条斑紫菜核糖体基因簇的研究

Porphyra yezoensis Ueda was chosen as a model organism of seaweed, is one of the most important species in science and in economy. The nori industry brings more than 2 billion US dollars annually in the world along these years. The whole industrial chain has been built in Jiangsu Province firstly in nori farm industry of China, or in the world. A dramatic change has taking place recently in the taxonomy of Porphyra sensu lata, the genus of Porphyra will be divided into 15 new genera, and the Porphyra yezoensis may be called Pyropia yezoensis. A lot of new species and new genera will be named according to the bases sequences of rbcL gene and 18S rDNA, the two house-keeping genes. These two gene sequenses applied by international seweed taxonomy researchers are too conserved to supply more useful information. In this study, the full-length ribosomal gene cluster of Porphyra yezoensis will be sequenced, the characters of bases conponents, variety scales and functions of individual part in 18S-ITS1-5.8S-ITS2-28S-IGS will be classified. The huge variety parts, such as ITS and IGS will supply more information in the species. The brand-new criterion will be brought out in taxonomy of Porphyra genus or seaweed.It will also be applied in the nori industry by attaching IGS molecular tags for every varieties.

条斑紫菜Porphyra yezoensis Ueda被认为是模式生物的候选海藻物种；还是最具经济价值的栽培海藻，其初级产品的年产值超过20亿美元。江苏省是我国主要栽培条斑紫菜的地区，形成了目前的全产业链经营模式。但是目前紫菜的分类在国际上正在经历巨大的变革，可能作为属的分类阶元都不复存在，而依据就是rbcL和18S rDNA的基因序列。以上2个基因都属于管家基因，其序列过于保守，提供的分子信息不多，本研究拟克隆条斑紫菜核糖体全长基因簇；分析18S-ITS1-5.8S-ITS2-28S-IGS各部分的碱基结构特点，变异程度；尤其是对变异较大的ITS和IGS的序列在该物种内部的变化情况做出解释说明，为该物种的分类地位确定提供参考，同时该研究提供的方法可以为该属或者更高的分类阶元的分子分类学提供依据。在生产实践上可以为紫菜良种提供IGS分子标签。

本研究首次克隆出条斑紫菜（Pyropia yezoensis）核糖体基因簇的全长序列，经分析发现该基因簇全长长度为13654bp——15130bp，序列包括几个部分：18S rDNA有0-2个内含子但外显子的序列几乎相同，且长度都为1834bp; 28S rDNA长度为4770bp，且不含内含子; ITS序列长度为1066bp以及IGS序列长度为5984bp。选取IGS序列的高度可变区，对我国主要的九个栽培品种的条斑紫菜进行了有效区分，得到序列长度在3628bp-3776bp之间，序列共有278个变异位点，约占总序列的7.5%。同时运用IGS区部分序列作为分子标签，对条斑紫菜减数分裂的问题进行了研究，证明了条斑紫菜叶状体是一个由不同遗传背景细胞构成的嵌合体，证实了紫菜减数分裂发生在壳孢子萌发时期。运用本项目获得的核糖体基因簇分子标记结果，分别对福建坛紫菜、福建海水红毛菜以及江苏浒苔进行了全长序列的测定，分别得到了全长15528bp的坛紫菜全序列，全长为12530bp的红毛菜全序列，全长为8948bp的浒苔全序列，并利用该结果分别进行了分子系统学研究，证明ITS是海藻种间分子分类的有效标记，IGS序列是种下鉴定的有效标记。