Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Centre, London, Ontario, Canada N5V 4T3.
Plant Physiol. 2012 Oct;160(2):917-28. doi: 10.1104/pp.112.202572. Epub 2012 Aug 3.
Remodeling of the plant cell cytoskeleton precedes symbiotic entry of nitrogen-fixing bacteria within the host plant roots. Here we identify a Lotus japonicus gene encoding a predicted ACTIN-RELATED PROTEIN COMPONENT1 (ARPC1) as essential for rhizobial infection but not for arbuscular mycorrhiza symbiosis. In other organisms ARPC1 constitutes a subunit of the ARP2/3 complex, the major nucleator of Y-branched actin filaments. The L. japonicus arpc1 mutant showed a distorted trichome phenotype and was defective in epidermal infection thread formation, producing mostly empty nodules. A few partially colonized nodules that did form in arpc1 contained abnormal infections. Together with previously described L. japonicus Nck-associated protein1 and 121F-specific p53 inducible RNA mutants, which are also impaired in the accommodation of rhizobia, our data indicate that ARPC1 and, by inference a suppressor of cAMP receptor/WASP-family verpolin homologous protein-ARP2/3 pathway, must have been coopted during evolution of nitrogen-fixing symbiosis to specifically mediate bacterial entry.
植物细胞细胞骨架的重塑先于固氮细菌在宿主植物根部的共生进入。在这里，我们鉴定出一个编码拟南芥肌动蛋白相关蛋白 1（ARPC1）的基因，该基因对根瘤菌的感染是必需的，但对丛枝菌根共生是不必要的。在其他生物中，ARPC1 构成 ARP2/3 复合物的一个亚基，该复合物是 Y 形分支肌动蛋白丝的主要成核因子。L. japonicus arpc1 突变体表现出扭曲的毛状体表型，表皮侵染线形成缺陷，产生大多数空根瘤。在 arpc1 中形成的少数部分定殖的根瘤含有异常侵染。与之前描述的 L. japonicus Nck 相关蛋白 1 和 121F 特异性 p53 诱导 RNA 突变体一起，它们也在根瘤菌的容纳方面受损，我们的数据表明，ARPC1 以及，推断为 cAMP 受体/WASP 家族 verpolin 同源蛋白-ARP2/3 途径的抑制剂，在固氮共生的进化过程中必须被共同选择，以专门介导细菌进入。
