PFCRC mediates neofunctionalization of Physalis GLOBOSA genes in carpel development.

Floral B-function MADS-box genes, such as GLOBOSA (GLO), have been demonstrated to play roles in corolla and stamen organ identity specification. The functions of these genes outside of these floral whorls are rarely reported. Pollinated with wild-type pollen, the fruit set was extremely low in the mutant of Double-Layered-Lantern 1 (DOLL1), a GLO gene controlling corolla and androecium organ identity in Physalis floridana, indicating that doll1 females are dysfunctional. We found that stigma and style structure, stigma receptivity, pollen tube guidance, and embryo sac development were impaired in doll1; P. floridana CRABS CLAW (PFCRC), predominantly expressed in carpels, was repressed in the doll1 native carpels. Loss-of-function of PFCRC altered carpel meristem determinacy, carpel closure, and ovule number, and the resultant 'pistil' consisted of multiple spirally-arranged dorsiventral carpels occasionally with 1-2 naked ovules on the margin and trichomes at each mutated carpel tip, implying an alteration of carpel organ identity. We further revealed the regulatory and genetic interactions between B-class MADS-box genes and PFCRC in a context-dependent manner, and their developmental roles in floral development. Our work reveals a new role in carpel and ovule development for the B-function genes via regulating PFCRC, thus providing a new understanding of genetic regulatory networks between MADS-domain and CRC transcription factors in regulating carpel organ specification, functionality, and origin.