An Y Q, McDowell J M, Huang S, McKinney E C, Chambliss S, Meagher R B
Department of Genetics, University of Georgia, Athens 30602, USA.
Plant J. 1996 Jul;10(1):107-21. doi: 10.1046/j.1365-313x.1996.10010107.x.
Arabidopsis has a complex and ancient actin gene family encoding six divergent subclasses of proteins. One subclass is represented by ACT2 and ACT8, which encode nearly identical proteins. These two genes differ significantly in flanking and intron sequences and in silent nucleotide positions within codons. Gene-specific RNA gel blot hybridization and reverse transcriptase-mediated polymerase chain reaction (RT-PCR) assays showed that ACT2 and/or ACT8mRNAs were coordinately and strongly expressed in leaves, roots, stems, flowers, pollen, and siliques. Together they account for greater than 80% of the actin mRNA in most Arabidopsis organs. The 5' flanking regions, including the promoter, the mRNA leader exon, an intron in the mRNA leader, and the first 19 codons, were coupled to a beta-glucuronidase (GUS) reporter gene and transformed into Arabidopsis. The ACT2/GUS construct was expressed strongly in nearly all the vegetative tissues in seedlings, juvenile plants, and mature plants. These activities persisted in older tissues. Little or no expression was observed in seed coats, hypocotyls, gynoecia, or pollen sacs. In contrast, the expression of the ACT8/GUS construct was weaker. It was observed only in a subset of the organs and tissues expressing ACT2/GUS and was not significantly expressed in the flower. ACT2, ACT8, and ACT8/GUS mRNAs were present at moderate to high levels in pollen, and yet neither ACT2/GUS nor ACT8/GUS enzyme expression could be detected in pollen. This suggested a mechanism of translational control affecting ACT2 and ACT8 expression in some tissues. The conservation of protein sequence and overlapping patterns of expression, in spite of significant DNA sequence divergence, suggests that the function and regulation of these two genes have been conserved during the evolution of the Brassicaceae.
拟南芥有一个复杂且古老的肌动蛋白基因家族，该家族编码六种不同亚类的蛋白质。其中一个亚类由ACT2和ACT8代表，它们编码几乎相同的蛋白质。这两个基因在侧翼和内含子序列以及密码子内的沉默核苷酸位置上有显著差异。基因特异性RNA凝胶印迹杂交和逆转录酶介导的聚合酶链反应（RT-PCR）分析表明，ACT2和/或ACT8 mRNA在叶、根、茎、花、花粉和角果中协同且强烈表达。在大多数拟南芥器官中，它们共同占肌动蛋白mRNA的80%以上。将包括启动子、mRNA前导外显子、mRNA前导中的一个内含子以及前19个密码子在内的5'侧翼区域与β-葡萄糖醛酸酶（GUS）报告基因连接，并转化到拟南芥中。ACT2/GUS构建体在幼苗、幼龄植物和成熟植物的几乎所有营养组织中都强烈表达。这些活性在较老的组织中持续存在。在种皮、下胚轴、雌蕊或花粉囊中几乎没有观察到表达。相比之下，ACT8/GUS构建体的表达较弱。仅在表达ACT2/GUS的器官和组织的一个子集中观察到它，并且在花中没有明显表达。ACT2、ACT8和ACT8/GUS mRNA在花粉中以中度至高水平存在，但在花粉中均未检测到ACT2/GUS和ACT8/GUS酶的表达。这表明在某些组织中存在影响ACT2和ACT8表达的翻译控制机制。尽管DNA序列存在显著差异，但蛋白质序列的保守性和重叠的表达模式表明，这两个基因的功能和调控在十字花科的进化过程中得以保留。
