MOLECULAR CONTROL OF OVULE DEVELOPMENT

Enormous progress has been made over the past five years in understand ing the floral homeotic genes, which specify the fate of the floral or gan meristems. More recently, regulatory genes have been cloned from P etunia hybrida and Arabidopsis thaliana that play essential roles in t he development of the ovule - the floral organ that contains the femal e gametophyte. Extensive mutagenesis programmes using Arabidopsis have yielded a number of ovule mutants that reflect the various steps in o vule ontogeny. These mutants, and the identification of the first key regulatory genes involved in ovule development, are powerful research tools for studies on plant reproduction. Moreover, ovule development i s intriguing for evolutionary studies, because the ovule is a relative ly simple organ found in both modern angiosperms and gymnosperms, and their common ancestor.