Adaptive gains through repeated gene loss: parallel evolution of cyanogenesis polymorphisms in the genus Trifolium (Fabaceae)

Variation in cyanogenesis (hydrogen cyanide release following tissue damage) was first noted in populations of white clover more than a century ago, and subsequent decades of research have established this system as a classic example of an adaptive chemical defence polymorphism. Here, we document polymorphisms for cyanogenic components in several relatives of white clover, and we determine the molecular basis of this trans-specific adaptive variation. One hundred and thirty-nine plants, representing 13 of the 14 species within Trifolium section Trifoliastrum , plus additional species across the genus, were assayed for cyanogenic components (cyanogenic glucosides and their hydrolysing enzyme, linamarase) and for the presence of underlying cyanogenesis genes ( CYP79D15 and Li , respectively). One or both cyanogenic components were detected in seven species, all within section Trifoliastrum ; polymorphisms for the presence/absence (PA) of components were detected in six species. In a pattern that parallels our previous findings for white clover, all observed biochemical polymorphisms correspond to gene PA polymorphisms at CYP79D15 and Li . Relationships of DNA sequence haplotypes at the cyanogenesis loci and flanking genomic regions suggest independent evolution of gene deletions within species. This study thus provides evidence for the parallel evolution of adaptive biochemical polymorphisms through recurrent gene deletions in multiple species.

Research on animal blood groups and biochemical polymorphisms at Onderstepoort (1956-1990) : historical article

The introduction and wide use of artificial insemination in cattle in the 1950s led to a need for accurate parentage identification. Blood group determination by means of the newly emerging scientific discipline called immunogenetics provided the answer. A blood group laboratory was consequently established at Onderstepoort in 1956, initially concentrating on the production of blood typing reagents. Once established the technology was also applied to studies on a variety of problems in various animals as summarised in this paper. Investigations include zygosity in cattle twins, blood transfusion in domestic animals, breed relationships, genetic polymorphisms and the identification of useful genetic markers for production and disease parameters in breeding programmes.