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

Reduced chlorophyll biosynthesis in heterozygous barley magnesium chelatase mutants.

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  • 1Carlsberg Laboratory, Gamle Carlsberg Vej 10, 1799 Copenhagen V, Denmark.
  • 2Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), D-06466 Seeland OT Gatersleben, Germany.
  • 3Carlsberg Laboratory, Gamle Carlsberg Vej 10, 1799 Copenhagen V, Denmark. Electronic address:


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.

Copyright © 2014 Elsevier Masson SAS. All rights reserved.


AAA; BchI; ChlI; Hordeum vulgare; Mg-chelatase

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