The roles of a global pH sensor protein ChvG in homologous recombination and mutation of agrobacterium tumefaciens

Abstract

Homologous recombination and mutation are fundamental biological processes. Yet relatively less is known about their regulation. In this study, ChvG, the sensor protein of ChvG-ChvI two-component system, is shown to regulate homologous recombination and mutation processes in A. tumefaciens. ChvG was found to regulate both RecA-dependent and RecA-independent DNA recombination. And it was found that although the mutation frequency was comparable at the exponential phase, most of mutants were one-nucleotide frame-shift mutants for the chvG wild strain, while transposon insertions were prevailing for chvG mutant strain. Under the starvation condition, it was found that the mutation at chvG apparently rendered bacterial cells in a hypermutation state. Interestingly insertion events were predominant for both the wild type strain and the chvG mutant strain under starvation. Our results support the viewpoint that adaptive response to bacteriaa??s ever changing living environment could be on the DNA level too.