Department of Biology, Stanford University, Stanford, CA 94305, USA.
Science. 2010 Feb 26;327(5969):1126-9. doi: 10.1126/science.1184096.
The nitrogen-fixing symbiosis between Sinorhizobium meliloti and its leguminous host plant Medicago truncatula occurs in a specialized root organ called the nodule. Bacteria that are released into plant cells are surrounded by a unique plant membrane compartment termed a symbiosome. We found that in the symbiosis-defective dnf1 mutant of M. truncatula, bacteroid and symbiosome development are blocked. We identified the DNF1 gene as encoding a subunit of a signal peptidase complex that is highly expressed in nodules. By analyzing data from whole-genome expression analysis, we propose that correct symbiosome development in M. truncatula requires the orderly secretion of protein constituents through coordinated up-regulation of a nodule-specific pathway exemplified by DNF1.
苜蓿中华根瘤菌与其豆科宿主植物紫花苜蓿之间的固氮共生作用发生在一种称为根瘤的专门的根器官中。释放到植物细胞中的细菌被一种称为共生体的独特的植物膜隔室所包围。我们发现，在紫花苜蓿的共生缺陷 dnf1 突变体中，类菌体和共生体的发育被阻断。我们鉴定出 DNF1 基因编码一个信号肽酶复合物的亚基，该复合物在根瘤中高度表达。通过分析全基因组表达分析的数据，我们提出在紫花苜蓿中正确的共生体发育需要通过协调上调以 DNF1 为代表的特定于根瘤的途径，有秩序地分泌蛋白成分。
