GGDEF and EAL proteins play different roles in the control of Sinorhizobium melUoti growth, motility, exopolysaccharide production, and competitive nodulation on host alfalfa  

作　　者：Yiwen Wang Ji Xu Aimin Chen Yanzhang Wang Jiabi Zhu Guanqiao Yu Ling Xu Li Luo 

机构地区：[1]School of Life Science, East China Normal University, Shanghai 200062, China [2]State Key Lab of Plant Molecular Genetics, Institute of Plant Physiology and Ecology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai 200032, China

出　　处：《Acta Biochimica et Biophysica Sinica》2010年第6期410-417,共8页生物化学与生物物理学报（英文版）

基　　金：This work was supported by grants from the National Key Program for Basic Research （2010CB126501）, the Natural Science Foundation of Shanghai （09ZR1436500） and the Knowledge Innovation Program of Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences （2009KIP206） to L.L., and the Excellent Ph.D. Graduate Education Fund of East China Normal University （2009039） to ~.W.

摘　　要：A new bacterial secondary messenger, bis-（3＇,5＇）-cyclic dimeric guanosine monophosphate （c-di-GMP）, is usually synthesized or decomposed by proteins containing GGDEF or glutamate-alanine-leucine （EAL） domain. They often act as cyclase or phosphodiesterase of c-di-GMP and their genes are distributed among almost all bacteria according to known genomic DNA sequences. However, the systematic identification of GGDEF and EAL genes remains unclear in rhizobia, soil bacteria that interact with compatible legumes to form nitrogen-fixing nodules. In this study, 19 putative GGDEF and EAL genes were identified in a model rhizobium, Sinorhizobium meliloti, by bioinformatic analysis （encoding 5 GGDEF proteins, 4 EAL proteins, and 10 GGDEF and EAL double-domain proteins）. Null mutants of 14 genes were constructed through systematic plasmid insertion. AH 14 gene mutants showed deficient growth in minimal medium and defective motility, and 11 gene mutants produced a lot more exopolysaccharide and displayed less competitive nodulation on the host plant, alfalfa. Our results suggested that GGDEF and EAL proteins may play different roles in the control of S. meliloti physiology, although they contain conserved catalytic （GGDEF or EAL） domains. Our finding also implied that c-di-GMP may play an important role in the interactions between this rhizobium and its host plants to establish efficient symbiosis.A new bacterial secondary messenger, bis-（3＇,5＇）-cyclic dimeric guanosine monophosphate （c-di-GMP）, is usually synthesized or decomposed by proteins containing GGDEF or glutamate-alanine-leucine （EAL） domain. They often act as cyclase or phosphodiesterase of c-di-GMP and their genes are distributed among almost all bacteria according to known genomic DNA sequences. However, the systematic identification of GGDEF and EAL genes remains unclear in rhizobia, soil bacteria that interact with compatible legumes to form nitrogen-fixing nodules. In this study, 19 putative GGDEF and EAL genes were identified in a model rhizobium, Sinorhizobium meliloti, by bioinformatic analysis （encoding 5 GGDEF proteins, 4 EAL proteins, and 10 GGDEF and EAL double-domain proteins）. Null mutants of 14 genes were constructed through systematic plasmid insertion. AH 14 gene mutants showed deficient growth in minimal medium and defective motility, and 11 gene mutants produced a lot more exopolysaccharide and displayed less competitive nodulation on the host plant, alfalfa. Our results suggested that GGDEF and EAL proteins may play different roles in the control of S. meliloti physiology, although they contain conserved catalytic （GGDEF or EAL） domains. Our finding also implied that c-di-GMP may play an important role in the interactions between this rhizobium and its host plants to establish efficient symbiosis.

关 键 词：GGDEF domain EAL domain C-DI-GMP competitive nodulation 

分 类 号：Q939.114[生物学—微生物学] TS262.5[轻工技术与工程—发酵工程]