Figure 6From: Functional analysis of B and C class floral organ genes in spinach demonstrates their role in sexual dimorphismModel for the evolution of dioecy in spinach. In the ancestral hermaphroditic species, upstream elements, including but not limited to GA and LFY, activate both B (PI and AP3) and C (AG) class genes. Both classes of genes retain organ identity functions as described in the ABC model. Mutations in the B class genes, notated by *, result in premature termination of the flower in the third whorl, and thus the loss of the carpel. The resultant flower is male. Inactivation or suppression of expression of the B class genes, modulated by the GA response pathway, results in the expression of AG only. The absence of B class gene products causes a reduction in the number of organs in the first whorl and the formation of a single, terminal carpel. The resultant flower is female.Back to article page