Expression of a gibberellin-induced leucine-rich repeat receptor-like protein kinase in deepwater rice and its interaction with kinase-associated protein phosphatase

We identified in deepwater rice (Oryza sativa L.) a gene encoding a leucine -rich repeat receptor-like transmembrane protein kinase, OsTMK (O. sativa t ransmembrane kinase). The transcript levels of OsTMK increased in the rice internode in response to gibberellin. Expression of OsTMK was especially hi gh in regions undergoing cell division and elongation. The kinase domain of OsTMK was enzymatically active, autophosphorylating on serine and threonin e residues. A cDNA encoding a rice ortholog of a kinase-associated type 2C protein phosphatase (OsKAPP) was cloned. KAPPs are putative downstream comp onents in kinase-mediated signal transduction pathways. The kinase interact ion domain of OsKAPP was phosphorylated in vitro by the kinase domain of Os TMK. RNA gel-blot analysis indicated that the expression of OsTMK and OsKAP P was similar in different tissues of the rice plant. In protein-binding as says, OsKAPP interacted with a receptor-like protein kinase, RLK5 of Arabid opsis, but not with the protein kinase domains of the rice and maize recept or-like protein kinases Xa21 and ZmPK1, respectively.