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Incomplete maternal transmission of mitochondrial DNA in Drosophila
R Kondo1, Y Satta, E T Matsuura
1Department of Biology, Ochanomizu University, Tokyo, Japan.
Abstract:
The possibility of incomplete maternal transmission of mitochondrial DNA (mtDNA) in Drosophila, previously suggested by the presence of heteroplasmy, was examined by intra- and interspecific backcrosses of Drosophila simulans and its closest relative, Drosophila mauritiana. mtDNAs of offspring in these crosses were characterized by Southern hybridization with two alpha-32P-labeled probes that are specific to paternal mtDNAs. This method could detect as little as 0.03% paternal mtDNA, if present, in a sample. Among 331 lines that had been backcrossed for ten generations, four lines from the interspecific cross D. simulans (female) x D. mauritiana (male) showed clear evidence for paternal leakage of mtDNA. In three of these the maternal type was completely replaced while the fourth was heteroplasmic. Since in this experiment the total number of fertilization is known to be 331 x 10 = 3310, the proportion of paternal mtDNA per fertilization was estimated as about 0.1%. The mechanisms and evolutionary significance for paternal leakage are discussed in light of this finding.
Insights
Mitochondrial DNA (mtDNA) transmission in Drosophila is usually maternal. This study found rare paternal leakage of mtDNA in some offspring, suggesting incomplete maternal inheritance in certain crosses.
Area of Science:
- Genetics
- Evolutionary Biology
- Molecular Biology
Background:
- Mitochondrial DNA (mtDNA) is typically maternally inherited in many species.
- Heteroplasmy, the presence of different mtDNA types within an individual, suggests potential deviations from strict maternal transmission.
- Investigating deviations from maternal inheritance provides insights into mtDNA transmission dynamics and evolution.
Purpose of the Study:
- To investigate the possibility of incomplete maternal transmission of mitochondrial DNA (mtDNA) in Drosophila.
- To determine the frequency and extent of paternal leakage of mtDNA in inter- and intraspecific crosses.
- To explore the mechanisms and evolutionary implications of paternal mtDNA leakage.
Main Methods:
- Intra- and interspecific backcrosses were performed using Drosophila simulans and Drosophila mauritiana.
- Southern hybridization with specific probes was used to detect and quantify paternal mtDNA in offspring.
- The detection limit of the method was established at 0.03% paternal mtDNA.
Main Results:
- Four out of 331 backcrossed lines showed evidence of paternal mtDNA leakage in an interspecific cross (D. simulans female x D. mauritiana male).
- In three lines, the maternal mtDNA type was completely replaced by the paternal type.
- One line remained heteroplasmic, indicating varying degrees of paternal leakage, estimated at approximately 0.1% per fertilization.
Conclusions:
- Paternal leakage of mtDNA can occur in Drosophila, albeit at a low frequency.
- This finding challenges the paradigm of strict maternal inheritance for mtDNA in this species.
- Paternal leakage has potential implications for mtDNA evolution and population genetics.