XVI International Botanical Congess

Generation of bilateral symmetry in A. majus requires the action of several genes. One of these genes, cycloidea, is expressed in the dorsal region of the floral meristem, and gives a mutant phenotype in which the flower shape is ventralised. We are using RNA in situ hybridsation to study the Cyc expression pattern is CIC- and trans-acting mutants. The CIC-acting mutants are of two types L: those which produce a ventralised phenotype because of reduced Cyc expression, and those with a dorsalised phenotype due to ectopic Cyc expression in the central petal loves. Expression of Cyc is also altered in some trans-acting mutants. For example, in the null floricaula meristem identity mutant, Cyc expression is abolished, whereas in the organ identity mutants, plena and deficiens, cyc is expressed normally at early stages.