In most flowering plants, mitochondrial DNA is maternally inherited. In Nicotiana tabacum (tobacco), this maternal inheritance pattern is considered very strict, meaning the father normally does not pass on mitochondrial DNA at all.
This maternal inheritance pattern has important consequences. If a mother plant carries a mutation (a genetic defect) in her mitochondrial DNA, that defect is almost always passed on to all of her offspring. In some cases, these mitochondrial mutations can affect how the plant grows and develops.
One example where mitochondrial defects are especially noticeable is in pollen, the male reproductive cells of plants. If the mitochondria do not work well, pollen may fail to develop properly. This can result in a condition called cytoplasmic male sterility (CMS), where a plant is unable to produce functional pollen.
Mitochondrial inheritance and CMS
CMS can actually be useful for plant breeders because it allows an efficient production of hybrid seeds. However, CMS is still a biological defect, as the plant cannot reproduce normally on its own. Since mitochondria are inherited only from the mother, simply crossing a female mutant plant with a healthy male plant does not fix this reproduction defect. Even if the father has perfectly healthy mitochondria, they are usually not passed on to the offspring. The defective mitochondria from the mother continue to dominate.
This raises an intriguing question: What if, under certain conditions, the father could pass on mitochondria? If that were possible, could the reproductive defect be corrected?
But an even more fundamental question comes first: Is it possible at all to achieve paternal mitochondrial inheritance in tobacco?
Inspiration from plastid inheritance studies
In our previous study, we found that it is sometimes possible for fathers to pass on plastid DNA under special conditions — for example, after cold treatment or when using a specific tobacco mutant (dpd1) as the pollen donor. In this new study, we showed that these conditions can also increase the rate of paternal mitochondrial inheritance. Remarkably, the inherited paternal mitochondria can rescue the mitochondrial defect and restore the male fertility (In the image: Left flower – a mutant plant producing nonviable pollen; Right flower – a plant that inherited mitochondria from the father, producing functional pollen and regaining fertility)
Important implications of paternal mitochondrial inheritance
Our findings suggest that paternal transmission of mitochondria may be less rare than scientists previously believed. This has several important implications:
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It may offer a way to rescue harmful mutations
If healthy mitochondria from the father can occasionally be transmitted, they could help compensate for defects in the mother’s mitochondrial DNA. -
It opens the door to mitochondrial “mixing”
If mitochondria from both parents are present, their genetic material could potentially recombine. This could generate new mitochondrial DNA combinations and influence how mitochondrial genomes evolve over time. -
It challenges a long-standing assumption about mitochondrial inheritance
While maternal inheritance remains the dominant rule, it is not as strict as once believed. Even rare exceptions can have major biological and evolutionary consequences.