Complementation experiments of mutagenized ROXY1 proteins. Wild-type and mutant ROXY genes driven by the ROXY1 promoter were transformed into the roxy1 mutant. Petal phenotypes of transgenic T1 plants were scored, and representative phenotypes are shown. The roxy1 mutant flowers (B) develop only 2.5 petals per flower instead of 4.0 petals as observed in wild-type (WT) flowers (A). The wild-type ROXY1 gene is able to complement the roxy1 mutant (C). In contrast, replacement of the first Leu (L1) with an Ala in the L**LL motif of ROXY1 (ROXY1L1A) or removal of the ALWL motif from the ROXY1 C terminus (ROXY1Δ4) failed to rescue abnormal petal phenotypes of the roxy1 mutant (D). All other mutagenized ROXY1 proteins (ROXY1L2A, ROXY1L3A, ROXY1L2,3A, and ROXY1L1,2,3A) also lost their capacities to complement the roxy1 mutant. At least 50 T1 transformants were analyzed for each construct.