The reb1-1 mutation of Arabidopsis.: Effect on the structure and localization of galactose-containing cell wall polysaccharides
The reb1-1 mutation of Arabidopsis.: Effect on the structure and localization of galactose-containing cell wall polysaccharides
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DOI：
10.1104/pp.105.074997
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发表时间：
2006-04-01
期刊：
影响因子：
7.4
通讯作者：
Driouich, A
中科院分区：
文献类型：
--
作者：
Nguema-Ona, E;Andème-Onzighi, C;Driouich, A
拟南芥（Arabidopsis thaliana）根表皮凸起1 - 1（reb1 - 1）突变体（与根毛缺陷1 [rhd 1]等位）的特征在于根伸长速率降低和毛细胞凸起。REB1/RHD1基因属于参与D-半乳糖（Gal）合成的UDP-D-葡萄糖4-差向异构酶家族。我们以前的研究表明，某些阿拉伯半乳聚糖蛋白表位在突变体的凸出毛母细胞中不表达。在这项研究中，使用显微镜和生物化学方法相结合，我们已经调查了发生和三个主要的含半乳糖的多糖，即木葡聚糖（XyG），鼠李糖半乳糖醛酸（RG）-I，和RG-II的突变体根细胞壁的结构。我们的免疫细胞化学数据显示，肿胀的毛细胞未被特异性针对XyG的α-L-Fucp-（1-> 2）-β-D-Galp侧链的单克隆抗体CCRC-M1染色，而它们被特异性针对XyG骨架的抗XyG抗体染色。此外，从根的半纤维素部分的分析表明，reb1 - 1中存在两个结构不同的XyGs。一种在结构上类似于野生型XyG，另一种缺乏岩藻半乳糖基化侧链并具有不溶性的特征。类似于抗XyG抗体，抗柴胡2IIC，特异性半乳糖基表位与果胶的多克隆抗体，染色的野生型和reb1 - 1的所有根表皮细胞。同样，抗RG-II抗体也对突变体中肿胀的毛细胞进行染色。此外，果胶聚合物的结构分析显示，RG-I和RG-II的半乳糖基化从reb1 - 1根细胞分离没有变化。这些发现表明reb1 - 1突变影响XyG结构，但不影响果胶多糖的结构，从而支持Gal的生物合成以及复杂多糖的半乳糖基化在聚合物水平上受到调节的假设。
The Arabidopsis ( Arabidopsis thaliana) root epidermal bulger1-1 (reb1-1) mutant ( allelic to root hair defective1 [rhd1]) is characterized by a reduced root elongation rate and by bulging of trichoblast cells. The REB1/RHD1 gene belongs to a family of UDP-D-Glucose 4-epimerases involved in the synthesis of D-Galactose ( Gal). Our previous study showed that certain arabinogalactan protein epitopes were not expressed in bulging trichoblasts of the mutant. In this study, using a combination of microscopical and biochemical methods, we have investigated the occurrence and the structure of three major Gal-containing polysaccharides, namely, xyloglucan (XyG), rhamnogalacturonan (RG)-I, and RG-II in the mutant root cell walls. Our immunocytochemical data show that swollen trichoblasts were not stained with the monoclonal antibody CCRC-M1 specific for alpha-L-Fucp-(1 -> 2)-beta-D-Galp side chains of XyG, whereas they were stained with anti-XyG antibodies specific for XyG backbone. In addition, analysis of a hemicellulosic fraction from roots demonstrates the presence of two structurally different XyGs in reb1-1. One is structurally similar to wild-type XyG and the other is devoid of fuco-galactosylated side chains and has the characteristic of being insoluble. Similar to anti-XyG antibodies, anti-bupleuran 2IIC, a polyclonal antibody specific for galactosyl epitopes associated with pectins, stained all root epidermal cells of both wild type and reb1-1. Similarly, anti-RG-II antibodies also stained swollen trichoblasts in the mutant. In addition, structural analysis of pectic polymers revealed no change in the galactosylation of RG-I and RG-II isolated from reb1-1 root cells. These findings demonstrate that the reb1-1 mutation affects XyG structure, but not that of pectic polysaccharides, thus lending support to the hypothesis that biosynthesis of Gal as well as galactosylation of complex polysaccharides is regulated at the polymer level.