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KMID : 0368420190620010027
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Journal of Plant Biology
2019 Volume.62 No. 1 p.27 ~ p.38
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Chlorophyll Degradation and Light-harvesting Complex II Aggregate Formation During Dark-induced Leaf Senescence in Arabidopsis Pheophytinase Mutants
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Yang Young-Nam
Safarova Rana B.
Park So-Yon
Oh Min-Hyuk
Zulfugarov Ismayil S.
Lee Chin-Bum
Tanaka Ayumi
Paek Nam-Chon
Lee Choon-Hwan
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Abstract
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The stay-green mutant of Arabidopsis thaliana, ore10 forms stable light-harvesting complex II (LHCII) aggregates during dark-induced senescence, which showed a single base deletion (G1351) in the coding region of the pheophytinase (PPH) gene. PPH specifically dephytylates the Mg-free chlorophyll (Chl) pigment pheophytin, yielding pheophorbide. In both ore10 and pph-1 mutants, pheophytin a accumulated due to the deficiency of PPH gene, but the amount was relatively smaller than that of degraded Chl, and most of the pheophytin a was bound to the stable LHCII forming aggregates with some other Chl-protein (CP) complexes. Comparison of Chl a/b ratios in thylakoids, aggregates, and LHCII indicated that the suppression of Chl b to Chl a conversion was stronger when Chl b reductase was missing and weak when PPH is missing in the large Chl catabolic complex, which allowed the partial degradation of Chl b. These results suggest that the PPH-dependent pathway is not specific for LHCII, but common for all CP complexes, including LHCII. In PPH-deficient mutants, the degradation of LHCII was suppressed by the formation of aggregates, and some of the remaining CP complexes and pheophytin a were included in the aggregates. Non-included CP complexes were degraded via an unknown mechanism.
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KEYWORD
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Aggregate, Chlorophyll degradation, Chlorophyllprotein complexes, Dark-induced senescence, Light-harvesting
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