An Arabidopsis ACT2 dominant-negative mutation, which disturbs F-actin polymerization, reveals its distinctive function in root development
An Arabidopsis ACT2 dominant-negative mutation, which disturbs F-actin polymerization, reveals its distinctive function in root development
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DOI：
10.1093/pcp/pcg158
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发表时间：
2003-11-01
影响因子：
4.9
通讯作者：
Okada, K
中科院分区：
文献类型：
--
作者：
Nishimura, T;Yokota, E;Okada, K
拟南芥中存在8个肌动蛋白功能基因。这些基因在功能丧失突变体中的功能表征是困难的，因为高度保守的同种异体通常在相同的组织中表达。我们分离到了肌动蛋白基因ACT2的一个新的半显性突变等位基因(ACT2-2D)，它的错义突变导致了ACT2蛋白表面的氨基酸替换。ACT2启动子：：ACT2-2D转基因植株表现出与ACT2-2D相同的表型，表明ACT2-2D是一个显性-负性突变体。ACT2-2D在根毛的起始和伸长、根表皮细胞的伸长和地上部分的生长方面存在缺陷。具体地说，根表皮的成毛细胞减少了径向细胞的扩张，偶尔会发生细胞死亡，而根表皮的成毛细胞则没有。相反，根分生组织中的细胞分裂模式没有受到影响。ACT2-3是一个功能缺失的ACT2突变体，并没有发生这些形态异常中的大部分。ACT2-2D根表皮细胞中的肌动蛋白细丝(F-肌动蛋白)束短于野生型和功能丧失突变体。我们的结论是，F-肌动蛋白聚合缺陷以显性-负性方式导致细胞形态异常，ACT2在细胞伸长和根毛形成中发挥作用。
Eight functional actin genes are present in Arabidopsis. The functional characterization of these genes in loss-of-function mutants is difficult, because highly conserved isovariants are generally expressed in the same tissue. We isolated a novel semi-dominant mutant allele (act2-2D) of an actin gene, ACT2, with a missense mutation which causes an amino acid substitution at the surface of the ACT2 protein. ACT2 promoter::ACT2-2D transgenic plants showed the same phenotype as act2-2D, indicating that act2-2D is a dominant-negative mutant. act2-2D exhibited defects in the initiation and elongation of root hairs, the elongation of root epidermal cells, and growth in aerial portions. Specifically, radial cell expansion was reduced and occasional cell death occurred in trichoblasts but not in atrichoblasts of the root epidermis. In contrast, cell division patterns in the root meristem were not affected. act2-3, a loss-of-function ACT2 mutant, did not develop most of these morphological abnormalities. Actin filament (F-actin) bundles in root epidermal cells of act2-2D were shorter than in the wild type and in the loss-of-function mutant. We conclude that defective F-actin polymerization caused the aberrant cell morphology in a dominant-negative manner, and that ACT2 functions in cell elongation and root hair formation.