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
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