Isolation and symbiotic characterization of transposon Tn5-induced arginine auxotrophs of Sinorhizobium meliloti

Anvita Kumar, Neeraj Vij, Gursharn S. Randhawa

Research output: Contribution to journalArticle

Abstract

Seventeen arginine auxotrophic mutants of Sinorhizobium meliloti Rmd201 were isolated by random transposon Tn5 mutagenesis using Tn5 delivery vector pGS9. Based on intermediate feeding studies, these mutants were designated as argA/argB/argC/argD/argE (ornithine auxotrophs), argF/argI, argG and argH mutants. The ornithine auxotrophs induced ineffective nodules whereas all other arginine auxotrophs induced fully effective nodules on alfalfa plants. In comparison to the parental strain induced nodule, only a few nodule cells infected with rhizobia were seen in the nitrogen fixation zone of the nodule induced by the ornithine auxotroph. TEM studies showed that the bacteroids in the nitrogen fixation zone of ornithine auxotroph induced nodule were mostly spherical or oval unlike the elongated bacteroids in the nitrogen fixation zone of the parental strain induced nodule. These results indicate that ornithine or an intermediate of ornithine biosynthesis, or a chemical factor derived from one of these compounds is required for the normal development of nitrogen fixation zone and transformation of rhizobial bacteria into bacteroids during symbiosis of S. meliloti with alfalfa plants.

Original languageEnglish (US)
Pages (from-to)1198-1204
Number of pages7
JournalIndian Journal of Experimental Biology
Volume41
Issue number10
StatePublished - Oct 1 2003

Keywords

  • Arginine biosynthesis
  • Legume
  • Nitrogen fixation
  • Ornithine and transposon mutagenesis
  • Rhizobium
  • Sinorhizobium

ASJC Scopus subject areas

  • Bioengineering

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