Kandasamy Muthugapatti K, McKinney Elizabeth C, Meagher Richard B
Department of Genetics, University of Georgia, Athens, Georgia 30602, USA.
Cell Motil Cytoskeleton. 2002 May;52(1):22-32. doi: 10.1002/cm.10029.
Profilin is a low-molecular weight, actin monomer-binding protein that regulates the organization of actin cytoskeleton in eukaryotes, including higher plants. Unlike the simple human or yeast systems, the model plant Arabidopsis has an ancient and highly divergent multi-gene family encoding five distinct profilin isovariants. Here we compare and characterize the regulation of these profilins in different organs and during microspore development using isovariant-specific monoclonal antibodies. We show that PRF1, PRF2, and PRF3 are constitutive, being strongly expressed in all vegetative tissues at various stages of development. These profilin isovariants are also predominant in ovules and microspores at the early stages of microsporogenesis. In contrast, PRF4 and PRF5 are late pollen-specific and are not detectable in other cell types of the plant body including microspores and root hairs. Immunocytochemical studies at the subcellular level reveal that both the constitutive and pollen-specific profilins are abundant in the cytoplasm. In vegetative cell types, such as root apical cells, profilins showed localization to nuclei in addition to the cytoplasmic staining. The functional diversity of profilin isovariants is discussed in light of their spatio-temporal regulation during vegetative development, pollen maturation, and pollen tube growth.
肌动蛋白结合蛋白是一种低分子量的肌动蛋白单体结合蛋白，可调节真核生物（包括高等植物）中肌动蛋白细胞骨架的组织。与简单的人类或酵母系统不同，模式植物拟南芥有一个古老且高度分化的多基因家族，编码五种不同的肌动蛋白结合蛋白同工型。在这里，我们使用同工型特异性单克隆抗体比较并表征了这些肌动蛋白结合蛋白在不同器官和小孢子发育过程中的调控。我们发现PRF1、PRF2和PRF3是组成型的，在发育的各个阶段在所有营养组织中都强烈表达。这些肌动蛋白结合蛋白同工型在小孢子发生早期的胚珠和小孢子中也占主导地位。相比之下，PRF4和PRF5是晚期花粉特异性的，在植物体内的其他细胞类型（包括小孢子和根毛）中无法检测到。亚细胞水平的免疫细胞化学研究表明，组成型和花粉特异性肌动蛋白结合蛋白在细胞质中都很丰富。在营养细胞类型中，如根尖细胞，肌动蛋白结合蛋白除了细胞质染色外，还显示定位于细胞核。根据它们在营养发育、花粉成熟和花粉管生长过程中的时空调控，讨论了肌动蛋白结合蛋白同工型的功能多样性。
