title: Characterization of the structure and DNA complexity of mung bean mitochondrial nucleoids.
abstract: Electron microscopic images of mitochondrial nucleoids isolated from mung bean seedlings revealed a relatively homogeneous population of particles, each consisting of a chromatin-like structure associated with a membrane component. Association of F-actin with mitochondrial nucleoids was also observed. The mitochondrial nucleoid structure identified in situ showed heterogeneous genomic organization. After pulsed-field gel electrophoresis (PFGE), a large proportion of the mitochondrial nucleoid DNA remained in the well, whereas the rest migrated as a 50-200 kb smear zone. This PFGE migration pattern was not affected by high salt, topoisomerase I or latrunculin B treatments; however, the mobility of a fraction of the fast-moving DNA decreased conspicuously following an in-gel ethidium-enhanced UV-irradiation treatment, suggesting that molecules with intricately compact structures were present in the 50-200 kb region. Approximately 70% of the mitochondrial nucleoid DNA molecules examined via electron microscopy were open circles, supercoils, complex forms, and linear molecules with interspersed sigma-shaped structures and/or loops. Increased sensitivity of mtDNA to DNase I was found after mitochondrial nucleoids were pretreated with high salt. This result indicates that some loosely bound or peripheral DNA binding proteins protected the mtDNA from DNase I degradation.
authors.affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, 11509, Republic of China.
authors.forename: Yih-Shan
authors.initials: YS
authors.lastname: Lo
authors.forename: Lin-June
authors.initials: LJ
authors.lastname: Hsiao
authors.forename: Ning
authors.initials: N
authors.lastname: Cheng
authors.forename: Alexandra
authors.initials: A
authors.lastname: Litvinchuk
authors.forename: Hwa
authors.initials: H
authors.lastname: Dai
mesh_terms: D000199:Actins / Q000378:metabolism; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000737:chemistry; D002308:Cardiolipins / Q000378:metabolism; D018548:Cotyledon / Q000235:genetics* / Q000648:ultrastructure; D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000378:metabolism / Q000648:ultrastructure*; D015180:Electrophoresis, Gel, Two-Dimensional; D008854:Microscopy, Electron; D051336:Mitochondrial Membranes / Q000378:metabolism; D009690:Nucleic Acid Conformation; D027805:Phaseolus / Q000235:genetics* / Q000648:ultrastructure; D036226:Seedlings / Q000235:genetics* / Q000648:ultrastructure; D012639:Seeds / Q000235:genetics* / Q000648:ultrastructure; D012965:Sodium Chloride / Q000737:chemistry; D053778:Thiazolidines / Q000737:chemistry
chemical_list: D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002308:Cardiolipins; D004272:DNA, Mitochondrial; D053778:Thiazolidines; D012965:Sodium Chloride; D004264:DNA Topoisomerases, Type I; C037068:latrunculin B