Open AccessSinorhizobium meliloti 1021 Loss-of-Function Deletion Mutation in chvI and Its Phenotypic Characteristics
Author(s) -
Chunxia Wang,
Jocelyn Kemp,
I. Fonseca,
Raymie C. Equi,
Xiaoyan Sheng,
Trevor C. Charles,
Bruno Sobral
Publication year - 2010
Publication title -
molecular plant-microbe interactions
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.565
H-Index - 153
eISSN - 1943-7706
pISSN - 0894-0282
DOI - 10.1094/mpmi-23-2-0153
Subject(s) - sinorhizobium meliloti , medicago truncatula , mutant , biology , phenotype , gene , flagellum , rhizobia , cell envelope , wild type , mutation , genetics , nod factor , microbiology and biotechnology , open reading frame , effector , function (biology) , symbiosis , bacteria , escherichia coli , peptide sequence
Bacterial two-component regulatory systems (TCS) are common components of complex regulatory networks and cascades. In Sinorhizobium meliloti, the TCS ExoS/ChvI controls exopolysaccharide succinoglycan production and flagellum biosynthesis. Although this system plays a crucial role in establishing the symbiosis between S. meliloti and its host plant, it is not well characterized. Attempts to generate complete loss-of-function mutations in either exoS or chvI in S. meliloti have been unsuccessful; thus, it was previously suggested that exoS or chvI are essential genes for bacterial cell growth. We constructed a chvI mutant by completely deleting the open reading frame encoding this gene. The mutant strain failed to grow on complex medium, exhibited lower tolerance to acidic condition, produced significantly less poly-3-hydroxybutyrate than the wild type, was hypermotile, and exhibited an altered lipopolysaccharide profile. In addition, this mutant was defective in symbiosis with Medicago truncatula and M. sativa (alfalfa), although it induced root hair deformation as efficiently as the wild type. Together, our results demonstrate that ChvI is intimately involved in regulatory networks involving the cell envelope and metabolism; however, its precise role within the regulatory network remains to be determined.