The mitogen-activated protein kinase (MAP Kinase) cascade is one of the major pathways by which extracellular stimuli are transduced into intracellular responses in plants. MAP Kinases have been shown to play important roles in plant growth and development, and in responding to environmental stresses. In this issue, Wang et al. (442–452) report the isolation and functional analysis of a novel MAP Kinase gene, ZmMPK3
, from maize. The expression profile and kinase activity suggest that Zm
is involved in delivering various stress signals in maize leaves.