Sequence evolution and sex-specific expression patterns of the C class floral identity gene, SpAGAMOUS, in dioecious Spinacia oleracea L.

Development in dioecious cultivated spinach, Spinacia oleracea, is distinguished by the absence of alternative reproductive organ primordia in male and female flowers. Given the highly derived floral developmental program in spinach, we wished to characterize a spinach C class floral identity gene and to determine the patterns of sequence evolution as well as compare the spatial and temporal expression patterns with those of AGAMOUS. The isolated cDNA sequence clusters phylogenetically within the AGAMOUS/FARINELLI C class clade.

Characterization of SpAPETALA3 and SpPISTILLATA, B class floral identity genes in Spinacia oleracea, and their relationship to sexual dimorphism.

Floral organ identity B class genes are generally recognized as being required for development of petals and stamens in angiosperm flowers. Spinach flowers are distinguished in their complete absence of petals in both sexes, and the absence of a developed stamen whorl in female flowers. As such, we hypothesized that differential expression of B class floral identity genes is integral to the sexual dimorphism in spinach flowers.