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Updated: Mar 10, 2026

Single-plant, Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti
20:01

Single-plant, Sterile Microcosms for Nodulation and Growth of the Legume Plant Medicago truncatula with the Rhizobial Symbiont Sinorhizobium meliloti

Published on: October 1, 2013

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Type IV Effector Proteins Involved in the Medicago-Sinorhizobium Symbiosis

Matthew S Nelson1,2, Chan Lan Chun1, Michael J Sadowsky1,3

  • 11 Biotechnology Institute.

Molecular Plant-Microbe Interactions : MPMI
|December 6, 2016
PubMed

Insights

Sinorhizobium bacteria use a type IV secretion system (T4SS) and its effector protein TfeA to initiate symbiosis with Medicago plants. This T4SS influences nodule formation and bacterial competitiveness during this crucial plant-microbe interaction.

Area of Science:

  • Microbiology
  • Plant Science
  • Genetics

Background:

  • The type IV secretion system (T4SS) is crucial for bacterial pathogenesis and symbiosis.
  • Sinorhizobium spp. are important symbionts of legumes, forming nitrogen-fixing nodules.
  • The role of T4SS in Sinorhizobium symbiosis was previously unclear.

Purpose of the Study:

  • To investigate the genetic elements of the T4SS in Sinorhizobium spp.
  • To determine the function of T4SS components, particularly effector proteins, in symbiosis with Medicago truncatula.
  • To elucidate the regulatory mechanisms controlling T4SS gene expression.

Main Methods:

  • Cre reporter assay to validate effector translocation.
  • Sequence analysis to identify regulatory elements like the nod box.
  • Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) to assess gene expression.
  • Generating mutants to study the in planta function of T4SS and TfeA.

Main Results:

  • Identified TfeA as a translocated effector protein in Sinorhizobium meliloti and S. medicae.
  • Discovered a nod box upstream of virG, regulating symbiosis-related genes.
  • Luteolin upregulated the transcription of tfeA and virG.
  • Mutations in T4SS or tfeA reduced nodule formation and competitiveness in Medicago truncatula.

Conclusions:

  • Sinorhizobium spp. utilize a T4SS during the initiation of symbiosis with Medicago spp.
  • The T4SS and its effector TfeA play significant roles in modulating Medicago cells during symbiosis.
  • This study provides evidence for the widespread use of T4SS in rhizobial-legume symbiosis.

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