Mechanisms of Gene Regulation
Park, So-Yon , Paek, Nam-Chon .
STAYGREEN Regulates Chlorophyll Degradation by Interacting with Light-harvesting Chlorophyll-binding Protein during Leaf Senescence.
In higher plants, loss of leaf green color results from chlorophyll (Chl) degradation in the chloroplasts, but little is known about how Chl catabolism is tightly regulated throughout development. Using the staygreen (sgr) mutant in rice (Oryza sativa L.) which maintains leaf greenness during senescence, we identified OsSGR with a map-based cloning approach. OsSGR is a senescence-associated gene encoding a novel chloroplast protein. Transgenic rice overexpressing OsSGR produces yellowish-brown leaves and Arabidopsis pheophorbide a oxygenase-impaired mutants exhibiting a stay-green phenotype during dark-induced, detached leaf senescence have reduced expression of AtSGR duplicate genes, indicating that SGR regulates Chl breakdown at the transcriptional level. We show that leaf stay-greenness of the rice sgr mutant is associated with a failure in the destabilization of the light-harvesting Chl-binding protein (LHCP) complexes of the thylakoid membranes, which is a prerequisite event for the degradation of Chls and LHCPs during senescence. Transient overexpression of OsSGR in Nicotiana benthamiana and an in vivo pull-down assay show that SGR interacts with LHCPII. It indicates that the SGR-LHCPII complexes are formed on the stromal side of the thylakoid membranes. Thus, we propose that in senescing leaves, SGR regulates Chl degradation by triggering the LHCPII disassembly through direct interaction, leading to the degradation of Chls and Chl-free LHCPII by catabolic enzymes and proteases, respectively.
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1 - Seoul National University, Department of Plant Science
2 - Seoul National University, Department of Plant Science, San 56-1 Sillim-dong Gwanag-gu, Seoul, 151-921, Korea
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM