DEVELOPMENTAL SIGNIFICANCE OF EPIGENETIC IMPOSITIONS ON THE PLANT GENOME - A PARAGENETIC FUNCTION FOR CHROMOSOMES

Developmental and physiological factors can impose heritable metastabl e changes on the plant genome, a fact that was established by maize ge neticists during the 1950s and 1960s, largely through the efforts of R . Alexander Brink and Barbara McClintock. This paper describes a trans genic reporter system that monitors genomic impositions as changes in morpho genetically-determined flower color patterns. The observations reported here on the metastable properties of plant transgenes illustr ate the proposals of Brink and McClintock that chromosomal impositions occur during normal development as ordered sequences of events which contribute to the elaboration of complex developmental patterns. The r elationship between this process and some recent findings about the co ntrol of gene expression in transgenic plants is also discussed. (C) 1 994 Wiley-Liss, Inc.