Genetic interaction between GROWTH-REGULATING FACTOR and CUP-SHAPED COTYLEDON in organ separation.

The Arabidopsis thaliana GROWTH-REGULATING FACTOR (GRF) gene family comprises 9 members and encodes a class of transcription factors. We previously demonstrated that GRF genes played an essential role in formation of the boundary region between cotyledons, since their loss-of-function mutants developed fused cotyledons. Our present study shows that the grf mutants display fused floral organs as well. Such fusion phenotypes of embryonic and post-embryonic floral organs are highly reminiscent of the cup-shaped cotyledon (cuc) mutants. In order to test a genetic interaction between GRFs and CUCs, we constructed cuc1 grf1/2/3, cuc2 grf1/2/3, and cuc3 grf1/2/3 quadruple mutants, and found that the mutants showed dramatic increases in cotyledon fusion as well as floral organ fusion. The results suggest that the signaling pathway of GRFs may be genetically associated with that of CUCs in the organ separation process.