Properties and natural occurrence of maternal-effect selfish genes ('Medea' factors) in the red flour beetle, tribolium castaneum

Maternally acting selfish genes, termed 'Medea' factors, were found to be widespread in wild populations of Tribolium castaneum collected in Europe, North and South America, Africa and south-east Asia, but were rare or absent in populations from Australia and the Indian subcontinent. We detected at least four distinct genetic loci in at least two different linkage groups that exhibit the Medea pattern of differential mortality of genotypes within maternal families. Although each M factor tested had similar properties of maternal lethality to larvae and zygotic self-rescue, M factors representing distinct loci did not show cross-rescue. Alleles at two of these loci, M1 and M4, were by far the most prevalent, M4 being the predominant type. M2 and M3 were each found only once, in Pakistan and Japan, respectively. Although M1 could be genetically segregated from M4 and maintained as a purified stock, the M1 factor invariably co-occurred with M4 in field populations, whereas M4 usually occurred in the absence of other Medea factors. The dominant maternal lethal action of M1 could be selectively inactivated (reverted) by gene-knockout gamma irradiation with retention of zygotic rescue activity.