DEVELOPMENTAL DIFFERENCES IN ACTION OFRANDBALLELES IN MAIZE

Abstract

Alleles of the B and R loci collected from different geographic races of maize differ with respect to concentration, pattern, and tissue specificity of anthocyanin formation. No differences were found between the pigments formed by B action and those formed by R action. The activities of four B alleles and five R alleles when compared in a common genetic background and described in terms of the whole life cycle show differences in the following respects: In a given tissue, for example the aleurone, there are differences in a) rate of activity, b) time of onset of activtiy, c) time that activity ceases. Apparent tissue specificity is shown when the development of a tissue coincides with the period during which the gene is active. True tissue specificity is shown by alleles that have different activities in tissues that develop at the same time. This latter type of specificity was shown only by alleles known to consist of more than one synaptically homologous region, or by those derived in some way from such complex alleles. It is suggested that for most genetic systems there probably exists potential for change in level of action, change in time of onset and termination of activity, and change toward tissue specificity. The type and extent of the change tolerated will depend on the system involved.