A novel rice MAPK gene, OsBIMK2, is involved in disease-resistance responses

The mitogen-activated protein kinase (MAPK) cascades play important roles in transmission of extracellular signals to the downstream effector proteins through a mechanism of protein phosphorylation. In this study, we isolated and identified a novel rice MAPK gene, OsBIMK2 (Oryzae sativa L. BTH-Induced MAP Kinase 2). The OsBIMK2 encodes a 506 amino acid protein with molecular weight of 63 kD. The recombinant OsBIMK2 expressed in Escherichia coli showed an autophosphorylation activity in vitro. OsBIMK2 is a single-copy gene in the rice genome. Expression of OsBIMK2 was activated upon treatment with benzothiadiazole (BTH), which is capable of inducing disease resistance in rice. Expression of OsBIMK2 was also up-regulated during early stage after inoculation with Magnaporthe grisea in BTH-treated rice seedlings and during an incompatible interaction between M. grisea and a blast-resistant rice genotype. Over-expression of the rice OsBIMK2 gene in transgenic tobacco resulted in an enhanced disease resistance against tomato mosaic virus and a fungal pathogen, Alternaria alternata. These results suggest that OsBIMK2 plays a role in disease resistance responses.