The sulfate transporter SST1 is crucial for symbiotic nitrogen fixation in Lotus japonicus root nodules
The sulfate transporter SST1 is crucial for symbiotic nitrogen fixation in Lotus japonicus root nodules
复制标题
DOI：
10.1105/tpc.104.030106
复制
发表时间：
2005-05-01
期刊：
影响因子：
11.6
通讯作者：
Udvardi, MK
中科院分区：
文献类型：
--
作者：
Krusell, L;Krause, K;Udvardi, MK
豆科植物根瘤细胞内根瘤菌的共生固氮需要寄主细胞与寄主细菌之间的营养物质交换。在分子水平上对介导这种交换的植物转运蛋白知之甚少。几种模式豆科植物日本莲花的突变体在共生条件下发育出具有代谢缺陷的根瘤，不能有效地固定氮，并表现出生长迟缓。对两个这样的突变体sst1-1和sst1-2（共生硫酸盐转运体）的缺陷基因进行图谱克隆，发现了两个相同基因的等位基因。该基因以结节特异性方式表达，并编码一种与真核硫酸盐转运蛋白同源的蛋白质。该基因的全长cDNA补充了硫酸盐运输缺陷的酵母突变体。因此，该基因被命名为Sst1。Sst1 -1和Sst1 -2突变体在非共生生长条件下生长发育正常，与Sst1的结节特异性表达一致。先前的蛋白质组学研究数据表明，SST1位于莲藕结节的共生体膜上。总之，这些结果表明，SST1将硫酸盐从植物细胞质转运到细胞内根瘤菌，在根瘤菌中，营养物质是蛋白质和辅助因子合成（包括氮酶生物合成）所必需的。这项工作显示了植物硫酸盐转运在SNF中的重要性，以及真核转运基因为此目的的特化。
Symbiotic nitrogen fixation (SNF) by intracellular rhizobia within legume root nodules requires the exchange of nutrients between host plant cells and their resident bacteria. Little is known at the molecular level about plant transporters that mediate such exchanges. Several mutants of the model legume Lotus japonicus have been identified that develop nodules with metabolic defects that cannot fix nitrogen efficiently and exhibit retarded growth under symbiotic conditions. Map-based cloning of defective genes in two such mutants, sst1-1 and sst1-2 (for symbiotic sulfate transporter), revealed two alleles of the same gene. The gene is expressed in a nodule-specific manner and encodes a protein homologous with eukaryotic sulfate transporters. Full-length cDNA of the gene complemented a yeast mutant defective in sulfate transport. Hence, the gene was named Sst1. The sst1-1 and sst1-2 mutants exhibited normal growth and development under nonsymbiotic growth conditions, a result consistent with the nodule-specific expression of Sst1. Data from a previous proteomic study indicate that SST1 is located on the symbiosome membrane in Lotus nodules. Together, these results suggest that SST1 transports sulfate from the plant cell cytoplasm to the intracellular rhizobia, where the nutrient is essential for protein and cofactor synthesis, including nitrogenase biosynthesis. This work shows the importance of plant sulfate transport in SNF and the specialization of a eukaryotic transporter gene for this purpose.