Although the genes that determined the abnormal autoimmunity were different in most crosses, the researchers discovered that often only two genes were required to cause the necrotic hybrid response. One of the fatal genes came from the father, the other from the mother. In one case that the researchers studied in more detail, they found that the gene that causes necrosis in hybrids, but not in the parents, is normally used to sense the presence of a pathogen. The scientists emphasize, however, that the hybrids are not the victims of malfunctioning genes: in contrast to many hereditary diseases, the necrosis is not due to each parent carrying a defective copy of the same gene. Rather, there is a destructive interaction between two different genes, each of which evolved differently in the two parents. The genes on their own are harmless or even beneficial, since the parents are healthy. Only the combination of the altered gene variants creates problems. These types of genetic malfunction are often known as Dobzhanshy-Muller incompatibilities, after the two giants of early modern genetics who first studied these necrotic hybrids in fruit flies.
The results of the German-American team challenge the classical definition of a species, according to which ind
|Contact: Professor Dr. Detlef Weigel|