Loss of Plastoglobule Kinases ABC1K1 and ABC1K3 Causes Conditional Degreening,Modified Prenyl-Lipids,and Recruitment of the Jasmonic Acid Pathway |
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Authors: | Peter K Lundquist Anton Poliakov Lisa Giacomelli Giulia Friso Mason Appel Ryan P McQuinn Stuart B Krasnoff Elden Rowland Lalit Ponnala Qi Sun Klaas J van Wijk |
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Institution: | aDepartment of Plant Biology, Cornell University, Ithaca, New York 14853;bBoyce Thompson Institute for Plant Science Research, Ithaca, New York 14853;cU.S. Department of Agriculture–Agricultural Research Service, Robert W. Holley Center for Agriculture and Health, Ithaca, New York 14853;dComputational Biology Service Unit, Cornell University, Ithaca, New York 14853 |
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Abstract: | Plastoglobules (PGs) are plastid lipid-protein particles. This study examines the function of PG-localized kinases ABC1K1 and ABC1K3 in Arabidopsis thaliana. Several lines of evidence suggested that ABC1K1 and ABC1K3 form a protein complex. Null mutants for both genes (abc1k1 and abc1k3) and the double mutant (k1 k3) displayed rapid chlorosis upon high light stress. Also, k1 k3 showed a slower, but irreversible, senescence-like phenotype during moderate light stress that was phenocopied by drought and nitrogen limitation, but not cold stress. This senescence-like phenotype involved degradation of the photosystem II core and upregulation of chlorophyll degradation. The senescence-like phenotype was independent of the EXECUTER pathway that mediates genetically controlled cell death from the chloroplast and correlated with increased levels of the singlet oxygen–derived carotenoid β-cyclocitral, a retrograde plastid signal. Total PG volume increased during light stress in wild type and k1 k3 plants, but with different size distributions. Isolated PGs from k1 k3 showed a modified prenyl-lipid composition, suggesting reduced activity of PG-localized tocopherol cyclase (VTE1), and was consistent with loss of carotenoid cleavage dioxygenase 4. Plastid jasmonate biosynthesis enzymes were recruited to the k1 k3
PGs but not wild-type PGs, while pheophytinase, which is involved in chlorophyll degradation, was induced in k1 k3 and not wild-type plants and was localized to PGs. Thus, the ABC1K1/3 complex contributes to PG function in prenyl-lipid metabolism, stress response, and thylakoid remodeling. |
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