GENETIC-CONTROL OF BRANCHING PATTERN AND FLORAL IDENTITY DURING PETUNIA INFLORESCENCE DEVELOPMENT

A main determinant of inflorescence architecture is the site where flo ral meristems are initiated, We show that in wild-type Petunia bifurca tion of the inflorescence meristem yields two meristems of approximate ly equal size. One terminates into a floral meristem and the other mai ntains its inflorescence identity, By random transposon mutagenesis we have generated two mutants in which the architecture of the infloresc ence is altered. In the extra petals(-) (exp) mutant the inflorescence terminates with the formation of a single terminal flower, Phenotypic analysis showed that exp is required for the bifurcation of infloresc ence meristems, In contrast, the aberrant leaf non flower(-) (alf) mut ant is affected in the specification of floral meristem identity while the branching pattern of the inflorescence remains unaltered, A weak alf allele was identified that, after bifurcation of the inflorescence meristem, yields a 'floral' meristem with partial inflorescence chara cteristics. By analysing independent transposon dTph1 insertion allele s we show that the alf locus encodes the Petunia FLORICAULA/LEAFY homo log, In situ hybridisation shows that alf is expressed in the floral m eristem and also in the vegetative meristem, Differences and similarit ies between these Petunia mutants and mutations affecting inflorescenc e architecture in other species will be discussed.