Figure 3.

Characterization of the SyGI Gene.

(A) Phylogenetic tree and signs of selective pressure on SyGI-like type-C response regulators (RR) in representative eudicot species. The CRE1-AHK4 histidine kinase, defined as a type-A response regulator, was used as the outgroup. The SyGI-Achn384741 duplication event is estimated to have arisen ∼20 MYA, which postdates the divergence of Actinidiaceae (Ellison et al., 2012).

(B) Expression pattern of SyGI and Achn384741 in flower organs of a male individual from the KE population. SyGI exhibits specific expression in rudimentary carpels. We used rudimentary carpels and normal stamens at stages 1 and 2-3, respectively, which correspond to the earliest stage at which male and female developing structures can be visibly differentiated (Supplemental Figure 1).

(C) Complete male-specific conservation of SyGI in the genomes of a variety of Actinidia species. A. deliciosa is hexaploid, and tetraploid A. arguta and A. macrosperma are shown.

(D) Expression of SyGI and Achn384741 in developing flowers from a variety of Actinidia species. In males, PCR primers detecting both SyGI and Achn384741 only amplified SyGI (see Methods). M, male; F, female.

(E) In higher-ploidy variants of A. arguta, sexuality also cosegregated with the existence of SyGI.