3-Phosphoglycerate dehydrogenase in Mesorhizobioum loti is essential for maintaining symbiotic nitrogen fixation of Lotus japonicus root nodules

Abstract

Mesorhizobium loti is a Gram negative bacterium that induces N 2 -fixing root nodules on the model legume Lotus japonicus. Proteomic analysis in M. loti indicated that 3-phosphoglycerate dehydrogenase (EC. 1.1.1.95, PHGDH) protein content was 2.2 times higher in bacteroids than in cultured bacteria. A M. loti mutant (STM5) with a transposon insertion in the PHGDH gene, mll3875, showed an absolute dependence on serine or glycine in minimal medium for growth. When L. japonicus plants were infected with STM5, the roots formed nodules in numbers comparable to those formed by wild type M. loti; however, the nodules showed very low acetylene reduction activity, and significant starch granule accumulation was observed in the uninfected cells. In such nodules, vast necrosis occurred in the central tissue of the nodules, although bacteroids were detected in the infected cell of the nodules. These data indicate that serine or glycine biosynthesis by PHGDH is important for maintaining symbiosis and nitrogen fixation in L. japonicus nodules.

The National BioResource Project (NBRP) Lotus and Glycine in Japan

“…Detailed information about M. loti ORFs, such as the operon structure, predicted protein domains and orthologous protein groups, is available at RhizoBase ( http://bacteria.kazusa.or.jp/rhizobase/Mesorhizobium/index.html ), a database constructed by the Kazusa DNA Research Institute. The M. loti mutant STM5 that contains an inserted transposon at 738 bp of the 1,602-bp PHGDH (3-phosphoglycerate dehydrogenase) gene plays an important role in the development of an effective symbiosis between M. loti and L. japonicus ( Thapanapongworakul et al 2010 ).…”

The Lotus japonicus Genome

“…The M. loti mutant STM 5 that contains an inserted transposon in the 3-phosphoglycerate dehydrogenase gene played an important role in identifying the molecular basis for effective symbiosis between M. loti and L. japonicus (Thapanapongworakul et al 2010). Shoots of FOX lines were rooted in flat-bottomed test tubes.…”