Abstract:

A full-length cDNA for lycopene β-cyclase (LYC-b) was isolated from carrot ( Daucus carota L.) roots by 5′ and 3′ RACE. The cDNA is 2 089 bp long with an open reading frame of 1 515 bp, which encodes a polypeptide of 505 amino acids. The deduced amino acid sequence of the cDNA is significantly conserved as compared with those of LYC-b from tomato ( Lycopersicum esculentum Mill.), tobacco ( Nicotiana rustica L.) and pepper (Capsicum frutescens L.), but with difference from those of the bacteria such as Agrobacterium aurantiacum Conn and Erwinia uredovora (Pon et al .) Mergaert et al . In contrast to orange roots of the variety CA201 which contains rich α- and β-carotene, and shows rather high level of the level of LYC-b mRNA, expression of the LYC-b is suppressed severely in purple roots of the variety “Qitouhong" containing high level of lycopene and low level of α- and β-carotene, leading apparent accumulation of the lycopene in “Qitouhong" roots due to low transcriptional activity of the LYC-b gene.

胡萝卜茄红素B-环化酶cDNA的分离及其在肉质根中的差异表达
陈大明*  薛颖 刘敬梅 王永健 陈杭
（北京市农林科学院蔬菜研究中心，北京100089）

摘要：利用 5′和 3′RACE技术从胡萝卜 (DaucuscarotaL .)肉质根中分离了茄红素 β_环化酶基因的全长cDNA。该cDNA长 2 0 89bp ,包含一个 15 15bp的开放阅读框架 ,所编码的肽链长 5 0 5个氨基酸 ,其一级结构与番茄 (Lycoper sicumesculentum Mill.)、烟草 (Nicotianarustica L .)和辣椒 (Capsicumfrutescens L .)等植物的茄红素 β-环化酶高度同源。茄红素 β-环化酶在胡萝卜肉质根中的表达受品种特异性的调控 ,在CA2 0 1胡萝卜肉质根中表达十分活跃 ,而在“齐头红”胡萝卜肉质根中该基因的表达受到了强烈的抑制 ,导致茄红素在细胞中大量积累

关键词： 胡萝卜；茄红素β-环化酶；类胡萝卜素生物合成；基因表达

Key words: carrot, lycopene β-cyclase, carotenogenesis, gene expression