Evolution: carnivorous plant origin (Evolution)

by David Turell , Thursday, March 10, 2022, 00:19 (779 days ago) @ David Turell

Still not clear:

https://www.smithsonianmag.com/science-nature/how-carnivorous-plants-evolved-180979697/...

"...carnivorous plants are having another big moment as researchers begin to get answers to one of botany’s great unsolved riddles: How did typically mild-mannered flowering plants evolve into murderous meat-eaters?

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"Quirky though it is, carnivory has evolved repeatedly over the 140 million-plus years that flowering plants have been around. The adaptation arose independently at least 12 times, says Tanya Renner, an evolutionary biologist at Penn State.

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"Today there are some 800 known carnivorous species. Some, like pitcher plants and many sundews, are passive receivers of prey — albeit with ingenious adaptations such as slippery rims and gluey-tipped hairs that help to secure a meal. Others are more active: Some sundews curl inward, nudging prey into the trap’s stickier center, while a few have an outer ring of fast-moving tentacles that hurl victims to their doom. Most sophisticated of all is the Venus flytrap, Dionaea muscipula, with its sensitive trigger hairs and snap-traps that can distinguish the touch of an insect from a falling raindrop or dead leaf and can judge the size of prey and respond accordingly.

"Despite huge differences in shape and form and mode of killing, all traps are modified leaves or parts of leaves. “That means these plants not only get nutrients from a different source but by a different route, primarily through their leaves rather than their roots,” says Renner.

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"Many features of the carnivorous lifestyle have yet to give up their genetic secrets. But studies of two of its grislier elements — digestion and absorption — are revealing how evolution repurposed existing genes, putting some to work in new places and giving others new functions and the odd tweak to suit them better to their new roles. In many cases, plants that evolved carnivory entirely independently have repurposed the same genes. Faced with the problem of consuming flesh, they all hit on the same solution, Albert says. And central to the transformation was the plant’s age-old system of defense.

"Back in the 1970s, researchers recognized that the digestive fluid they found in traps contained enzymes that functioned in very similar ways to many of the chemical weapons that plants wield against harmful bacteria, fungi and hungry herbivorous insects. Initially, it wasn’t clear whether carnivorous plants made the enzymes themselves or if microbes living in their traps did. Since then, botanists have confirmed that carnivorous plants do produce many of those enzymes and have discovered dozens more.

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"The roster of enzymes includes chitinases, which break down the chitin of insect exoskeletons; flesh-dissolving proteases, which break down proteins; and purple acid phosphatase, which enables plants to extract usable phosphorus from their victims’ deconstructed corpses. All played roles in the ubiquitous and ancient defenses of flowering plants. “The genes for those enzymes were repurposed when plants started to eat the things they were originally protecting themselves from,” says Albert. “Chitinases most likely were for defense against fungi, which have chitin in their cell walls.

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"Evolution’s tendency to adopt and adapt existing tools goes beyond digestion. As chitin, proteins and DNA are broken into smaller molecules, the trap must move them from the outside world to the inside of the plant. In ordinary plants, uptake of nutrients is the job of a root, where transporter proteins continually shuttle them from the soil into the plant. “You might not expect to find those proteins working in a leaf,” says Renner.

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"What came as more of a surprise was the discovery that whenever and wherever a new line of carnivores arose, evolution worked on the same genes.

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"All of them, it turned out, had repurposed the same ancient enzymes — matching ones identified previously in the Venus flytrap. Between them, these five species represent three independent lines of carnivores. This was a classic case of convergent evolution, says Albert.

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"As they continue to explore carnivory, researchers are identifying many more enzymes. “But time and time again we’re finding that they have similar functions across distantly related species,” says Renner, who heads a major investigation into the role of co-option in the making of meat-eaters. Yet while that bolsters the idea that carnivorous plants acquired their new digestive skills in much the same way, there’s growing suspicion that the same might not be true for the all-important mechanism that controls the whole operation by switching on the right genes at the right time." (my bold)

Comment: Note the bold. What controlled the 'whole operation' of coordinating new gene functions all at the same time. I cannot imagine this developed stepwise since partial change had no survival advantage. Back to God as the designer.