Reduced chlorophyll biosynthesis in heterozygous barley magnesium chelatase mutants

Plant Physiol Biochem. 2014 May:78:10-4. doi: 10.1016/j.plaphy.2014.02.004. Epub 2014 Feb 17.

Abstract

Chlorophyll biosynthesis is initiated by magnesium chelatase, an enzyme composed of three proteins, which catalyzes the insertion of Mg2+ into protoporphyrin IX to produce Mg-protoporphyrin IX. In barley (Hordeum vulgare L.) the three proteins are encoded by Xantha-f, Xantha-g and Xantha-h. Two of the gene products, XanH and XanG, belong to the structurally conserved family of AAA+ proteins (ATPases associated with various cellular activities) and form a complex involving six subunits of each protein. The complex functions as an ATP-fueled motor of the magnesium chelatase that uses XanF as substrate, which is the catalytic subunit responsible for the insertion of Mg2+ into protoporphyrin IX. Previous studies have shown that semi-dominant Xantha-h mutations result in non-functional XanH subunits that participate in the formation of inactive AAA complexes. In the present study, we identify severe mutations in the barley mutants xantha-h.38, -h.56 and -h.57. A truncated form of the protein is seen in xantha-h.38, whereas no XanH is detected in xantha-h.56 and -h.57. Heterozygous mutants show a reduction in chlorophyll content by 14-18% suggesting a slight semi-dominance of xantha-h.38, -h.56 and -h.57, which otherwise have been regarded as recessive mutations.

Keywords: AAA; BchI; ChlI; Hordeum vulgare; Mg-chelatase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blotting, Western
  • Chlorophyll / biosynthesis*
  • Genes, Dominant / genetics
  • Heterozygote
  • Hordeum / enzymology
  • Hordeum / genetics*
  • Hordeum / metabolism
  • Lyases / genetics*
  • Lyases / metabolism
  • Mutation*
  • Plant Proteins / genetics*
  • Plant Proteins / metabolism
  • Polymerase Chain Reaction
  • Protein Subunits / genetics
  • Protein Subunits / metabolism

Substances

  • Plant Proteins
  • Protein Subunits
  • Chlorophyll
  • Lyases
  • magnesium chelatase