Simple Genetic Mechanism Could Drive Species Separation

Nature has its ways of keeping species separate. Dogs cannot breed with cats to produce cat-dogs. Although tigers and lions can, ligers and other hybrids such as mule cannot produce offsprings. The genetic basis of species separation has long puzzled scientists. A team of researchers at the French National Institute for Agricultural Research (INRA) in Versailles and University of Nottingham in the UK think that they may have unlocked some of the secrets behind reproductive barriers that isolate one species from another.

The researchers sampled Arabidopsis thaliana strains, the laboratory mouse of the plant world, from Colombia and the Cape Verde Islands. They noted that offspring of the cross between these strains did not fully obey Mendel's classic laws of heredity. Individuals with a specific genetic combination from the two parents were missing.

The team linked the incompatibility between the two strains to a single gene. This gene encodes histidinol phosphate aminotransferase (HPA) an enzyme necessary for the production of the amino acid histidine. HPA is found in chromosome 1 in the Island strain and in chromosomes 1 and 5 in the Colombian strain. The HPA gene became inactivated in chromosome 1 in the Colombian strain. And therefore HPA is carried in two separate chromosomes. Embryos that inherited chromosome 1 from the Colombian strain and chromosome 5 in the Island strain therefore carry no functional HPA gene. This illustrates how evolution of a single gene can rapidly lead to differences within a species.

The paper published by Science is available at http://dx.doi.org/10.1126/science.1165917 For more information, read http://www.international.inra.fr/press/simple_genetic_mechanism_may_be_behind_the_origin_of_species