.
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