TEMPORAL RELATIONSHIP BETWEEN THE TRANSCRIPTION OF 2 ARABIDOPSIS MADSBOX GENES AND THE FLORAL ORGAN IDENTITY GENES

MADS box genes play important roles in specifying floral meristem and floral organ identity. We characterized the temporal and spatial expre ssion patterns of two members of this gene family, AGL4 and AGL5 (for AGAMOUS [AG]-like). AGL4 RNA initially accumulates after the onset of expression of the floral meristem identity genes but before the onset of expression of the floral organ identity genes. AGL4 is, therefore, a putative target of the floral meristem identity genes and/or a poten tial regulator of the floral organ identity genes. AGL5 is initially e xpressed early in carpel development, shortly after the onset of AG ex pression. The loss of AGL5 expression in flowers of ag mutants, the ac tivation of AGL5 by ectopic expression of AG, and the specific binding of AG to an element in the AGL5 promoter identify AGL5 as a putative direct target of AG. Our study provides possible links between the est ablishment of floral meristem and floral organ identity as well as sub sequent steps in flower development.