Transcription of ENOD8 in Medicago truncatula nodules directs ENOD8 esterase to developing and mature symbiosomes

Mol Plant Microbe Interact. 2008 Apr;21(4):404-10. doi: 10.1094/MPMI-21-4-0404.

Abstract

In Medicago truncatula nodules, the soil bacterium Sinorhizobium meliloti reduces atmospheric dinitrogen into nitrogenous compounds that the legume uses for its own growth. In nitrogen-fixing nodules, each infected cell contains symbiosomes, which include the rhizobial cell, the symbiosome membrane surrounding it, and the matrix between the bacterium and the symbiosome membrane, termed the symbiosome space. Here, we describe the localization of ENOD8, a nodule-specific esterase. The onset of ENOD8 expression occurs at 4 to 5 days postinoculation, before the genes that support the nitrogen fixation capabilities of the nodule. Expression of an ENOD8 promoter-gusA fusion in nodulated hairy roots of composite transformed M. truncatula plants indicated that ENOD8 is expressed from the proximal end of interzone II to III to the proximal end of the nodules. Confocal immunomicroscopy using an ENOD8-specific antibody showed that the ENOD8 protein was detected in the same zones. ENOD8 protein was localized in the symbiosome membrane or symbiosome space around the bacteroids in the infected nodule cells. Immunoblot analysis of fractionated symbiosomes strongly suggested that ENOD8 protein was found in the symbiosome membrane and symbiosome space, but not in the bacteroid. Determining the localization of ENOD8 protein in the symbiosome is a first step in understanding its role in symbiosome membrane and space during nodule formation and function.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Gene Expression Regulation, Plant
  • Immunoblotting
  • Medicago truncatula / genetics*
  • Medicago truncatula / metabolism
  • Medicago truncatula / microbiology
  • Nitrogen Fixation / genetics
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism
  • Plant Roots / genetics
  • Plant Roots / metabolism
  • Plant Roots / microbiology
  • Root Nodules, Plant / genetics*
  • Root Nodules, Plant / metabolism
  • Root Nodules, Plant / microbiology
  • Sinorhizobium meliloti / growth & development
  • Symbiosis / genetics
  • Transcription, Genetic*

Substances

  • ENOD8 protein, Medicago sativa
  • Plant Proteins