Duplicate MADS-box genes with split roles and a genetic regulatory network of floral development in long-homostyle common buckwheat.

Abstract

The classic ABC model postulates how three classes of floral homeotic genes (A, B and C) work in a combinational way to confer organ identity to each whorl that make up a perfect flower in core eudicot plants. Fagopyrum esculentum (Polygonaceae) produces dimorphic flowers with single whorl showy tepals, representing a considerable difference with most core eudicots flowers. Here, we explain in detail the function of a duplicated pair of floral homeotic genes involved in the formation of tepals and stamens in the LH F. esculentum. FaesAP1_1 and FaesAP1_2 work together to specify tepal identity. FaesAP3_1/2 or FaesPI_1/2 have redundant function in specifying filament identity, while FaesAP3_2 and FaesPI_2 also retain a conserved role in specifying anther development and gain novel function in style length determination. However, FaesPI_1 gain novel function in floral color formation. In addition, FaesAG can directly regulate stamen and pistil development or binds to the CArG-box of pFaesPI_1 to indirectly regulate stamen and pistil development by a gene regulatory pathway involving FaesAP1_1/2, FaesAP3_1/2 and FaesPI_1/2. Moreover, FaesAP1_1/2 can directly or indirectly regulate B-class gene (FaesAP3_1/2 and FaesPI_1/2) expression to be involved in floral development. Our work has led to detailed insights into the MADS-box gene regulatory networks that control floral developmental process in LH F. esculentum.