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Mistletoe differs from all other cellular life in having largely lost the ability to produce fuel


You couldn’t have made this one up:

The cells of all multicellular organisms rely on the organelles called mitochondria to make their biochemical fuel — all multicellular organisms except mistletoes, that is. Not only do their mitochondria produce little if any of this fuel, they’ve lost many of the genes needed to make it. In the few years since botanists discovered this anomaly, scientists worldwide have tried with no more than limited success to figure out how mistletoes pull off this trick …

It could be that something like a catastrophic mutation befell the mistletoes early in their group’s evolution, something that accidentally wiped out their ability to make complex I. “And then mistletoe just managed to cope with what happened,” she said, perhaps because mistletoe’s parasitic lifestyle offered ways to compensate. She is curious about whether additional genetic sequencing might let researchers suss out when the loss happened and whether the plants were already parasitic.

Christie Wilcox, “The Mystery of Mistletoe’s Missing Genes” at Quanta (December 21, 2020)

The trait was only discovered in 2015. It sounds like another example of devolution, actually. A parasitic lifestyle enables a life form to dump complex traits, relying on other life forms to do the job.

See also: Darwin Devolves

I really gotta wonder about the intermediate steps of its "evolution". How does a "semi-parasite" work during the Transition Phase? And what does it GAIN by going Full Parasite? mahuna
The parasitic explanation doesn't work well from either direction. First, mIstletoe isn't a total parasite. It photosynthesizes like other plants, and takes *some* of its nutrition from trees. Second, no other parasite among the huge number of total internal parasites has lost this function. There must be another reason. polistra

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