Díaz-Camino Claudia, Conde Renaud, Ovsenek Nick, Villanueva Marco A
Departamento de Biología Molecular de Plantas, Instituto de Biotecnología, UNAM, Apartado Postal 510-3, Cuernavaca, Morelos 62250, México.
J Exp Bot. 2005 Feb;56(412):557-65. doi: 10.1093/jxb/eri034. Epub 2004 Nov 29.
Previous analysis of actin in a dicotyledonous plant, Phaseolus vulgaris (or common bean), showed very low actin levels in cotyledons but they were concentrated in the embryo axis. Upon imbibition, actin expression increased 5-fold and a maximum of four actin isoforms were observed, two of them transient and two major ones were steadily expressed. In this work, analysis of the actin expression in a monocotyledonous plant, Zea mays (or maize), and over a longer period of germination/growth, showed that striking similarities exist. Actin is present in all the seed components, but it is mainly concentrated in the embryo axis. The expression of maize actin was induced during post-imbibition at both the protein and mRNA levels. Sharp increases in actin appeared from 24-48 h and again from 72-96 h. A more modest and steady actin mRNA increase in expression was observed; however, it did not appear as dramatic as in the case of common bean due to the presence of readily detectable amounts of message in the dry maize seed. The isoform distribution in the dry seed showed a pattern of at least three isovariants of pIs approximately 5.0, 5.1, and 5.2, which were differentially expressed at the various post-imbibition times analysed. Two of the actin isoforms at 48 h post-imbibition cross-reacted with a phosphotyrosine-specific antibody and they are the product of three expressed genes as shown by in vitro translation assays. These data indicate that maize actin protein and mRNA expression is induced upon the trigger of germination, and the isoform expression kinetics and patterns resemble those from bean, suggesting that, in both species, actin expression at these early germination/growth stages is a highly regulated event.
先前对双子叶植物菜豆（Phaseolus vulgaris）肌动蛋白的分析表明，子叶中的肌动蛋白水平非常低，但它们集中在胚轴中。吸胀后，肌动蛋白表达增加了5倍，最多观察到四种肌动蛋白同工型，其中两种是瞬时的，两种主要的同工型稳定表达。在这项研究中，对单子叶植物玉米（Zea mays）在更长的萌发/生长周期内的肌动蛋白表达进行分析，结果显示存在显著的相似性。肌动蛋白存在于所有种子成分中，但主要集中在胚轴中。玉米肌动蛋白的表达在吸胀后在蛋白质和mRNA水平上均被诱导。肌动蛋白在24 - 48小时以及72 - 96小时出现急剧增加。观察到肌动蛋白mRNA表达有较为适度且稳定的增加；然而，由于干玉米种子中存在易于检测到的mRNA量，其增加不如菜豆那样显著。干种子中的同工型分布显示出至少三种等变体的模式，其等电点约为5.0、5.1和5.2，在分析的不同吸胀后时间差异表达。吸胀后48小时的两种肌动蛋白同工型与磷酸酪氨酸特异性抗体发生交叉反应，体外翻译分析表明它们是三个表达基因的产物。这些数据表明，玉米肌动蛋白的蛋白质和mRNA表达在萌发触发时被诱导，同工型表达动力学和模式与菜豆相似，这表明在这两个物种中，这些早期萌发/生长阶段肌动蛋白的表达是一个高度受调控的事件。
