Abstract:

Pea (Pisum sativum Linn.) actin gene family contains at least three isoforms(PEAcⅠ, PEAcⅡand PEAcⅢ), and the DNA sequence of these isoforms show high similarity in the coding regions and significant divergence in the untranslated regions. RT-PCR and Southern blotting using 3′-untranslated region (3′-UTR) as specific probe revealed that pea isoactin genes were expressed in roots, stems, leaves, tendrils, pollen and juvenile siliques, but displayed different patterns of transcript accumulation. Two fold serial dilution electrophoresis showed PEAcⅠ mRNA preferentially accumulated in rapidly developing tissues: it peaked in seven days' stem; remained at a rather high level in leaves within a month but decreased sign ificantly later; varied a little in tendrils and reached a median and a very low level respectively in juvenile siliques and in pollen. PEAcⅡ displayed somewhat similar expression pattern to PEAcⅠ. The observed differences in sequences and transcript accumulation patterns suggest that the individual pea actin genes may differ in their transcriptional regulation and cellular function. Phylogenetic tree of actins showed that pea actin isoforms are as diverged from each other as they are from other plant actins, and pea actins might have originated from a common ancestor before the divergence of the dicot and monocot plants.

豌豆肌动蛋白异型体的表达与系统发生分析
江元清 赵武玲*

（中国农业大学生物学院植物生理学与生物化学国家重点实验室，北京100094）

摘要： 豌豆 (Pisum sativum Linn .)肌动蛋白基因至少可以分为 3类异型体 :PEAcⅠ、PEAcⅡ和PEAcⅢ ,它们的编码区序列相似性很高 ,而非编码区序列存在显著的差异。RT_PCR和以 3′端非翻译区作探针的Southern杂交结果显示豌豆肌动蛋白异型体基因在根、茎、叶、卷须、花粉和幼嫩果实中均表达 ,但表达强度存在明显差异。利用连续稀释电泳对PEAcⅠ的转录本水平进行分析后发现它倾向于在幼嫩的器官中表达 ,且在 7d的茎中表达最强 ;在一个月内的叶片中表达也较强 ,此后明显下降 ;卷须中表达变化不显著 ,在花粉中表达很弱 ,在幼嫩荚果中的表达亦较多。PEAcⅡ表达特点与PEAcⅠ具有某些相似性。根据肌动蛋白序列重建的系统发生树表明豌豆肌动蛋白 3类异型体间的分歧明显 ,但起源于单、双子叶植物分化前的共同基因祖先。推测豌豆肌动蛋白异型体基因在转录调控和细胞功能上存在差异。

关键词： 肌动蛋白；)2端非翻译区；差异表达；分子进化；豌豆

通讯作者。Tel: + 86 (0) 10 62892672;Fax:+ 86 (0)10 62891332

Key words: actin, 3′-untranslated region (3′-UTR), differential expression, molecular evolution, pea (Pisum sativum)