Figure 1.

Interaction of ARC1 with kinase domains from two different S-locus receptor kinases. lexA fusions were tested for their ability to interact with either VP16:ARC1 (A) or VP16 alone (B). Positive interactions resulting in the activation of the HIS3 and lacZ genes were detected by growth in the absence of histidine and β-galactosidase (β-gal) activity. β-Galactosidase activity was measured by using an o-nitrophenyl β-d-galactoside assay and is reported in units of OD₄₂₀/h. (A) Only lexAkinase⁹¹⁰ and lexAkinase^A14 interact with the VP16:ARC1 fusion, resulting in growth in the absence of histidine and detectable levels of β-galactosidase activity. (B) lexAkinase⁹¹⁰ in the presence of VP16 alone shows slight growth in the absence of histidine but no measurable levels of β-galactosidase activity. lexAkinase^A14 in the presence of VP16 alone has higher background activity, resulting in growth in the absence of histidine and measurable levels of β-galactosidase activity. However, the β-galactosidase levels are only 1/17th of that seen for the interaction with VP16:ARC1 in A.