The present invention relates to the mitogen-activated protein kinase
called MAPK5. The rice MAPK5 gene, its protein and kinase activity were
induced by abscisic acid, pathogen infection, wounding, drought, salt and
cold temperature. However, suppression of MAPK5 expression and kinase
activity in dsRNAi transgenic plants resulted in constitutive expression
of pathogenesis-related genes such as PR-1 and PR-10 but enhanced
resistance to fungal and bacterial pathogens. In contrast, overexpressed
transgenic lines exhibited elevated MAPK5 kinase activity and increased
tolerance to drought, salt and cold stresses. This invention provides
methods for increasing tolerance to abiotic and biotic stress in plant
using MAPK5.