Hu Yun, Zhong Ruiqin, Morrison W Herbert, Ye Zheng-Hua
Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
Planta. 2003 Oct;217(6):912-21. doi: 10.1007/s00425-003-1067-7. Epub 2003 Jul 3.
The Arabidopsis thaliana (L.) Heynh. ROOT HAIR DEFECTIVE3 (RHD3) gene has previously been shown to be essential for normal cell expansion [H. Wang et al. (1997) Genes Dev 11:799-811]. In this report, we demonstrated that mutation of the RHD3 gene in the Arabidopsis fragile fiber 4 (fra4) mutant caused a dramatic reduction in the wall thickness of fibers, vessels, and pith cells in the inflorescence stems and, concomitantly, a decrease in the mechanical strength of stems. The reduced wall thickness in the fra4 mutant was accompanied by an alteration in cell wall composition. Consistent with the defective fiber and vessel wall phenotypes, the RHD3 gene exhibited a strong expression in developing fiber and xylem cells. We showed that the Arabidopsis genome contains two additional RHD3-like genes, one of which was expressed specifically in flowers. In addition, we found that mutation of the RHD3 gene caused an alteration in the organization of the actin cytoskeleton but no effects on cortical microtubules. Our findings suggest an essential role of RHD3 in cell wall biosynthesis and actin organization, both of which are known to be important for cell expansion.
拟南芥（Arabidopsis thaliana (L.) Heynh.）的根毛缺陷3（ROOT HAIR DEFECTIVE3，RHD3）基因先前已被证明对正常细胞扩张至关重要[H. Wang等人（1997年），《基因与发育》11:799 - 811]。在本报告中，我们证明了拟南芥脆纤维4（fra4）突变体中RHD3基因的突变导致花序茎中纤维、导管和髓细胞的细胞壁厚度显著降低，同时茎的机械强度也降低。fra4突变体中细胞壁厚度的降低伴随着细胞壁成分的改变。与有缺陷的纤维和导管壁表型一致，RHD3基因在发育中的纤维和木质部细胞中强烈表达。我们表明拟南芥基因组还包含另外两个类RHD3基因，其中一个在花中特异性表达。此外，我们发现RHD3基因的突变导致肌动蛋白细胞骨架组织的改变，但对皮层微管没有影响。我们的研究结果表明RHD3在细胞壁生物合成和肌动蛋白组织中起着至关重要的作用，而这两者都已知对细胞扩张很重要。
