Gray K M, Pearson J P, Downie J A, Boboye B E, Greenberg E P
Department of Microbiology, University of Iowa, Iowa City 52242, USA.
J Bacteriol. 1996 Jan;178(2):372-6. doi: 10.1128/jb.178.2.372-376.1996.
The Sym plasmid pRL1JI encodes functions for the formation of nitrogen-fixing pea root nodules by Rhizobium leguminosarum. Some of the nodulation genes are involved in recognition of chemical signals produced by the plant root, and others are required for production of chemical signals recognized by the plant. pRL1JI also contains a regulatory gene, rhiR, that is homologous to luxR, the transcriptional activator of luminescence genes in Vibrio fischeri. LuxR requires a signal compound, an autoinducer, for its activity. We have identified an R. leguminosarum autoinducer that, together with RhiR, is required to activate both the rhizosphere-expressed rhiABC operon and a growth-inhibiting function encoded by pRL1JI. This intercellular signal is an N-acylated homoserine lactone structurally related to the V. fischeri and other autoinducers. These findings indicate a new level of intercellular communication in root nodule formation.
共生质粒pRL1JI编码了豆科根瘤菌形成固氮豌豆根瘤的功能。一些结瘤基因参与识别植物根产生的化学信号，而其他基因则是产生被植物识别的化学信号所必需的。pRL1JI还包含一个调控基因rhiR，它与费氏弧菌中发光基因的转录激活因子luxR同源。LuxR的活性需要一种信号化合物——自诱导物。我们已经鉴定出一种豆科根瘤菌自诱导物，它与RhiR一起，是激活根际表达的rhiABC操纵子和pRL1JI编码的生长抑制功能所必需的。这种细胞间信号是一种N-酰化高丝氨酸内酯，在结构上与费氏弧菌及其他自诱导物相关。这些发现表明在根瘤形成过程中细胞间通讯有了新的层面。
