(Press-News.org) A new study from SciLifeLab at Uppsala University published in PLOS ONE shows that genes crucial for vision were multiplied in the early stages of vertebrate evolution and acquired distinct functions leading to the sophisticated mechanisms of vertebrate eyes.
One striking feature of vertebrates is the prominent role that vision plays in almost all major animal groups. The vertebrate eye has a unique organization and is known to have arisen at the time of the first vertebrates over 500 million years ago. A new study by the research team led by Xesús Abalo and Dan Larhammar explains how ancient gene duplications have played decisive roles in the evolution of novel functions.
The first step in vision is the response to light by the cone and rod cells in the retina at the back of the eye. Twenty years ago, the first studies of the light receptors, proteins called opsins, in birds indicated that colour vision arose before the dim light black-and-white vision provided by rods. This hypothesis was recently confirmed by detailed studies of opsin genes in a broad range of vertebrate species (David Lagman and Daniel Ocampo Daza in the team of Abalo & Larhammar, BMC Evol. Biol. 2013). The authors found that new opsin genes were generated when the genome of the vertebrate ancestor was doubled twice at the dawn of the vertebrates. These massive gene duplication events resulted in many novel functions, not only for vision but also many other characteristic vertebrate features.
In the new study, David Lagman and co-workers describe evolutionary changes in the first relay step in the vision cascade, mediated by a family of G-proteins called transducins. These trigger the cellular response by activating a critical enzyme. Just like the opsins were multiplied and evolved distinct functions in early vertebrate evolution, also the transducins and their target enzyme were duplicated and diverged to separate functions.
The new study published in PLOS ONE presents a detailed description of the transducins in the retina of the zebrafish, a widely used experimental animal since more than thirty years. This species not only retains all five of the ancestral vertebrate opsins, two of which were lost in mammals including humans, it also displays a greater multiplicity of transducins. Whereas humans have three transducin proteins in cones and three in rods, the zebrafish boasts five cone transducins and four rod transducins thanks to a third genome doubling unique to the group of ray-finned fishes called teleosts.
The authors have explored the fates of all nine transducin genes in the zebrafish retina and report that each duplicate differs from its template in a striking way. First, the zebrafish displays the same distinction as humans between cone versions and rod versions of the transducins. This shows that these two cell types had acquired their characteristic properties already before an early vertebrate ancestor approximately 420 million years ago gave rise to one lineage leading to teleost fishes and one leading to mammals.
Secondly, the teleost-specific duplicates provide novel specialisations. For one such duplicate pair, the two copies have quite different expression levels. For the second pair of transducin genes, one is present in the upper part of the retina and its duplicate is found in the lower part, presumably as a result of very different light intensities hitting the two parts. The one exposed to strong light from above may provide protection from damage. Furthermore, all three pairs of duplicates show differential expression in that one of the copies is also expressed in the pineal gland involved in endocrine regulation of the day-night cycle.
These results show that duplication of genes and genomes has been an important source of new genetic material that has subsequently evolved novel and more specialised functions. Gene duplicates may rapidly adopt altered expression patterns.
Does this mean that zebrafish can see better than humans? Zebrafish have long been known to have the capability to detect ultraviolet light and the retina has a much wider distribution of colour-vision cones than the human eye which has only a narrow cluster of cones in fovea. The new findings add gene specialisations in time, space and amount for duplicated genes. Even if we do not know how a zebrafish sees the world around it, gene duplications clearly allow evolutionary novelties to arise from altered use of spare gene copies, shaping a visual system that let them successfully inhabit a specific environment, just like any other species, including humans.
INFORMATION:
Lagman D, Callado-Pérez A, Franzén IE,Larhammar D, Abalo XM (2015) Transducin Duplicates in the Zebrafish Retina and Pineal Complex: Differential Specialisation after the Teleost Tetraploidisation. PLoS ONE 10(3): e0121330. doi:10.1371/journal.pone.0121330
For more information, please contact:
Dr. Xesús M. Abalo, researcher at the Department of Neuroscience
Mobile: +46 (0)73-6154601, e-mail: xesus.abalo@neuro.uu.se
or
Professor Dan Larhammar, professor in Pharmacology at Department of Neuroscience
Mobile: +46 (0)70-6349214, e-mail: dan.larhammar@neuro.uu.se
Links:
Article in PLOS ONE:
http://www.plosone.org/article/fetchObject.action?uri=info%3Adoi%2F10.1371%2Fjournal.pone.0121330&representation=PDF
Transducin gene evolution: Lagman et al., Genomics 2012:
http://www.ncbi.nlm.nih.gov/pubmed/22814267
Opsin and transducin gene evolution: Lagman & Ocampo Daza et al., BMC Evol. Biol. 2013
http://www.ncbi.nlm.nih.gov/pubmed/24180662
Home page of Dan Larhammar's laboratory:
http://www.neuro.uu.se/research/pharmacology/?languageId=1
Antioxidants provide long-term protection against the chain reactions of free radical processes, in other words, of the molecules that are capable of causing cell damage and generating various diseases. Free radicals harm our body by causing, in the best of cases, ageing and, in the worse, serious diseases. Lettuce is rich in antioxidants, as it contains compounds like phenolic acids, flavonoids, anthocyanins, and vitamins A and C, among other things.
Green, semi-red and red leaves
To conduct this research, which started in 2011 and in which researchers of the UPV/EHU ...
Washington, DC, March 27, 2015 - Patients with Clostridium difficile infection (CDI) are twice as likely to be readmitted to the hospital as patients without the deadly diarrheal infection, according to a study published in the April issue of the American Journal of Infection Control, the official publication of the Association for Professionals in Infection Control and Epidemiology (APIC).
Researchers from the Detroit Medical Center (DMC), a seven-hospital system in southeastern Michigan, conducted a large study to understand the epidemiology of CDI readmissions, analyzing ...
Two scientific studies led by researchers at Sweden's Karolinska Institutet are expected to form the basis of new international recommendations for the treatment of medical abortions and miscarriages. One of the studies, both of which are being published in the journal The Lancet, shows that it is possible to replace the clinical follow-up examinations recommended today with medical abortions that include a home pregnancy test. The other study shows that midwives can safely and effectively treat failed abortions and miscarriages in rural districts of Uganda.
The term ...
Using a simulation model, Swedish researchers have shown that the implementation of Fracture Liaison Services (FLS) could considerably reduce the human and healthcare costs associated with osteoporotic fractures. The results from the model were presented today at the World Congress on Osteoporosis, Osteoarthritis and Musculoskeletal Diseases in Milan.
FLS are coordinated, multi-disciplinary models of care which help ensure that fracture patients are assessed and treated to reduce their risk of subsequent fractures. According to expert opinion and the International Osteoporosis ...
Big data: It's a term we read and hear about often, but is hard to grasp. Computer scientists at Washington University in St. Louis' School of Engineering & Applied Science tackled some big data about an important protein and discovered its connection in human history as well as clues about its role in complex neurological diseases.
Through a novel method of analyzing these big data, Sharlee Climer, PhD, research assistant professor in computer science, and Weixiong Zhang, PhD, professor of computer science and of genetics at the School of Medicine, discovered a region ...
March 27, 2015 (Las Vegas, Nevada) A new study from researchers at NYU Langone's Hospital for Joint Diseases identifies common causes of hospital readmissions following total hip and knee arthoplasty procedures. By finding these common causes, researchers believe quality can be increased and hospital costs decreased.
The study will be presented Friday, March 27, 2015 at the American Academy of Orthopaedic Surgeons Annual Meeting in Las Vegas.
The patients were part of the Bundled Payment for Care Initiative from the Centers for Medicare and Medicaid Services (CMS), ...
LAS VEGAS - Nearly 93 percent of National Football League (NFL) athletes who sustained traumatic injuries to the midfoot returned to competition less than 15 months after injury and with no statistically significant decrease in performance, according to new research from the Perelman School of Medicine at the University of Pennsylvania. The findings, which focus on Lisfranc injuries - characterized by fracture of the midfoot bones and/or disruption of the midfoot ligaments - between 2000-2010, were presented today at the American Academy of Orthopaedic Surgeons (AAOS) annual ...
Young adolescents' judgements on how risky a situation might be are most influenced by what other teenagers think, while most other age groups are more influenced by adults' views, finds new UCL research.
For the study, published in Psychological Science, 563 visitors to the London Science Museum were asked to rate the riskiness of everyday situations such as crossing a road on a red light or taking a shortcut through a dark alley. Ratings were given on a continuous scale from low to high risk, and children (aged 8-11) generally rated situations as more risky than all ...
The official global target of a 2°C temperature rise is 'utterly inadequate' for protecting those at most risk from climate change, says a lead author on the Intergovernmental Panel on Climate Change (IPCC), writing a commentary in the open access journal Climate Change Responses.
The commentary presents a rare inside-view of a two-day discussion at the Lima Conference of the Parties (COP) on the likely consequences of accepting an average global warming target of 2°C versus 1.5°C (measured from pre-industrial times until 2100).
The discussions were part ...
Highlights
For older patients in need of a kidney transplant, rapid transplantation from an older deceased donor is superior to delayed transplantation from a younger donor.
Kidneys from older donors do not have sufficient longevity to provide younger patients with a lifetime of kidney function, but they do have sufficient longevity to provide older patients who have a shorter life expectancy with a lifetime of kidney function.
More than 100,000 people in the United States are waiting for a kidney transplant.
Washington, DC (March 26, 2015) -- A new study highlights ...
