Reduced chlorophyll biosynthesis in heterozygous barley magnesium chelatase mutants

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• 作者：Ilka Braumann^a ; Nils Stein^b ; Mats Hansson^a ; ^{mats.hansson@carlsberglab.dk" class="auth_mail}
• 关键词：AAA ; BchI ; ChlI ; Hordeum vulgare ; Mg-chelatase
• 刊名：Plant Physiology and Biochemistry
• 出版年：May, 2014
• 年：2014
• 卷：78
• 期：Complete
• 页码：10-14
• 全文大小：606 K

文摘

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.