AN S-LOCUS-RELATED GENE IN ARABIDOPSIS ENCODES A FUNCTIONAL KINASE AND PRODUCES 2 CLASSES OF TRANSCRIPTS

ARK1 is a vegetatively expressed receptor protein kinase gene isolated from Arabidopsis thaliana based on its sequence similarity to Brassic a genes involved in pollen-stigma signaling and the self-incompatibili ty response. This paper shows that the kinase domain of ARK1 autophosp horylates on serine and threonine residues when expressed as a recombi nant fusion protein. ARK1 produces a 2.9 kb transcript encoding a tran smembrane receptor protein kinase and a 1.4 kb transcript encoding the receptor domain alone. Constitutive high-level expression of ARK1 tra nscripts in transgenic Arabidopsis resulted in severe stunting and als o disrupted normal cellular expansion and differentiation.