SEX DETERMINATION GENE TASSELSEED2 OF MAIZE ENCODES A SHORT-CHAIN ALCOHOL-DEHYDROGENASE REQUIRED FOR STAGE-SPECIFIC FLORAL ORGAN ABORTION

Maize produces separate unisexual flowers through programed abortion o f preformed organ primordia. In the male inflorescence (tassel), stame n primordia develop to sexual maturity, while gynoecia (pistil primord ia) are aborted. In tasselseed2 (ts2) mutant plants, floral structures in the tassel adopt a female developmental program. Here we report th e transposon tagging and cloning of the TS2 gene, which plays a late b ut pivotal role In determining the sexual fate of floral meristems. Sh ortly before abortion of the gynoecium, Ts2 mRNA is expressed subepide rmally in that primordium. Phenotypic instability of the Activator (Ac )-induced allele ts2-m1 indicates that late restoration of TS2 action in somatic tissues, which is correlated with Ac excision, reactivates the male developmental program. The predicted amino acid sequence of t he Ts2 protein shows significant similarity to short-chain alcohol deh ydrogenases, particularly hydroxysteroid dehydrogenases.