title: Slow dark deactivation of Arabidopsis chloroplast ATP synthase caused by a mutation in a nonplastidic SAC domain protein.
abstract: Coupling factor slow recovery (cfs) is a recessive mutant of Arabidopsis with anomalous ATP synthase activation/deactivation characteristics as well as a distinct growth phenotype. The most significant feature of this mutant is that the dark-adapted deactivation of ATP synthase is a very slow relative to the wild type, indicating interference with ATP synthase regulation. Physical mapping of the mutation delimited it to a region in a pair of bacterial artificial chromosome clones. Examination of T-DNA insertion lines of all 34 putative genes located in this region identified two homozygous T-DNA insertion lines of the same gene, At3g59770, possessing phenotypes indistinguishable from the cfs mutant. At3g59770 had been previously identified as suppressor of actin 9 (SAC9), a protein with a SAC domain, a protein-protein interaction module containing two conserved tryptophans known as a WW domain, and an ATP/GTP-binding site motif A. Sequence analysis of cfs revealed a point mutation of G to A resulting in an amino acid substitution from tryptophan to STOP, thereby coding a truncated protein. Real-time-PCR amplification of the gene specific fragments showed that the T-DNA mutants did not have full-length transcripts whereas the cfs mutant transcribed a full-length mutated transcript. Further investigation of SAC9 RNA expression levels in different tissues of wild-type plants by RT-PCR revealed the highest expression in leaves. SAC 9 dysfunction interferes with ATP synthase deactivation, possibly by an alteration in phosphoinositide signaling inducing a stress mimicry response.
authors.affiliation: Department of Plant Biology, University of Illinois, 190 ERML, Urbana, IL 61801, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Gong
authors.forename: Guosheng
authors.initials: G
authors.lastname: Wu
authors.forename: Donald R
authors.initials: DR
authors.lastname: Ort
mesh_terms: D017360:Arabidopsis / Q000201:enzymology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D025222:Chloroplast Proton-Translocating ATPases / Q000378:metabolism*; D002874:Chromosome Mapping; D032461:Chromosomes, Plant; D018506:Gene Expression Regulation, Plant; D009154:Mutation; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics* / Q000378:metabolism*; D010788:Photosynthesis / Q000502:physiology*; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C504532:SAC9 protein, Arabidopsis; D010744:Phosphoric Monoester Hydrolases; D025222:Chloroplast Proton-Translocating ATPases