Newly discovered gene sheds light on the evolution of life on Earth

ScienceDaily (July 25, 2011) — A chance discovery of a genetic mutation in wild barley that grows in Israel's Judean Desert, in the course of a doctoral study at the University of Haifa, has led to an international study deciphering evolution of life on land. The study has been published in the journal PNAS.See Also:Plants & AnimalsEndangered PlantsSoil TypesEarth & ClimateWaterEcologyFossils & RuinsCharles DarwinEvolutionReferenceTransgenic plantsSeedbankGlutenAllele frequency

"Life on Earth began in the water, and in order for plants to rise above water to live on land, they had to develop a cuticle membrane that would protect them from uncontrolled evaporation and dehydration. "In our study we discovered a completely new gene that along with other genes contributes to the formation of this cuticle," said Prof. Eviatar Nevo of the Institute of Evolution of the University of Haifa, who took part in the study.

In the course of doctoral research carried out by Guoxiong Chen, which began at the University of Haifa in 2000 under the supervision of Prof. Nevo, the Chinese doctoral student found a mutation of wild barley in the Judean Desert that was significantly smaller than regular wild barley. It was found that this mutation causes an abnormal increase in water loss because of a disruption in the production of the plant's cutin that is secreted from the epidermal cells and is a component in the plant's cuticle that reduces water loss and prevents the plant's dehydration.

Guoxiong Chen has since returned to China and achieved full professorship while continuing his study of the Judean Desert's wild barley for which he enrolled an international team of scholars from China, Japan, Switzerland and Israel. After about eight years of research, this team discovered a new gene that contributes to the production of cutin, which is found in all land plants but is either nonexistent or present in tiny amounts in aquatic plants. Chen called this new gene Eibi1, in honor of his supervisor, Prof. Nevo.

"This is one of the genes that contributed to the actual eventuality of life on land as we know it today. It is a key element in the adaptation process that aquatic plants underwent in order to live on land," explained Prof. Nevo. Besides the evolutionary importance of this new gene, it is also of value in the future enhancement of cereals. According to Prof. Nevo, once we can fully understand the mechanism behind the production of cutin and discover genetic variants of the Eibi1 gene, we will have the ability to enhance the cuticle formation of wheat and barley species so as to make them more resistant to water loss and more durable in the dryer conditions on land. "Genetic enhancement of cultivated plants to make them durable in dry and saline conditions can increase food production around the world," the researcher concluded.

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Butterfly study sheds light on convergent evolution: Single gene controls mimicry across different species

ScienceDaily (July 22, 2011) — For 150 years scientists have been trying to explain convergent evolution. One of the best-known examples of this is how poisonous butterflies from different species evolve to mimic each other's color patterns -- in effect joining forces to warn predators, "Don't eat us," while spreading the cost of this lesson.See Also:Plants & AnimalsEvolutionary BiologyNatureEarth & ClimateEcologyExotic SpeciesFossils & RuinsEvolutionCharles DarwinReferenceDifference between a butterfly and a mothParallel evolutionComputational genomicsTransgenic plants

Now an international team of researchers led by Robert Reed, UC Irvine assistant professor of ecology & evolutionary biology, has solved part of the mystery by identifying a single gene called optix responsible for red wing color patterns in a wide variety of passion vine butterfly species. The result of 10 years of work, the finding is detailed in a paper that appears online July 21 in the journal Science.

"This is our first peek into how mimicry and convergent evolution happen at a genetic level," Reed said. "We discovered that the same gene controls the evolution of red color patterns across remotely related butterflies.

"This is in line with emerging evidence from various animal species that evolution generally is governed by a relatively small number of genes. Out of the tens of thousands in a typical genome, it seems that only a handful tend to drive major evolutionary change over and over again."

The scientists spent several years crossbreeding and raising the delicate butterflies in large netted enclosures in the tropics so they could map the genes controlling color pattern. UCI postdoctoral researcher Riccardo Papa (now an assistant professor at the University of Puerto Rico, Rio Piedras) then perfected a way to analyze the genome map by looking at gene expression in microdissected butterfly wings.

Finding a strong correlation between red color patterns and gene expression in one small region of the genome was the breakthrough that led to discovery of the gene. Population genetics studies in hybrid zones, where different color types of the same species naturally interbreed, confirmed it.

"Biologists have been asking themselves, 'Are there really so few genes that govern evolution?'" Reed said. "This is a beautiful example of how a single gene can control the evolution of complex patterns in nature. Now we want to understand why: What is it about this one gene in particular that makes it so good at driving rapid evolution?"

Papa was co-author on the study. Arnaud Martin, a UCI graduate student in ecology & evolutionary biology, also contributed.

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