Gene Control of Specificity and Activity : Loss by Mutation and Restoration by Complementation

Abstract

THE S gene, controlling the incompatibility reaction between pollen and styles in plants, exists in a very large number of ‘alleles’, each producing a characteristic antigen in the pollen and a similar antigen with the same specific activity in the style, through which the pollen tube must grow to achieve fertilization. Mutations and recombination of this gene in Oenothera organensis, selected out of 10⁹ genes, have been of one type only¹. The chief feature about these mutant S alleles is their complete loss of activity in the pollen, so that no active antigen could be detected by the sensitive pollen-style tests. The favoured² interpretation was that one part or area of the gene was determining specificity and another area determining a carrier responsible for the activity in pollen and style. The mutant change would then be some defect in the activity-determining area of the gene. With this interpretation it must be concluded that none of the mutants gave an active and changed specificity but only a loss of activity.