Uncommon Descent Serving The Intelligent Design Community

Today in horizontal gene transfer: Ferns adapted to low light via HGT

Hornworts/Fay-Wei Li

From ScienceDaily:

During the age of the dinosaurs, the arrival of flowering plants as competitors could have spelled doom for primitive ferns. Instead, ferns diversified and flourished under the new canopy — using a mysterious gene that helped them adapt to low-light environments. Scientists have now pinpointed the curious origins of this gene and determined that it was transferred to ferns from a group of unassuming, mossy plants called hornworts.

If ferns were so “primitive,” how did they manage to do this?

And hornworts? “A hornwort is a flowerless, spore-producing plant – with the spores typically produced in a tapering, horn-like or needle-like capsule which develops from a flattish, green sheet.” It is believed to have parted ways with the ferns about 400 million years ago.


Only one mechanism could explain how the gene hopped from hornworts to ferns so long after the lineages themselves diverged: horizontal gene transfer. But researchers have only just begun to explore how this occurs in plants.

They have only begun because the decline in Darwinism has only recently made it okay to openly look for non-Darwinian mechanisms.

“We’re actually seeing more and more incidence of horizontal gene transfer in plants, but there’s no definite answer as to what mediates it,” Li said.

In the microbial world, bacteria, fungi and viruses have been shown to mediate horizontal gene transfer wherever bits of genetic material get mixed up in different organisms. It’s a messy affair, but it can have powerful evolutionary consequences — gene transfer is how many bacteria learn antibiotic resistance, for example.

Let the record show that he said that HGT, not Darwinian natural selection, “is how many bacteria learn antibiotic resistance.” And keep that in mind when a science mediabot tells you that if you doubt Darwin, you are impeding antibiotic research.

However neochrome was transferred, it seems to have occurred at just the right moment in ferns’ evolutionary history.

Stare at a point in the far distance, okay?

See also: HGT: Gene from bacteria lets beetle feed only on coffee beans

Why horizontal gene transfer is bad news for Darwinism

Here’s the abstract:

Significance: Despite being one of the oldest groups of land plants, the majority of living ferns resulted from a relatively recent diversification following the rise of angiosperms. To exploit fully the new habitats created by angiosperm-dominated ecosystems, ferns had to evolve novel adaptive strategies to cope with the low-light conditions exerted by the angiosperm canopy. Neochrome, an unconventional photoreceptor that allows ferns to “see the light” better, was likely part of the solution. Surprisingly, we discovered that fern neochrome was derived from a bryophyte lineage via horizontal gene transfer (HGT). This finding not only provides the first evidence that a plant-to-plant HGT can have a profound evolutionary impact but also has implications for the evolution of photosensory systems in plants.

Ferns are well known for their shade-dwelling habits. Their ability to thrive under low-light conditions has been linked to the evolution of a novel chimeric photoreceptor—neochrome—that fuses red-sensing phytochrome and blue-sensing phototropin modules into a single gene, thereby optimizing phototropic responses. Despite being implicated in facilitating the diversification of modern ferns, the origin of neochrome has remained a mystery. We present evidence for neochrome in hornworts (a bryophyte lineage) and demonstrate that ferns acquired neochrome from hornworts via horizontal gene transfer (HGT). Fern neochromes are nested within hornwort neochromes in our large-scale phylogenetic reconstructions of phototropin and phytochrome gene families. Divergence date estimates further support the HGT hypothesis, with fern and hornwort neochromes diverging 179 Mya, long after the split between the two plant lineages (at least 400 Mya). By analyzing the draft genome of the hornwort Anthoceros punctatus, we also discovered a previously unidentified phototropin gene that likely represents the ancestral lineage of the neochrome phototropin module. Thus, a neochrome originating in hornworts was transferred horizontally to ferns, where it may have played a significant role in the diversification of modern ferns.– Fay-Wei Li, Juan Carlos Villarreal, Steven Kelly, et al. Horizontal transfer of an adaptive chimeric photoreceptor from bryophytes to ferns. Proceedings of the National Academy of Sciences, April 14, 2014 DOI: 10.5061/dryad.fn2rg

Follow UD News at Twitter!

It is worthwhile keeping in mind that one accusation against an omniscient Creator is that He would be expected to reuse DNA and not reinvent a slightly different mechanism for each new creation, somewhat like we often use identical light switches in buildings of all different sizes, and even sometimes to turn on appliances such as garbage disposals instead of lights. Leaving aside the cheek of telling an omniscient Deity how He should create, it is worthwhile asking what evolutionists would do if they found this Creator actually reusing DNA. The most obvious thing they would do is to call it horizontal gene transfer. AFAICT, there is no testable distinction between horizontal gene transfer and what we might call facilitated horizontal gene transfer. So the data outlined in the OP could be used, fairly, in an argument that, yes indeed, the Creator did reuse His designs, and the argument in the first paragraph above is a poor one. According to the original article in ScienceDaily,
Ferns have a unique life cycle that might lend itself to horizontal gene transfer, he added. Gametophytes, the fern form that produces sex cells, are promiscuous little plants. "They have no protective layer on top, no cuticle," said Kathleen Pryer, an authority on ferns and professor of biology at Duke. "A gametophyte is also a really compact structure, and the sex organs are right there, with lots of contact with other plants that are all competing for light and space. "Easy access to a fern's sperm and eggs could mean foreign genetic material -- like the gene neochrome -- might easily be passed on to the subsequent generation. However neochrome was transferred, it seems to have occurred at just the right moment in ferns' evolutionary history.
That's an interesting and potentially testable theory. Sprinkle some foreign DNA on the gametophytes and see whether it is incorporated into the ferns. If not, perhaps facilitated horizontal gene transfer should be considered as a mechanism in this case. :) Paul Giem
“We’re actually seeing more and more incidence of horizontal gene transfer in plants, but there’s no definite answer as to what mediates it,” Li said.
The metaphysical commitment to materialistic naturalism is remarkable. A more honest statement would be:
We are seeing more and more genes in a pattern of distribution amongst species that cannot be explained by common descent and we have no idea how that is possible.
If ferns were so “primitive,” how did they manage to do this?
Good question. No idea, but eventually science will tell us how ;-) Dionisio

Leave a Reply