Putative incompatibility proteins in distylous Turnera species: Immunoblot and immunocytochemistry analyses

Self-incompatibility was investigated in distylous Turnera species (Turneraceae) by using polyclonal antibodies raised against recombinant proteins specific to styles and pollen of the short-styled morph. Style and pollen immune serums were used in IEF-, SDS-immunoblotting and immunocytochemisty experiments to study and localize proteins specific to the short-styled morph. In IEF-immunoblotting experiments, style immune serum reacted with proteins specific to styles, and pollen immune serum with proteins specific to the pollen. In SDS-immunoblotting, style immune serum detected a single 40 Kd band in styles of the short-styled morph. This 40 Kd band did not appear in styles of the long-styled morph or any other floral tissues examined. Pollen immune serum detected a single 55 Kd band in pollen of both morphs, but not in any other floral tissues examined. In immunocytochemistry experiments, style immune serum localized the 40 Kd protein to the transmitting tissue (where pollen tube growth takes place). This supports the hypothesis that the 40 Kd style protein is involved in incompatibility. Because the pollen protein appears in both morphs, it likely plays no direct role in incompatibility.

Using SDS-PAGE and comparing protein profiles of styles from short- and long-styled morphs, a 68 Kd protein specific to the styles of the short-styled morph was identified. Exploring 66 individuals from different species of Turnera showed the consistent appearance of S68 in styles of the short morph but not in the long. Neither style nor pollen immune serum reacted with S68 indicating that S68 is a novel protein possibly involved in self-incompatibility.