Genetic regulation of shoot development in Arabidopsis: role of the EMF genes.

To investigate the genetic mechanism regulating Arabidopsis shoot maturation and development, we characterized eight emf mutants that bypassed the vegetative phase of the life cycle. Genetic complementation studies identified two EMF loci; both mapped to chromosome five. Double mutant analysis showed that the early- and late-flowering mutants, co, fb, elf1, elf2, and elf3, could not rescue vegetative development in the emf mutants, confirming the need for both EMF gene activities for rosette development. A series of phenotypes involving successive loss of reproductive organs was also observed in emf single mutants, in emf1-1/emf1-2 transheterozygotes, and in emf1 emf2 double mutants, suggesting that the EMF genes not only specify the rosette (vegetative) but also are involved in inflorescence and flower (reproductive) development. Phenotypic analysis of double mutants between emf and tfl1, lfy, and ag indicated interactions between EMF and genes regulating inflorescence meristem development and floral organ identity. A model depicting the role of the EMF genes in regulating shoot maturation and their interaction with genes that affect phase transitions is presented.