MEK1/2 and p38-like MAP kinase successively mediate H(2)O(2) signaling in Vicia guard cell.

As a second messenger, H(2)O(2) generation and signal transduction is subtly controlled and involves various signal elements, among which are the members of MAP kinase family. The increasing evidences indicate that both MEK1/2 and p38-like MAP protein kinase mediate ABA-induced H(2)O(2) signaling in plant cells. Here we analyze the mechanisms of similarity and difference between MEK1/2 and p38-like MAP protein kinase in mediating ABA-induced H(2)O(2) generation, inhibition of inward K(+) currents, and stomatal closure. These data suggest that activation of MEK1/2 is prior to p38-like protein kinase in Vicia guard cells.