Plant homologues of components of MAPK (mitogen-activated protein kinase) signal pathways in yeast and animal cells.

As they respond to numerous extracellular and intracellular stimuli, plants develop various morphological features and the capacity for a large variety of physiological processes during their growth. If we are to understand the molecular basis of such developments, we must elucidate the way in which signals generated by such stimuli can be transduced into plant cells and transmitted by cellular components to induce the appropriate terminal events. In yeast and animal systems, signal pathways that are known collectively as MAPK (mitogen-activated protein kinase) cascades have been shown to play a central role in the transmission of various signals. The components of these pathways include the MAPK family, the activator kinases of the MAPK family (the MAPKK family) and the activator kinases of the MAPKK family (the MAPKKK family). The members of each respective family are structurally conserved and signals are transmitted by similar phosphotransfer reactions at corresponding steps that are mediated by a specific member of each family in turn. Both cDNAs and genes that encode putative homologues of these components have recently been isolated from plant sources. Some of them have been shown to be related not only structurally but also functionally to members of the MAPK cascades of other organisms. These findings suggest that plants have signal pathways that are analogues to the MAPK cascades in yeast and animal cells but it remains to be proven that plant homologues do in fact constitute kinase cascades.(ABSTRACT TRUNCATED AT 250 WORDS)