Inheriting mitochondria
Like most eukaryotes, plants get their mitochondria from one of their parents. Most often it is the maternal line that provides them. But like all systems sometimes the mitochondria from the non-contributing parent make it through. Now a group of international researchers found out that in tobacco (Nicotiana tabacum) paternal mitochondria slip through more often than first thought.
While mitochondria are randomly distributed between the daughter cells during division, when two germ cells fuse together only one set of mitochondria can be found in the resulting zygote, often those of mum. But why the mitochondria of the other parent sometimes slip through is really known. It is estimated that this happens 0.0016% of the time.
Ideal phenotype
As you can imagen studying something that only rarely occurs requires large numbers. This can make the work labour intensive. To avoid this the researchers first developed a line with a reliable mitochondrial-linked phenotype. By deleting the mitochondrial NAD9 gene the researchers created a line which germinated much slower than plants that did contain NAD9. This gave them a good phenotype by which to quickly recognize plants which had inherited their mitochondria from a NAD9 containing parent.
The researchers subsequently fertilized flowers from this slow germinating plants with pollen from normal germinating plants. Germinating 1000 of the resulting seeds they found 5 plants that germinated much faster than their siblings. Analysis of those quickly germinating seedlings showed that they contained mitochondria with NAD9, while their slow germinating siblings did not.
Moreover, the researchers found that not all cells in the NAD9 mitochondria containing plants had only NAD9 containing mitochondria. An extreme example of this was one seedling that had NAD9 containing mitochondria in its roots but not in its shoots. This made the researchers realise that most likely they missed some of the plants that did inherit its paternal NAD9 containing mitochondria, but that it only ended up in a few cells.
Happens more often
To confirm this the researchers developed a more sensitive screening method. Directly testing how much NAD9 was present in the seedlings. Surprisingly the researchers found that when growing the plants at 25°C about 0.18% of the offspring inherited their paternal mitochondria. This changed when the plants were grown at 10°C, then 0.78% inherited their paternal mitochondria. This was due to the fact that more mitochondria end up in pollen developed at colder temperatures.
The researchers made this extra visible in a paternal line that missed one of the genes responsible mitochondria degradation in pollen. 7.34% of offspring of those plants grown at 10°C inherited their paternal mitochondria.
So paternal mitochondria inheritance is not as unusual as was believed. It might even be so that stressful situations, like pollen development at cold temperatures increase the chances of inheriting mitochondria from both parents as a way to increase chances of survival.
Literature
Gonzalez-Duran, E., Liang, Z., Forner, J. et al. High-frequency biparental inheritance of plant mitochondria upon chilling stress and loss of a genome-degrading nuclease. Nat. Plants (2026). https://doi.org/10.1038/s41477-026-02242-7
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