Correlation between mtDNA complexity and mtDNA replication mode in developing cotyledon mitochondria during mung bean seed germination.
The currently accepted model of recombination-dependent replication (RDR) in plant mitochondrial DNA (mtDNA) does not clearly explain how RDR progresses and how highly complex mtDNA develops. This study aimed to investigate the correlation between RDR and mtDNA complexity during mitochondrial development in mung bean (Vigna radiata) seed, and the initiation and processing of RDR in plant mitochondria. Flow cytometry, pulsed-field gel electrophoresis, electron microscopy, real-time PCR and biochemical studies were used in this study. The highly dynamic changes in mtDNA complexity correspond to mtDNA RDR activity throughout mitochondrial development. With in vitro freeze-thaw treatment or prolonged in vivo cold incubation, the mtDNA rosette core disappeared and the rosette structure converted to a much longer linear DNA structure. D-loops, Holliday junctions and putative RDR forks often appeared near the rosette cores. We hypothesize that the rosette core may consist of condensed mtDNA and a replication starting sequence, and play an initial and central role in RDR. The satellite cores in the rosette structure may represent the re-initiation sites of mtDNA RDR in the same parental molecule, thereby forming highly complex and giant mitochondrial molecules, representing the RDR intermediates, in vivo.
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.|Institute of Plant Biology, National Taiwan University, Taipei, 10617, Taiwan.
Ning
N
Cheng
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.
Yih-Shan
YS
Lo
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.
Mohammad Israil
MI
Ansari
Institute of Plant Biology, National Taiwan University, Taipei, 10617, Taiwan.
Kuo-Chieh
KC
Ho
Institute of Plant Biology, National Taiwan University, Taipei, 10617, Taiwan.
Shih-Tong
ST
Jeng
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.
Na-Sheng
NS
Lin
Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.
Hwa
H
Dai
D018548:Cotyledon / Q000235:genetics / Q000254:growth & development*; D004261:DNA Replication / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000648:ultrastructure; D007887:Fabaceae / Q000196:embryology* / Q000235:genetics; D005615:Freezing; D018525:Germination / Q000235:genetics*; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D008954:Models, Biological; D009690:Nucleic Acid Conformation; D011995:Recombination, Genetic / Q000235:genetics; D012639:Seeds / Q000196:embryology* / Q000235:genetics
D004272:DNA, Mitochondrial
in vitro mtDNA replication; mitochondrial development; mtDNA complexity; mtDNA rosette; mung bean (Vigna radiata); plant mitochondrial DNA; recombination-dependent replication; rosette core