豌豆卷须肌动蛋白Ⅱ类异型体cDNA克隆的序列分析

Sequence Analysis of Pea Tendril Actin Isoform Ⅱ cDNA Clones

分析１５个豌豆卷须肌动蛋白ｃＤＮＡ 克隆的限制性内切酶图谱，发现在豌豆卷须中至少存在三类肌动蛋白异型体，分别命名为Ⅰ类（ＰＥＡｃ Ⅰ）、Ⅱ类（ＰＥＡｃ Ⅱ）和Ⅲ类（ＰＥＡｃ Ⅲ）异型体．三类异型体的克隆数目分别为１０、４和１个，表明三类异型体在豌豆卷须中的表达是不同的，很可能具有组织或发育阶段的特异性．对Ⅱ类异型体的三个ｃＤＮＡ 克隆ＰＥＡｃ３、ＰＥＡｃ９和ＰＥＡｃ１１进行了全序列测定，所测定的序列已被ＧｅｎＢａｎｋ 数据库所接受．测序结果表明，ＰＥＡｃ３、ＰＥＡｃ９和ＰＥＡｃ１１的序列长度分别为１５５０、１６８０和１０９１个核苷酸，其中编码区长１１３４个核苷酸，编码的氨基酸长度为３７７（ＰＥＡｃ１１缺少编码氨基端前９６个氨基酸的核苷酸序列）．三个克隆的核苷酸序列完全相同，差别仅在于３′非翻译区的长度不同，即ｐｏｌｙ（Ａ）的加入位点不同．这说明它们可能是由同一基因转录而来，但转录后的加工过程不同．豌豆卷须中肌动蛋白基因ｐｏｌｙ（Ａ）加入位点的使用，可能与组织或发育的特异性表达有关．此外，豌豆卷须肌动蛋白三类异型体之间的核苷酸序列同源性为８０％ ，氨基酸序列同源性为９４％ ．

The restriction map of 15 pea tendril actin cDNA clones shows that there are at least three actin isoforms PEAc Ⅰ,PEAc Ⅱ and PEAc Ⅲ expressed in pea tendril.The numbers of the three isoforms are 10,4,and 1,respectively.This ratio implies that the expressions of the three isoforms in pea tendril are different and the actin gene expression may have tissue/development specificity.Sequence analysis of the three actin isoform Ⅱ cDNA clones,PEAc3,PEAc9 and PEAc11 revealed that they was 1 550 bp,1 680 bp and 1 091 bp in length,respectively.The nucleotide acid sequences of the three clones were identical,except the length of the 3′untranslated region.The coding region was 1 134 bp and coded for a 377 amino acid polypeptide.It means that they probably transcribed from the same gene,but the splicing mechanism was different.The result implies that the tissue/development specific expression of actin genes in the pea tendril might be mediated by the use of different polyadenylation signals.The nucleotide and deduced amino acid sequence homology of the three pea tendril actin isoforms are 80% and 94%.