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Two-Component Signal Transduction Systems of Xanthomonas spp.: A Lesson from Genomics

February 2008 , Volume 21 , Number  2
Pages  151 - 161

Wei Qian,1,2 Zhong-Ji Han,1 and Chaozu He1

1State Key Laboratory of Plant Genomics, Institute of Microbiology, Chinese Academy of Sciences. Beijing 100101, P. R. China; 2National Center for Plant Gene Research, Beijing 100101. P. R. China

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Accepted 26 October 2007.

The two-component signal transduction systems (TCSTSs), consisting of a histidine kinase sensor (HK) and a response regulator (RR), are the dominant molecular mechanisms by which prokaryotes sense and respond to environmental stimuli. Genomes of Xanthomonas generally contain a large repertoire of TCSTS genes (approximately 92 to 121 for each genome), which encode diverse structural groups of HKs and RRs. Among them, although a core set of 70 TCSTS genes (about two-thirds in total) which accumulates point mutations with a slow rate are shared by these genomes, the other genes, especially hybrid HKs, experienced extensive genetic recombination, including genomic rearrangement, gene duplication, addition or deletion, and fusion or fission. The recombinations potentially promote the efficiency and complexity of TCSTSs in regulating gene expression. In addition, our analysis suggests that a co-evolutionary model, rather than a selfish operon model, is the major mechanism for the maintenance and microevolution of TCSTS genes in the genomes of Xanthomonas. Genomic annotation, secondary protein structure prediction, and comparative genomic analyses of TCSTS genes reviewed here provide insights into our understanding of signal networks in these important phytopathogenic bacteria.

Additional keywords:gene regulation.

© 2008 The American Phytopathological Society