Homogalacturonan synthesis in Arabidopsis thaliana requires a Golgi-localized protein with a putative methyltransferase domain
Homogalacturonan synthesis in Arabidopsis thaliana requires a Golgi-localized protein with a putative methyltransferase domain
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DOI：
10.1111/j.1365-313x.2007.03086.x
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发表时间：
2007-05-01
期刊：
影响因子：
7.2
通讯作者：
Hofte, Herman
中科院分区：
文献类型：
--
作者：
Mouille, Gregory;Ralet, Marie-Christine;Hofte, Herman
果胶是一种复杂的细胞壁多糖，其生物合成仍然知之甚少。我们确定了一个新的基因座，QUASIMODO 2（QUA 2）的细胞粘附减少的侏儒突变体。与野生型相比，qua 2 -1的同型半乳糖醛酸（HG）含量降低了50%，而不影响其他细胞壁多糖。qua 2 -1中剩余的HG显示出未改变的甲酯化度。定位克隆和GFP融合表明，QUA 2，在HG合成中的作用一致，编码高尔基体定位的蛋白质。与另一种高尔基体定位的HG合成所需的蛋白质QUA 1相反，QUA 2不显示与糖基转移酶的序列相似性，而是含有推定的甲基转移酶（MT）结构域。拟南芥基因组编码29个QUA 2相关蛋白。有趣的是，QUA 1和QUA 2的转录谱是相关的，并且可以鉴定具有相关转录谱的其他QUA 1和QUA 2同源物对。总之，这些结果导致了QUA 2是果胶MT的假设，并且高半乳糖醛酸聚糖的聚合和甲基化是相互依赖的反应。
Pectins are a family of complex cell-wall polysaccharides, the biosynthesis of which remains poorly understood. We identified dwarf mutants with reduced cell adhesion at a novel locus, QUASIMODO2 (QUA2). qua2-1 showed a 50% reduction in homogalacturonan (HG) content compared with the wild type, without affecting other cell-wall polysaccharides. The remaining HG in qua2-1 showed an unaltered degree of methylesterification. Positional cloning and GFP fusions showed that QUA2, consistent with a role in HG synthesis, encodes a Golgi-localized protein. In contrast to QUA1, another Golgi-localized protein required for HG-synthesis, QUA2 does not show sequence similarity to glycosyltransferases, but instead contains a putative methyltransferase (MT) domain. The Arabidopsis genome encodes 29 QUA2-related proteins. Interestingly, the transcript profiles of QUA1 and QUA2 are correlated and other pairs of QUA1 and QUA2 homologues with correlated transcript profiles can be identified. Together, the results lead to the hypothesis that QUA2 is a pectin MT, and that polymerization and methylation of homogalacturonan are interdependent reactions.