Sticklebacks have different genes but have the same evolutionary expression

Research shows that when two species of sticklebacks evolved, lost pelvis and body protection, these changes were caused by different genes in each species. This surprised the researchers because they thought that the same gene controls the same changes in two species of fish with close relatives.

Mike Shaprio, lead author of the study and professor at the University of Utah, said: 'We know that in many cases evolution, the same gene is used many times - even in different species. - to create the same anatomical expression. What we found is that different genes can produce the same result.

The study was published online June 4, and will be published in the journal Curent Biology on July 18. This finding raises a new understanding of the evolutionary biodiversity produced in nature. as the evolutionary process reduces spending.

Shapiro said: 'Spending on limbs is a common phenomenon in many animal groups - snakes, whales, manatees and some amphibians. We cannot do genetic research on those animals. Sticklebacks give some insight into what can happen to other animal groups. ' New research focuses on 'converging evolution' when the same trait evolves independently in different species or different populations of the same species. The key question is whether two different species use the same gene or different genes when evolving the same trait. In many cases, the same gene causes two different species to evolve the same trait.

New research shows that different genes can also lead to the evolution of the same traits in two stickleback species. Shapiro said: 'In terms of genetics, we know very little about the mechanisms that create biological diversity. Both of these fish species are increasing diversification, and coincidentally they have the same solution to ecological problems. We found that two species of fish use different genes to accomplish the same purpose, which contrasts with previous studies of sticklebacks.

Shapiro studies how sticklebacks are 2 to 4 inches long that lose the pelvis. Sometimes he made a scientific presentation titled 'Pelvis (pelvis) left the building' - imitating the announcement 'Elvis left the building' decades ago to disperse the crowd of fans. grave after Elvis Presley's performances, rock and roll king.

Shapiro conducted research with three University of Utah biologists: postdoctoral researcher Jaclyn Aldenhoven, graduate student Christopher Cunningham and student Ashley Miller. David Kingsley, a Stanford biologist, is one of the major authors, co-authors include Brian Summers and Sarita Balabhadra of Stanford, and evolutionary biologist Michael A. Bell of Stony Brook University New York.

Different genes reduce the pelvis

Shapiro and colleagues built the first genome map for fish with the name ninespine whale (9 bones), with 9 rough vertebrae on the back and two other bones extending downwards from the pelvis. Pair of 1/4 to 1/2 inch long hip bones evolved from pelvic fins. Pelvic loss and pelvic burns are similar to 'terrestrial animals losing their legs'.

The researchers compared the ninespine stickleback genome to the genome of another species they once studied: threespine sticklebacks, with three larger bones on their backs and usually two large bones attached to the pelvis.

Sticklebacks do not have scales. Instead, it has a protective layer from predatory fish . This protective layer - consisting of 30 flat bones on each side - extends from the back of the head to the tail. In ninespine sticklebacks, there are about 20 copies of the protective bone on each side of the body.

The two on the left are ninespine sticklebacks and the two on the right are threespine sticklebacks.Two children above have pelvic bones, two lower ones have reduced the pelvis.(Photo: Mike Shapiro, University of Utah)

The new study does not identify specific genes responsible for evolutionary changes in ninespine sticklebacks, but instead identifies the location on the chromosomes of these genes.

- The gene responsible for the loss of the pelvis in ninespine sticklebacks is on chromosome 4, but in threespine sticklebacks, the gene responsible for pelvic reduction, called Pitx1, is on chromosomes. number 7.

- The gene responsible for the change in the number of body protectors in ninepine sticklebacks is on chromosome 12. In threespine sticklebacks, the gene responsible for this change is called Eda and lies on the chromosome. 4.

- While the sex indicator gene is on chromosome 12 in ninespine sticklebacks, this gene is on chromosome 19 in threespine sticklebacks.

Shapiro said: 'This is surprising because these two species are quite close. Mammals have not changed sex determination mechanisms for more than 150 million years. '

Glaciers melt, thorny fish 'invade'

There are 6 or maybe 8 species of sticklebacks, all in the Northern Hemisphere. They live in Europe, the North American coast, northern Mexico on the Pacific Ocean, and north from New York on the Atlantic Ocean; throughout the northern coastal regions of Asia. Like salmon, sticklebacks live mainly in the sea and swim upstream to breed. Others live in lakes.

Shapiro said: 'After the ice age glaciers began to melt between 15,000 and 20,000 years ago, sea-going sticklebacks swam upstream to newly formed lakes. Many ninespine and threespine sticklebacks are trapped in lakes, creating evolutionary experiments. They adapt quickly to new freshwater environments. Some changes include the shape and size of the body, the amount of protection on the body, and sometimes, the complete reduction of some major structures like the pelvis'.

In the sea, if threatened by a larger fish, sticklebacks protect themselves by stretching the bones on the back and around the pelvic area . But the need for pelvis changes when the sticklebacks move to the lake area with dragonfly larvae and some insects, but there are no other predatory fish.

Shapiro explains: ' Bone is very effective when you protect yourself from a big fish. But other predators like dragonfly larvae can snatch the spines of sticklebacks, pull them back and 'cup'. They wait for sticklebacks to swim across and capture them. '

So some lake stickleback communities evolved without pelvic bones because those without pelvic bones often had a better chance of survival.

The new study involved mating two developed ninespine sticklebacks without pelvic bones: males from Point MacKenzie, at Cook Inlet near Anchorage, Alaska and females from Fox Holes Lake near Fort Smith, Canada.

Shapiro explains: 'The genetic technique we use makes breeding a necessity. The technique we use to identify the genome or region of the genome controls morphological changes similar to those used by geneticists to track genes responsible for cancer or Other genetic diseases'.

'Applying in vitro fertilization, we resemble two sticklebacks that do not have pelvis, and the result is 120 fry, half of which have pelvis and half are not'.

Using the DNA pattern of the fry 'we have made the first ninespine stickleback genome map , then compare that data with previous studies of threespine sticklebacks. The researchers found that for pelvic bone reduction, number of protections on the body, and sex determination, genes that control these traits in ninespine sticklebacks are quite different from those in fish. threespine thorns.

While new research shows that different genes control the same trait in two closely related stickleback species, in some other cases, the same gene controls the same trait in species with distant relations. Pitx 1 controls the loss of the pelvis in threespine sticklebacks. Eda gene controls the number of body protectors in threespine sticklebacks, and this gene mutates in a human disease including loss of sweat glands, reduced number of teeth, and hair loss.

Refer:
Michael D. Shapiro, Brian R. Summers, Sarita Balabhadra, Jaclyn T. Aldenhoven, Ashley L. Miller, Christopher B. Cunningham, Michael A. Bell, and David M. Kingsley.The Genetic Architecture of Skeletal Convergence and Sex Determination in Ninespine Sticklebacks.Current Biology, 2009;DOI: 10.1016 / j.cub.2009.05.029