Uncommon Descent Serving The Intelligent Design Community

Genome doubling (polyploidy) a key factor in evolution?

Share
Facebook
Twitter
LinkedIn
Flipboard
Print
Email

Well, maybe not as much is this author claims (“Indeed, polyploidy is a major evolutionary force that can lead to adaptation, speciation, and diversification”), but the story is interesting all the same:

From ScienceDaily:

“Genome doubling has shaped the biological world more than any other process,” comments Doug Soltis.

You mean, not Darwinism? Not natural selection? Be careful, you are treading on sacred ground.

“Some might consider this an overstatement, but in the plant world, genome doubling, or polyploidy, rules. It is common in most plant lineages — and it is also crucial in many animal lineages, as vertebrates are the result of two ancient events. It is common in fish, some invertebrate lineages, and we humans are ancient polyploids!”

So, even if polyploidy (duplicate sets of genomes) is the norm rather than unusual, what makes that interesting? One reason is that genome doubling can lead to instant speciation.

As Soltis explains, “If two plants with 12 chromosomes hybridized, you would expect the offspring to have 12 chromosomes, right? What if the offspring had 24 chromosomes? That is genome doubling — every chromosome, every gene duplicated — wow, 2X the genetic material to work with instantaneously!”

In their review, Soltis and colleagues emphasize that polyploidy and the important role it has played, especially in plant evolution, would not have gained the recognition it deserves would it not have been for its staunch proponent, G. L. Stebbins. In the mid-20th century Stebbins synthesized what was known at that time about polyploidy, classifying different types of ploidy, discussing ancient polyploidy events, and investigating hybridizing species and polyploid derivatives. More.

Here’s the abstract:

Polyploidy has long been considered a major force in plant evolution. G. Ledyard Stebbins, Jr., an architect of the Modern Synthesis, elegantly addressed a broad range of topics, from genes to chromosomes to deep phylogeny, but some of his most lasting insights came in the study of polyploidy. Here, we review the immense impact of his work on polyploidy over more than 60 years, from his entrance into this fledgling field in the 1920s until the end of his career. Stebbins and his contemporaries developed a model of polyploid evolution that persisted for nearly half a century. As new perspectives emerged in the 1980s and new genetic tools for addressing key aspects of polyploidy have become available, a new paradigm of polyploidy has replaced much of the Stebbinsian framework. We review that paradigm shift and emphasize those areas in which the ideas of Stebbins continue to propel the field forward, as well as those areas in which the field was held back; we also note new directions that plant geneticists and evolutionists are now exploring in polyploidy research. Perhaps the most important conclusion from recent and ongoing studies of polyploidy is that, following Levin and others, polyploidy may propel a population into a new adaptive sphere given the myriad changes that accompany genome doubling.

File:A small cup of coffee.JPG Look, if it had been that simple, everything would long since have double bubbled out to infinity.

Follow UD News at Twitter!

Comments
Double Your Pleasure: What Exactly Can You Get from Polyploidy? - October 10, 2014 Excerpt: "Stebbins viewed polyploid species as genetically depauperate with limited evolutionary potential. A new polyploidy species was envisioned as forming via a single polyploidization event and would therefore exhibit a high degree of genetic uniformity across individuals. Following this model of formation, an allopolyploid would exhibit no homologous, or segregating, variation, only homeologous (nonsegregating) variation. Furthermore, if a mutation were to arise in the polyploid, its effect would be masked by either the presence of a homeologous locus (in an allotetraploid) or multiple alleles (in an autopolyploid). Although not impossible, the fixation of a new mutation is much slower in a polyploid than in its diploid parents. Stebbins (1971 , p. 127) correctly noted that "...the large amount of gene duplication dilutes the effects of new mutations... polyploids have great difficulty evolving truly new adaptive gene complexes" and that "...chromosome doubling will most often have a retarding effect on evolutionary change via mutation, genetic recombination, and selection." Furthermore, this buffering effect of multiple genomes may extend to the origins of morphological variation in a polyploid (Stebbins, 1950 , 1971 [pp. 147-148]): "Very often, even in complexes on which the basis of phytogeographical evidence must be regarded as hundreds of thousands or even millions of years old, the range of morphological variability encompassed by all of the tetraploids is less than the total range of that found among the diploids...",,, http://www.evolutionnews.org/2014/10/double_your_ple090311.html John Sanford, a leading expert in plant genetics, examines Polyploidy (Gene/Chromosome Duplication) fallacies in Appendix 4 of his book "Genetic Entropy and the mystery of the Genome". "What about polyploidy plants? It has been claimed that since some plants are polyploidy (having double the normal chromosome numbers), this proves that duplication must be beneficial and must increase information. Polyploidy was my special area of study during my Ph.D. thesis. Interestingly, it makes a great deal of difference how a polyploid arises. If somatic (body) cells are treated with the chemical called colchicine, cell division is disrupted , resulting in chromosome doubling - but no new information arises. The plants that result are almost always very stunted, morphologically distorted, and generally sterile. The reason for this should be obvious - the plants must waste twice as much energy to make twice as much DNA, but with no new genetic information! The nucleus is also roughly twice as large, disrupting proper cell shape and cell size. In fact, the plants actually have less information than before, because a great deal of the information which controls gene regulation depends on gene dosage (copy number). Loss of regulatory control is loss of information. This is really the same reason why an extra chromosome causes Down's Syndrome. Thousands of genes become improperly improperly regulated, because of extra genic copies. If somatic polyploidization is consistently deleterious, why are there any polyploidy plants at all - such as potatoes? The reason is that polyploidy can arise by a different process - which is called sexual polyploidization.This happens when a unreduced sperm unites with a unreduced egg. In this special case, all of the information within the two parents is combined into the offspring, and there can be a net gain of information within that single individual. But there is no more total information within the population. the information within the two parents was simply pooled. In such a case we are seeing pooling of information, but not any new information.",,, "in some special cases, the extra level of gene backup within a polyploidy can outweigh the problems of disrupted gene regulation and reduced fertility - and so can result in a type of "net gain". But such a "net gain" is more accurately described as a net reduction in the rate of degeneration." John Sanford - Genetic Entropy & The Mystery of the Genome - pages 191-192 - Dr. John Sanford has been a Cornell University Professor for more that 25 years (being semi-retired since 1998). He received his Ph. D. from the University of Wisconsin in the area of plant breeding and plant genetics.,,, His most significant scientific contributions involved three inventions - the biolistic ("gene gun") process, pathogen-derived resistance, and genetic immunization. Most of the transgenic crops grown in the world today were genetically engineered using the gene gun technology developed by John and his collaborators. (Due to such a stellar record in plant genetics, I take Dr. Sanford's unmatched experimental experience of plants, strictly obeying the principle of Genetic Entropy, with never a violation, to be 'state of the art' for what we can expect for the polyploidy of plants).bornagain77
October 10, 2014
October
10
Oct
10
10
2014
11:37 AM
11
11
37
AM
PST
OT: New Precambrian Fossils Are Not Cambrian Ancestors - October 2, 2014 Excerpt: From the headlines you might think that with the discovery of some new Chinese embryo fossils, the enigma of the Cambrian explosion has been solved. The announcement from Virginia Tech trumpets, "New evidence of ancient multicellular life sets evolutionary timeline back 60 million years." ,,, What's new about these fossils? Nothing. Similar embryos were found in the 1990s by J. Y. Chen and Paul Chien in the same Doushantuo formation, and reported in the peer-reviewed literature (Xiao et al. cite that paper in their references). The story is recounted in both Stephen Meyer's book Darwin's Doubt and in the Illustra film Darwin's Dilemma. The presence of embryos in the Precambrian didn't solve the Cambrian explosion problem then, and it doesn't now. In fact, they make the problem worse, because they show that the Precambrian strata were perfectly capable of preserving transitional forms, had they existed. http://www.evolutionnews.org/2014/10/new_precambrian090171.htmlbornagain77
October 2, 2014
October
10
Oct
2
02
2014
07:05 AM
7
07
05
AM
PST
OT: Neil Tyson’s Final Words On His Quote Fabrications: “My bad” http://thefederalist.com/2014/10/02/neil-tysons-final-words-on-his-quote-fabrications-my-bad/bornagain77
October 2, 2014
October
10
Oct
2
02
2014
04:17 AM
4
04
17
AM
PST
Also of note, whole genome duplications, (WGDs), is the result of cell-mediated processes, not simply accidents as is presupposed in Darwinism's theoretical core. How life changes itself: the Read-Write (RW) genome. - 2013 Excerpt: Research dating back to the 1930s has shown that genetic change is the result of cell-mediated processes, not simply accidents or damage to the DNA. This cell-active view of genome change applies to all scales of DNA sequence variation, from point mutations to large-scale genome rearrangements and whole genome duplications (WGDs). This conceptual change to active cell inscriptions controlling RW genome functions has profound implications for all areas of the life sciences. http://www.ncbi.nlm.nih.gov/pubmed/23876611bornagain77
October 1, 2014
October
10
Oct
1
01
2014
11:25 AM
11
11
25
AM
PST
Whether it is gene doubling or genome doubling or retrotransposons, the issue is the same. How do new proteins arise that are truly unique? Can any form of mutation lead to all the genes/proteins/control elements we see? This is the basic question.jerry
October 1, 2014
October
10
Oct
1
01
2014
11:10 AM
11
11
10
AM
PST
of related note: Peer-Reviewed Research Paper on Plant Biology Favorably Cites Intelligent Design and Challenges Darwinian Evolution - Casey Luskin December 29, 2010 Excerpt: Many of these researchers also raise the question (among others), why — even after inducing literally billions of induced mutations and (further) chromosome rearrangements — all the important mutation breeding programs have come to an end in the Western World instead of eliciting a revolution in plant breeding, either by successive rounds of selective “micromutations” (cumulative selection in the sense of the modern synthesis), or by “larger mutations” … and why the law of recurrent variation is endlessly corroborated by the almost infinite repetition of the spectra of mutant phenotypes in each and any new extensive mutagenesis experiment instead of regularly producing a range of new systematic species… (Wolf-Ekkehard Lönnig, “Mutagenesis in Physalis pubescens L. ssp. floridana: Some Further Research on Dollo’s Law and the Law of Recurrent Variation,” Floriculture and Ornamental Biotechnology Vol. 4 (Special Issue 1): 1-21 (December 2010).) http://www.evolutionnews.org/2010/12/peer-reviewed_research_paper_o042191.html Dr. Wolf-Ekkehard Lönnig, (retired) Senior Scientist (Biology), Max Planck Institute for Plant Breeding Research, Emeritus, Cologne, Germany.bornagain77
October 1, 2014
October
10
Oct
1
01
2014
11:03 AM
11
11
03
AM
PST
You mean, not Darwinism? Not natural selection? Be careful, you are treading on sacred ground. Why would an important role for polyploidization conflict with "Darwinism" as the term is used here? Whole genome duplication is a kind of mutation, after all.wd400
October 1, 2014
October
10
Oct
1
01
2014
09:27 AM
9
09
27
AM
PST
John Sanford, a expert in plant genetics, examines Polyploidy (Gene/Chromosome Duplication) fallacies in Appendix 4 of his book "Genetic Entropy and the mystery of the Genome". "What about polyploidy plants? It has been claimed that since some plants are polyploidy (having double the normal chromosome numbers), this proves that duplication must be beneficial and must increase information. Polyploidy was my special area of study during my Ph.D. thesis. Interestingly, it makes a great deal of difference how a polyploid arises. If somatic (body) cells are treated with the chemical called colchicine, cell division is disrupted , resulting in chromosome doubling - but no new information arises. The plants that result are almost always very stunted, morphologically distorted, and generally sterile. The reason for this should be obvious - the plants must waste twice as much energy to make twice as much DNA, but with no new genetic information! The nucleus is also roughly twice as large, disrupting proper cell shape and cell size. In fact, the plants actually have less information than before, because a great deal of the information which controls gene regulation depends on gene dosage (copy number). Loss of regulatory control is loss of information. This is really the same reason why an extra chromosome causes Down's Syndrome. Thousands of genes become improperly improperly regulated, because of extra genic copies. If somatic polyploidization is consistently deleterious, why are there any polyploidy plants at all - such as potatoes? The reason is that polyploidy can arise by a different process - which is called sexual polyploidization.This happens when a unreduced sperm unites with a unreduced egg. In this special case, all of the information within the two parents is combined into the offspring, and there can be a net gain of information within that single individual. But there is no more total information within the population. the information within the two parents was simply pooled. In such a case we are seeing pooling of information, but not any new information.",,, "in some special cases, the extra level of gene backup within a polyploidy can outweigh the problems of disrupted gene regulation and reduced fertility - and so can result in a type of "net gain". But such a "net gain" is more accurately described as a net reduction in the rate of degeneration." John Sanford - Genetic Entropy & The Mystery of the Genome - pages 191-192 - Dr. John Sanford has been a Cornell University Professor for more that 25 years (being semi-retired since 1998). He received his Ph. D. from the University of Wisconsin in the area of plant breeding and plant genetics.,,, His most significant scientific contributions involved three inventions - the biolistic ("gene gun") process, pathogen-derived resistance, and genetic immunization. Most of the transgenic crops grown in the world today were genetically engineered using the gene gun technology developed by John and his collaborators.bornagain77
October 1, 2014
October
10
Oct
1
01
2014
07:32 AM
7
07
32
AM
PST

Leave a Reply