Identification of pathways directly regulated by SHORT VEGETATIVE PHASE during vegetative and reproductive development in Arabidopsis.

Background: MADS-domain transcription factors play important roles during plant development. The Arabidopsis MADS-box gene SHORT VEGETATIVE PHASE (SVP) is a key regulator of two developmental phases. It functions as a repressor of the floral transition during the vegetative phase and later it contributes to the specification of floral meristems.

The Arabidopsis floral meristem identity genes AP1, AGL24 and SVP directly repress class B and C floral homeotic genes.

During the initial stages of flower development, floral meristems increase in size without the formation of floral organs. When a critical meristem size is reached, the floral meristem begins to develop the floral organs. The first stages of flower development are characterized by the expression of genes such as Apetala 1 (AP1), cauliflower (CAL), AGAMOUS-LIKE 24 (AGL24) and short vegetative phase (SVP).

AGAMOUS-LIKE24 and SHORT VEGETATIVE PHASE determine floral meristem identity in Arabidopsis.

The formation of flowers starts when floral meristems develop on the flanks of the inflorescence meristem. In Arabidopsis the identity of floral meristems is promoted and maintained by APETALA1 (AP1) and CAULIFLOWER (CAL). In the ap1 cal double mutant the meristems that develop on the flanks of the inflorescence meristem are unable to establish floral meristem identity and develop as inflorescence meristems on which new inflorescence meristems subsequently proliferate.

AGL24, SHORT VEGETATIVE PHASE, and APETALA1 redundantly control AGAMOUS during early stages of flower development in Arabidopsis.

Loss-of-function alleles of AGAMOUS-LIKE24 (AGL24) and SHORT VEGETATIVE PHASE (SVP) revealed that these two similar MADS box genes have opposite functions in controlling the floral transition in Arabidopsis thaliana, with AGL24 functioning as a promoter and SVP as a repressor. AGL24 promotes inflorescence identity, and its expression is downregulated by APETALA1 (AP1) and LEAFY to establish floral meristem identity. Here, we combine the two mutants to generate the agl24 svp double mutant.