title: Actin in mung bean mitochondria and implications for its function.
abstract: Here, a large fraction of plant mitochondrial actin was found to be resistant to protease and high-salt treatments, suggesting it was protected by mitochondrial membranes. A portion of this actin became sensitive to protease or high-salt treatment after removal of the mitochondrial outer membrane, indicating that some actin is located inside the mitochondrial outer membrane. The import of an actin-green fluorescent protein (GFP) fusion protein into the mitochondria in a transgenic plant, actin:GFP, was visualized in living cells and demonstrated by flow cytometry and immunoblot analyses. Polymerized actin was found in mitochondria of actin:GFP plants and in mung bean (Vigna radiata). Notably, actin associated with mitochondria purified from early-developing cotyledons during seed germination was sensitive to high-salt and protease treatments. With cotyledon ageing, mitochondrial actin became more resistant to both treatments. The progressive import of actin into cotyledon mitochondria appeared to occur in concert with the conversion of quiescent mitochondria into active forms during seed germination. The binding of actin to mitochondrial DNA (mtDNA) was demonstrated by liquid chromatography-tandem mass spectrometry analysis. Porin and ADP/ATP carrier proteins were also found in mtDNA-protein complexes. Treatment with an actin depolymerization reagent reduced the mitochondrial membrane potential and triggered the release of cytochrome C. The potential function of mitochondrial actin and a possible actin import pathway are discussed.
authors: Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan 11529, Republic of China.
authors: Yih-Shan
authors: YS
authors: Lo
authors: Ning
authors: N
authors: Cheng
authors: Lin-June
authors: LJ
authors: Hsiao
authors: Arunachalam
authors: A
authors: Annamalai
authors: Guang-Yuh
authors: GY
authors: Jauh
authors: Tuan-Nan
authors: TN
authors: Wen
authors: Hwa
authors: H
authors: Dai
authors: Kwen-Sheng
authors: KS
authors: Chiang
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D018548:Cotyledon / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D045304:Cytochromes c / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000235:genetics; D018525:Germination / Q000187:drug effects; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D009698:Nucleoproteins / Q000378:metabolism; D010447:Peptide Hydrolases / Q000494:pharmacology; D027805:Phaseolus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D018272:Porins / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D021381:Protein Transport; D011993:Recombinant Fusion Proteins; D036226:Seedlings / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D012639:Seeds / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000199:Actins; D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; D009698:Nucleoproteins; D018272:Porins; D011993:Recombinant Fusion Proteins; D011189:Potassium Chloride; D045304:Cytochromes c; D010447:Peptide Hydrolases