Kim, Minsoo , Lee, Ung , Vierling, Elizabeth .
A dominant HSP101 mutation is suppressed by mutations in an MTERF-related protein.
HSP101 is a hexameric AAA+ protein in the ClpB/Hsp100 chaperone protein family and is required for acquired thermotolerance in plants and other organisms. The protein has two ATP-binding domains and exhibits ATP-dependent protein remodeling activity necessary for its stress-protective function. We identified a dominant negative allele of Arabidopsis HSP101, hot1-4, which is hypersensitive to heat. The hot1-4 allele has a mutation in a coiled-coil domain, which is unique in the ClpB/Hsp100 family proteins. To search for factors that interact with HSP101, we screened for extragenic suppressors of hot1-4 in an M2 population of EMS mutagenized hot1-4 seeds. One suppressor, shot1 (SHOT: suppressor of hot1-4 1), encodes a mitochondrial transcription termination factor-related protein (MTERF). The MTERF family includes diverse proteins in metazoans and plants (including 36 members in Arabidopsis), about which there is limited functional data. Both the shot1-1 missense mutant (G105D) and the shot1-2 knock out mutant (T-DNA insertion) have a short hypocotyl phenotype and suppress the hot1-4 heat-hypersensitive phenotype. Mature shot1-2 plants are smaller than WT or shot1-1 plants. A SHOT1-GFP fusion protein localizes to both mitochondria and chloroplasts in transgenic plants, but not to the cytosol where HSP101 resides. These data indicate that the SHOT1 protein does not interact directly with HSP101, but rather suppresses the hot1-4 phenotype by an indirect mechanism. Further study of the function of SHOT1 and the mechanism by which it suppresses hot1-4 heat-hypersensitivity are in progress.
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1 - The University of Arizona, Plant Sciences, 1140 E. South Campus Drive, Forbes Building, Room 303, Tucson, AZ, 85721-0036, USA
2 - The University of Arizona, Biochemistry and Molecular Biophysics
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM