Morphological and molecular analyses of the tomato floral mutant leafy inflorescence, a new allele of falsiflora

The purpose of this study was to advance understanding of the molecular mechanisms of tomato floral development that differ from those of Arabidopsis, through morphological and molecular biological analyses of the tomato floral mutant leafy inflorescence (lfi). In lfi inflorescences, shoot apex-like meristems have indeterminate growth and develop into large leafy inflorescence that fail to flower. A 12 bp deletion was found in the 3′ region of the open reading frame of FALSIFLORA (FA), the tomato ortholog of the Arabidopsis floral meristem identity gene LEAFY, in the lfi mutant. An allelism test indicated that lfi is allelic to falsiflora. Because the FA locus controls floral meristem identity, expression analyses of several floral organ identity genes were carried out to deduce the relationship between these genes and FA. Expression of the tomato floral organ identity genes TDR6 and TAG1 was inhibited in lfi inflorescences, suggesting that FA induces tomato floral organ identity genes, as LEAFY does in Arabidopsis. In addition, FA promoted the induction of the SEP3 ortholog, TDR5, although TDR4 was not regulated by FA. The investigation of ectopic carpel formation, a unique feature of lfi, suggested that TAG1 (a group C gene) and TDR5 have important roles in carpel formation, as in Arabidopsis. However, the expression of TDR6, which is thought to be a group B gene, is also associated with ectopic carpel formation, unlike in Arabidopsis.