I mentioned in my previous entry the sense of transcendence I feel when I observe the green light passing through a tree’s leaves. My neighborhood woods on Princeton Ridge is full of tall trees, including beeches which are my favorite arboreal species. Part of that sense of wonder stems (har) from my knowledge of the inter-relatedness of the tree and myself, my lack of chlorophyll notwithstanding.
John Stiller of East Carolina University contends that we humans are more closely akin to plants than we are to fungi. The following article from ABC Science (that’s the Australian Broadcasting Corporation) outlines some of the reasons that Stiller thinks we need to move beyond molecular sequence-based phylogenetics when comparing plants and animals
As a former botany major and current aficionado of flower pornography, I feel vindicated that someone acknowledges the kissing cousin relationship between the beech trees and me…not that I hug them or anything.
Plants and animals may be long-lost kin by Jennifer Viegas.
Plants and animals may occupy distinct branches on the tree of life, but they could be more alike than we think.
In fact, green plants and animals enjoy a relatively close evolutionary relationship that has been obscured by a narrow focus on DNA sequences to find relatedness, says biologist Associate Professor John Stiller of East Carolina University.
Plants, fungi and animals are eukaryotes, organisms distinguished by their advanced cellular machinery.
But some eukaryotes, most notably the fungi, have long been considered more closely related to animals than plants.
Stiller’s theory suggests a shake-up. He says organisms such as fungi should be given a demotion and placed further from animals on the tree. Meanwhile, green plants should get a leg-up.
In a new paper in the latest issue of the journal Trends in Plant Science, Stiller outlines the evidence.
He says plants and animals have at least five features in common that could not have emerged independently.
“In both green plants and animals, cell cycles are controlled by master switches,” he says. “These function, and malfunction, similarly in both groups.”
As an example of a shared malfunction, Stiller pointed out that both groups suffer from cancerous growths consisting of rapidly diving cells that grow unchecked.
“The difference is that plants can often simply drop the growth in the way that they drop off their leaves, but humans and animals don’t possess that ability,” he says.
RNA in both
Another attribute shared by plants and animals, according to Stiller, is the way the genetic material RNA operates in both groups.
In both plants and animals, RNA acts as an intermediary between DNA and the protein it codes for. The enzymes that put RNA to work in a cell are similar in plants and animals, but not present in fungi or other organisms, he says.
And like animals, plants have an immune system. For the latter, Stiller argues that certain proteins and genes, which are not present in other organisms, help plants and animals defend themselves against invading viruses and bacteria.
Finally, and possibly most intriguingly, Stiller sees strong parallels between plant neurobiology and animal nervous systems.
“Plants obviously do not have actual nerves and brains, but electrical signals do allow plants to sense and to signal,” he says. “Some of the proteins involved in this process are the same in both groups.”
The history of plants
Professor Brent Mishler is a biologist at the University of California Berkeley and leader of The Green Tree of Life project, whose primary goal is to trace the lineage of green plants.
“It is true we don’t have a firm idea of the closest relative of green plants,” he says.
“But the green plant-animal hypothesis defended [by Stiller] is quite unusual and will take a compelling analysis to get people to believe it.”
Note: This is something of a birthday card for a friend who has a fascination for certain green gemstones. An artisan’s inspiration that is derived from “light through the leaves” may be due to “photosynthesis envy!”