Proceedings of the XLVI Italian Society of Agricultural Genetics - SIGA Annual Congress

Giardini Naxos, Italy - 18/21 September, 2002

ISBN 88-900622-3-1

Oral Communication Abstract - S5a

MAPK CASCADES IN HORMONE, STRESS AND DEFENSE SIGNALING

SHEEN J.

Department of Molecular Biology, Massachusetts General Hospital

Department of Genetics, Harvard Medical School

Boston, MA 02114, USA

Mitogen-activated protein kinase (MAPK) cascades are evolutionarily conserved signaling modules with essential regulatory functions in eukaryotes, including yeasts, worms, flies, frogs, mammals, and plants. Numerous studies have shown that plant MAPKs are activated by abiotic stresses, pathogens and pathogen-derived elicitors, and plant hormones. The Arabidopsis genome and EST sequencing projects have revealed large gene families encoding MAPKs and their immediate upstream regulators, MAPKKs and MAPKKKs. However, little is known about the constitution of plant MAPK cascades and the specific roles that particular MAPK cascade genes play in particular plant signal transduction pathways. We have developed a comprehensive approach based on genomic information, transient expression assays, and transgenic and genetic analyses to determine the function of all Arabidopsis MAPK cascade genes involved in essential plant signaling pathways. The transient nature of the protoplast systems allows direct functional analysis of plant genes at an unprecedented high throughput rate. The experimental approaches are especially powerful in unraveling the functions of genes that are difficult to tackle by traditional genetic and biochemical approaches due to redundancy, lethality or low levels of expression. The involvement of MAPK cascades in hormonal, stress and innate immune responses will be presented. Since the functions of MAPK cascades in plant signal transduction pathways are likely conserved, our studies using the Arabidopsis genome resources will have broad implications and applications in other plant species. The elucidation and manipulation of MAPK cascades in plants has revealed fundamentally important intracellular signaling processes and provided new tools for crop improvement in stress tolerance, disease resistance, and yield enhancement.