The Arabidopsis shaggy-related kinases (ASKs) are plant kinases that are structurally similar to a Drosophila kinase, shaggy, which has key roles in development. ASKs are also similar to glycogen synthase kinase 3 isoforms, which are found in plants as well as animals. Bikinin is an inhibitor of several ASK isoforms when given at a concentration of 10 μM. After bikinin treatment, residual kinase activity was less than 10% for ASKα, γ, ε, ζ, η, ι, and 20% for ASKθ, while isoforms β and δ were not affected. Bikinin has little or no direct effect on a wide range of other kinases. By inhibiting ASKs, bikinin activates signaling induced by the brassinosteroid, brassinolide. Bikinin blocks the phosphorylation of SnRK2.3 by ASKη (also known as BIN2), upregulating signaling through abscisic acid . Bikinin has been used to study the role of ASK-modulated brassinosteroid signaling in wheat and in viral infection of plants.
