A strange-looking parasitic plant has thrown off all the machinery of photosynthesis – and yet it has found a way to thrive.
A new analysis of seven Balanophora species found that these crazy plants reduced their plastid genomes, or plastomes – the parts of their cells that oversee photosynthesis – by a factor of 10.
What remains, a mere 16,000 base pairs at most, represents a vestigial relic that is useless for converting sunlight into energy, a process that most plants depend on to survive.
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Instead, Balanophora it takes its cues from the mushroom it so closely resembles, tapping the roots of trees to slurp up their nutrients. Unlike symbiotic mycorrhizal fungi, however, Balanophora he gives absolutely nothing in return; he is a parasite, through and through.
“Balanophora it has lost much of what defines it as a plant, but it has retained enough to function as a parasite,” says botanist Petra Svetlikova of the Okinawa Institute of Science and Technology in Japan.
“It’s a fascinating example of how something so strange can evolve from an ancestor that looked like a normal plant with leaves and a normal root system.”
Balanophora it produces flowers and seeds, but its appearance and behavior are so similar to those of a mushroom that Svetlikova and her colleagues wanted to know more about its evolutionary journey. This similarity is an example of convergent evolution, where two very different, unrelated species develop very similar traits.
The researchers sampled seven species from 12 populations in their hard-to-reach habitats across Taiwan and Japan, and analyzed their genetic code.
They found that Balanophora it has some of the smallest plastomes ever recorded among land plants, with only 14,000 to 16,000 base pairs, compared to the 120,000 to 170,000 base pairs typical of most plants.
Despite this, their tiny remaining plastome is still metabolically active, just not for photosynthesis. This suggests that these fascinating plants do not carry as many extra genes as previously thought, but retain only enough of their plastid machinery to sustain essential metabolism in a parasitic lifestyle.
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The researchers also found that the loss of the plastome occurred in a common ancestor, earlier Balanophora diverging into many separate species.
Balanophora isolated species on islands subsequently evolved the ability to reproduce asexually. In fact, in some species, that is now the only way they can reproduce.
This strategy is rarely seen in obligate systems in plants, and one that researchers say likely boosts the parasite’s chances of establishing new populations on islands, where finding mates – or even suitable habitat – can be difficult.
Earth is the only world on which we know for a fact that life arose. This scarcity suggests that life is fragile – but the tenacity with which organisms adapt and cling to existence is nothing short of amazing.
“Balanophoraceae thus emerge as a fascinating model for reconstructing the evolutionary changes associated with the loss of photosynthesis in land plants,” the researchers write in their paper.
The research was published in New Phytologist.