Calmodulin Interacts With MLO Protein to Regulate Defence Against Mildew in Barley

Nature. 2002 Mar 28;416(6879):447-51. doi: 10.1038/416447a.

Abstract

In plants, defence against specific isolates of a pathogen can be triggered by the presence of a corresponding race-specific resistance gene, whereas resistance of a more broad-spectrum nature can result from recessive, presumably loss-of-regulatory-function, mutations. An example of the latter are mlo mutations in barley, which have been successful in agriculture for the control of powdery mildew fungus (Blumeria graminis f. sp. hordei; Bgh). MLO protein resides in the plasma membrane, has seven transmembrane domains, and is the prototype of a sequence-diversified family unique to plants, reminiscent of the seven-transmembrane receptors in fungi and animals. In animals, these are known as G-protein-coupled receptors and exist in three main families, lacking sequence similarity, that are thought to be an example of molecular convergence. MLO seems to function independently of heterotrimeric G proteins. We have identified a domain in MLO that mediates a Ca2+-dependent interaction with calmodulin in vitro. Loss of calmodulin binding halves the ability of MLO to negatively regulate defence against powdery mildew in vivo. We propose a sensor role for MLO in the modulation of defence reactions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ascomycota / physiology
  • Calcium / metabolism
  • Calmodulin / metabolism
  • Calmodulin / physiology*
  • Cloning, Molecular
  • Gene Expression Regulation, Plant
  • Gene Silencing
  • Genetic Complementation Test
  • Hordeum / genetics
  • Hordeum / microbiology
  • Hordeum / physiology*
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Plant Proteins / physiology*
  • Protein Binding
  • Protein Structure, Tertiary

Substances

  • Calmodulin
  • MLO protein, Hordeum vulgare
  • Plant Proteins
  • Calcium