EMF GENES REGULATE ARABIDOPSIS INFLORESCENCE DEVELOPMENT

Mutations in EMBRYONIC FLOWER (EMF) genes EMF1 and EMF2 abolish rosett e development, and the mutants produce either a much reduced infloresc ence or a transformed flower. These mutant characteristics suggest a r epressive effect of EMF activities on reproductive development. To inv estigate the role of EMF genes in regulating reproductive development, we studied the relationship between EMF genes and the genes regulatin g inflorescence and flower development. We found that APETALA1 and AGA MOUS promoters were activated in germinating emf seedlings, suggesting that these genes may normally be suppressed in wild-type seedlings in which EMF activities are high. The phenotype of double mutants combin ing emf1-2 and apetala1, apetala2, leafy1, apetala1 cauliflower, and t erminal flower1 showed that emf1-2 is epistatic in all cases, suggesti ng that EMF genes act downstream from these genes in mediating the inf lorescence-to-flower transition. Constitutive expression of LEAFY in w eak emf1, but not emf2, mutants increased the severity of the emf phen otype, indicating an inhibition of EMF activity by LEAFY, as was deduc ed from double mutant analysis. These results suggest that a mechanism involving a reciprocal negative regulation between the EMF genes and the floral genes regulates Arabidopsis inflorescence development.