A novel insight into the regulation of light-independent chlorophyll biosynthesis in <Emphasis Type="Italic">Larix decidua</Emphasis> and <Emphasis Type="Italic">Picea abies</Emphasis> seedlings |
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Authors: | Viktor Demko Andrej Pavlovi? Danka Valková L’udmila Slováková Bernhard Grimm Ján Hudák |
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Institution: | (1) Department of Plant Physiology, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovakia;(2) Department of Molecular Biology, Faculty of Natural Sciences, Comenius University, Mlynská dolina, 842 15 Bratislava, Slovakia;(3) Institute of Biology/Plant Physiology, Humboldt University Berlin, Philippstrasse 13, 10115 Berlin, Germany |
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Abstract: | Light-independent chlorophyll (Chl) biosynthesis is a prerequisite for the assembly of photosynthetic pigment–protein complexes
in the dark. Dark-grown Larix decidua Mill. seedlings synthesize Chl only in the early developmental stages and their Chl level rapidly declines during the subsequent
development. Our analysis of the key regulatory steps in Chl biosynthesis revealed that etiolation of initially green dark-grown
larch cotyledons is connected with decreasing content of glutamyl-tRNA reductase and reduced 5-aminolevulinic acid synthesizing
capacity. The level of the Chl precursor protochlorophyllide also declined in the developing larch cotyledons. Although the
genes chlL, chlN and chlB encoding subunits of the light-independent protochlorophyllide oxidoreductase were constitutively expressed in the larch
seedlings, the accumulation of the ChlB subunit was developmentally regulated and ChlB content decreased in the fully developed
cotyledons. The efficiency of chlB RNA-editing was also reduced in the mature dark-grown larch seedlings. In contrast to larch, dark-grown seedlings of Picea abies (L.) Karst. accumulate Chl throughout their whole development and show a different control of ChlB expression. Analysis of
the plastid ultrastructure, photosynthetic proteins by Western blotting and photosynthetic parameters by gas exchange and
Chl fluorescence measurements provide additional experimental proofs for differences between dark and light Chl biosynthesis
in spruce and larch seedlings. |
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Keywords: | Chlorophyll biosynthesis Light-independent protochlorophyllide oxidoreductase Gymnosperms Plastids RNA-editing |
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