Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/12/1999
Publication Date: N/A
Technical Abstract: Rhizobium sp. NGR234 nodulates 112 genera of legumes and the non-legume Parasponia andersonii. The genome of NGR234 is divided into three replicons; a 536 kb symbiotic plasmid, a ~ 2 Mb maga-plasmid, and a ~ 3.7 Mb chromosome. Plasmid transfer experiments indicated that most symbiotic genes are carried on the smaller of the two plasmids, pNGR234a. DNA sequence analysis confirmed these findings. Eighteen percent of pNGR234a is made up of insertion and mosaic sequences (IS/MS), suggesting that the genome is plastic. In addition to nodulation (nod)-, nitrogen fixation (nif)-, and fixation (fix) (involved in bacteriod development) -genes that are known to play roles in nodulation and nitrogen fixation, a locus encoding a type three-secretion system (TTSS) was also found. Induction of the TTSS genes is flavonoid-dependent, but occurs later than nodulation genes. Finally, the chromosome carries only a few putative symbiotic genes sand their role in nodulation remains to be demonstrated.