Diet Anouck, Link Bruce, Seifert Georg J, Schellenberg Barbara, Wagner Ulrich, Pauly Markus, Reiter Wolf-Dieter, Ringli Christoph
Institute of Plant Biology, University of Zürich, 8008 Zürich, Switzerland.
Plant Cell. 2006 Jul;18(7):1630-41. doi: 10.1105/tpc.105.038653. Epub 2006 Jun 9.
Cell and cell wall growth are mutually dependent processes that must be tightly coordinated and controlled. LRR-extensin1 (LRX1) of Arabidopsis thaliana is a potential regulator of cell wall development, consisting of an N-terminal leucine-rich repeat domain and a C-terminal extensin-like domain typical for structural cell wall proteins. LRX1 is expressed in root hairs, and lrx1 mutant plants develop distorted root hairs that often swell, branch, or collapse. The aberrant cell wall structures found in lrx1 mutants point toward a function of LRX1 during the establishment of the extracellular matrix. To identify genes that are involved in an LRX1-dependent developmental pathway, a suppressor screen was performed on the lrx1 mutant, and two independent rol1 (for repressor of lrx1) alleles were isolated. ROL1 is allelic to Rhamnose Biosynthesis1, which codes for a protein involved in the biosynthesis of rhamnose, a major monosaccharide component of pectin. The rol1 mutations modify the pectic polysaccharide rhamnogalacturonan I and, for one allele, rhamnogalacturonan II. Furthermore, the rol1 mutations cause a change in the expression of a number of cell wall-related genes. Thus, the lrx1 mutant phenotype is likely to be suppressed by changes in pectic polysaccharides or other cell wall components.
细胞和细胞壁生长是相互依赖的过程，必须紧密协调和控制。拟南芥的富含亮氨酸重复序列伸展蛋白1（LRX1）是细胞壁发育的潜在调节因子，由一个N端富含亮氨酸重复序列结构域和一个C端类似伸展蛋白结构域组成，这是结构细胞壁蛋白的典型结构。LRX1在根毛中表达，lrx1突变体植株发育出扭曲的根毛，这些根毛经常肿胀、分支或塌陷。在lrx1突变体中发现的异常细胞壁结构表明LRX1在细胞外基质形成过程中发挥作用。为了鉴定参与LRX1依赖性发育途径的基因，对lrx1突变体进行了抑制子筛选，并分离出两个独立的rol1（lrx1的抑制子）等位基因。ROL1与鼠李糖生物合成1基因等位，该基因编码一种参与鼠李糖生物合成的蛋白质，鼠李糖是果胶的主要单糖成分。rol1突变改变了果胶多糖鼠李半乳糖醛酸聚糖I，对于一个等位基因，还改变了鼠李半乳糖醛酸聚糖II。此外，rol1突变导致许多细胞壁相关基因的表达发生变化。因此，lrx1突变体表型可能被果胶多糖或其他细胞壁成分的变化所抑制。
