Divergent Functional Diversification Patterns in the SEP/AGL6/AP1 MADS-Box Transcription Factor Superclade.

Members of () and ()/ () MADS-box transcription factor subfamilies play key roles in floral organ identity determination and floral meristem determinacy in the rosid species Arabidopsis (). Here, we present a functional characterization of the seven / and four / genes in the distant asterid species petunia ( × ). Based on the analysis of single and higher order mutants, we report that the petunia // orthologs together with encode classical floral organ identity and floral termination functions, with a master role for the petunia ortholog (). By contrast, the subclade members and , for which no clear ortholog is present in Arabidopsis, play a major role in determining floral meristem identity together with , while contributing only moderately to floral organ identity. In turn, the four members of the petunia / subfamily redundantly are required for inflorescence meristem identity and act as B-function repressors in the first floral whorl, together with / genes. Overall, these data together with studies in other species suggest major differences in the functional diversification of the / and / MADS-box subfamilies during angiosperm evolution.plantcell;31/12/3033/FX1F1fx1.