Fig. 10. A model of DL and SPW1 functions in floral organ specification. The model is also based on data that indicate the presence of class A and C gene(s) in rice (for a review, see Goto et al., 2001). (A) In the wild-type flower, DL acts in whorl 4 and specifies carpel identity (Ca) together with class C gene(s). SPW1 acts in whorl 2 and 3 as one of the B function genes and specifies stamen identity (St) in whorl 3 together with class C gene(s) and lodicule identity (Lo) in whorl 2 together with class A gene(s). (B) In dl mutants, SPW1 function expands to whorl 4, which results in the homeotic transformation of the carpel into stamens. (C) In spw1 mutants, stamens are transformed into carpels by the ectopic activity of DL in whorl 3. Whorl 2 organs are specified as palea-like (Pl) through the class A function alone. (D) In the spw1-1 dl-sup1 double mutant, organs with unknown identity (Id) are formed in whorls 3 and 4 without class B or DL functions. Organs in whorl 2 are palea-like, the same as those formed in spw1 mutants, specified by the class A function alone (see text). Pa, palea.