Germ-line mitochondria exhibit suppressed respiratory activity to support their accurate transmission to the next generation.
Mitochondria are accurately transmitted to the next generation through a female germ cell in most animals. Mitochondria produce most ATP, accompanied by the generation of reactive oxygen species (ROS). A specialized mechanism should be necessary for inherited mitochondria to escape from impairments of mtDNA by ROS. Inherited mitochondria are named germ-line mitochondria, in contrast with somatic ones. We hypothesized that germ-line mitochondria are distinct from somatic ones. The protein profiles of germ-line and somatic mitochondria were compared, using oocytes at two different stages in Xenopus laevis. Some subunits of ATP synthase were at a low level in germ-line mitochondria, which was confirmed immunologically. Ultrastructural histochemistry using 3,3'-diaminobenzidine (DAB) showed that cytochrome c oxidase (COX) activity of germ-line mitochondria was also at a low level. Mitochondria in one oocyte were segregated into germ-line mitochondria and somatic mitochondria, during growth from stage I to VI oocytes. Respiratory activity represented by ATP synthase expression and COX activity was shown to be low during most of the long gametogenetic period. We propose that germ-line mitochondria that exhibit suppressed respiration alleviate production of ROS and enable transmission of accurate mtDNA from generation to generation.
Graduate School of Life Science, University of Hyogo, 3-2-1 Koto, Kamigori, Akou-gun, Hyogo 678-1297, Japan.
Naomi
N
Kogo
Akira
A
Tazaki
Yasuhiro
Y
Kashino
Keisuke
K
Morichika
Hidefumi
H
Orii
Makoto
M
Mochii
Kenji
K
Watanabe
D015100:3,3'-Diaminobenzidine; D000818:Animals; D015153:Blotting, Western; D019069:Cell Respiration / Q000502:physiology; D003576:Electron Transport Complex IV / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D005854:Germ Cells / Q000166:cytology*; D008854:Microscopy, Electron; D008928:Mitochondria / Q000502:physiology* / Q000648:ultrastructure; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014982:Xenopus laevis / Q000196:embryology* / Q000378:metabolism
D017382:Reactive Oxygen Species; D015100:3,3'-Diaminobenzidine; D003576:Electron Transport Complex IV; D025261:Mitochondrial Proton-Translocating ATPases