What'sNEW
| 10 Feb 2025 |
What'sNEW about HGT
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Plants acquire essential genes by horizontal gene transfer (HGT) from bacteria, as two more research projects reveal. With examples piling up, it looks like this is how life makes macroevolutionary advances. (If evolution can make major advances without HGT, where are the convincing examples?)
 "Discovery of bifunctional diterpene cyclases/synthases in bacteria supports a bacterial origin for the plant terpene synthase gene family," by Xinlu Chen et al, doi:10.1093/hr/uhae221, Horticulture Research, 03 Aug 2024; and "Ancient Bacterial Genes Linked to Plant Hormone Biosynthesis," Chinese Academy of Sciences via Newswise, 19 Feb 2025.
"These findings strongly suggest that the ancestral TPS in plants originated from a bacterial DCS gene fusion."
"GRAS transcription factors regulate cell division planes in moss overriding the default rule," by Masaki Ishikawa et al, doi:10.1073/pnas.2210632120, PNAS, 20 Jan 2025.
"A gene encoding a GRAS transcription factor was transferred from soil bacteria to plants, and its descendent genes now regulate formative cell divisions in flowering plants. ...We propose that the acquisition of GRAS genes contributed to the genetic regulatory networks controlling cell division orientation in the ancestor of land plants, and this gene family then underwent expansion and adaptation in flowering plant and moss lineages to specify body plans."
 Thanks, Google Alerts.
 Viruses... has links to thousands of examples of HGT across all domains of life.
The world into which you wish to take us is really too fantastic. That's how a journalist reacted to Pasteur's claim that there are germs in the air, and they do not arise by spontaneous generation.
Louis Pasteur's Relentless Hunt for Germs Floating in the Air, by Carl Zimmer, The New York Times, 17 Feb 2025
The RNA World has lots about modern theories of spontaneous generation.
Louis Pasteur: a brief introduction.
In a brief paper, Chandra Wickramasinghe and Jayant Narlikar remind us of evidence for life from space.
"Life Arriving from Space: Theory and Proof," by N.C. Wickramasinghe1 and J.V. Narlikar, ISSN (O) 2795-8639, Current Science [local pdf], online 08 Feb 2025.
An Atmospheric Test of Cometary Panspermia discusses sample return from the high atmosphere.
Comet Rendezvous has updates about sample return from interplanetary space.
Chandra Wickramasinghe has an introductory essay and many updates.
| 10 Feb 2025 |
What'sNEW about HGT
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Fungal accessory chromosomes can be horizontally transferred, representing a significant horizontal gene transfer (HGT) event, often encompassing hundreds of genes and, in addition, non-genic elements. "Accessory chromosomes are nonessential, linear chromosomes found in some but not all members of a population." They are characterized by a peculiar codon bias which can help identify other, previously unsuspected horizontal transfers of these chromosomes. Also, they "may encode the machinery required for their own horizontal transmission...." In new research, an international team has thus expanded the known extent of horizontal chromosome transfer (HCT) among fungi. The article, available by Open Access, has useful background and references about HGT.
"Horizontal transfer of accessory chromosomes in fungi - a regulated process for exchange of genetic material?" by Habig, M., Patneedi, S.K., Stam, R. et al, Nature (also: epdf), 10 Feb 2025.
The transfer of whole chromosomes among fungi was already known, but almost ignored for its implications. In a single transfer, hundreds of genes may be delivered to species lacking them. This would be a wholesale example of how evolution by cosmic ancestry works.
Viruses... has links to more than a thousand examples of HGT benefitting eukaryotes.
| 07 Feb 2025 |
What'sNEW about HGT
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...a large exogenous bacterial chromosome placed in a eukaryotic context spontaneously adopts eukaryotic chromatin features....
French specialists in genomics and related fields observe this, following experiments introducing bacterial DNA into yeast cells. Perhaps the acquisition of diverse sequences very long ago led to eukaryotic chromatin compartmentalization? The whole subject of eukaryotic DNA supplied by HGT is waiting for exploration.
"Sequence-dependent activity and compartmentalization of foreign DNA in a eukaryotic nucleus," by Léa Meneu, Christophe Chapard et al, doi:10.1126/science.adm9466; and "Relating DNA sequence, organization, and function" [commentary], by Geoffrey Fudenberg and Vijay Ramani, Science, 07 Feb 2025.
Viruses... has a primer and links about HGT from bacteria to eukaryotes.
| 04 Feb 2025 |
What'sNEW about HGT
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...multiple independent events of microbe-to-beetle HGT and specialized symbioses drove convergent evolutionary innovations in approximately 21,000 and 13,500 leaf beetle species, respectively.
This statement comes from an international consortium including veteran entomologists and evolutionary biologists. Their new report makes clear that HGT is a frequent contributor to evolutionary advances in these eukaryotes.
"Symbiosis and horizontal gene transfer promote herbivory in the megadiverse leaf beetles," by Roy Kirsch et al, doi:10.1016/j.cub.2024.12.028; and "Insect herbivory..." [commentary], by Noah K. Whiteman, Current Biology, 03 Feb 2025.
Thanks, Google Alerts.
...among the most compelling detections were amino acids – 14 of the 20 that life on Earth uses to make proteins – and all five nucleobases that life on Earth uses to store and transmit genetic instructions....
This comment comes from one of two large interdisciplinary teams who have analysed samples returned from asteroid Bennu. Fifty years ago, all of the organics would have been thought incredible, but this surprise has been gradually accepted and explained. Now they are considered to be ingredients for the Earthly origin of life, a concept I call pseudo-panspermia. With my opposite gestalt, I suspect that these life-related molecules actually came from life — the simplest way to explain them. I would be surprised if no signs of life were found in space.
The other team (McCoy et al.) was focussed on the minerals in the samples, which must have precipitated from a watery brine on Bennu's parent body. The evidence for liquid water in the asteroids moons of our solar system is another ongoing surprise that also looks favorable for panspermia. Analysis of the valuable Bennu samples is not complete.
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Bennu's valine exhibits life's chiralty (Glavin et al.)
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"Abundant ammonia and nitrogen-rich soluble organic matter in samples from asteroid (101955) Bennu," by Glavin, D.P., Dworkin, J.P., Alexander, C.M.O. et al, doi:10.1038/s41550-024-02472-9, Nature Astronomy, 29 Jan 2025.
"An evaporite sequence from ancient brine recorded in Bennu samples," by McCoy, T.J., Russell, S.S., Zega, T.J. et al, doi:10.1038/s41586-024-08495-6, Nature, 29 Jan 2025; and commentary:
"NASA's Asteroid Bennu Sample Reveals Mix of Life's Ingredients," by Jessica Taveau, NASA, 29 Jan 2025.
"Bennu asteroid...," by Timothy J McCoy and Sara Russell, The Conversation and Smithsonian, 29 Jan 2025.
"Lurking Inside an Asteroid: Life's Ingredients," by Carl Zimmer, The New York Times, 29 Jan 2025.
"Asteroid Bennu contains salts from ancient brine," by Yasuhito Sekine, Nature, 29 Jan 2025.
"Are we all aliens?...," by Marcia Dunn, Phys.Org, 01 Feb 2025.
Thanks for alerts, Patsy Welch and Kenneth Augustyn.
09 Oct 2020: background on the mission to Bennu.
Comet Rendezvous has discussion and updates (search for "Bennu").
Comets: The Delivery System has background and related discussion.
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