DIFFERENTIAL EXPRESSION OF A NOVEL GENE IN RESPONSE TO CORONATINE, METHYL JASMONATE, AND WOUNDING IN THE COI1 MUTANT OF ARABIDOPSIS

Coronatine is a phytotoxin produced by some plant-pathogenic bacteria. It has been shown that coronatine mimics the action of methyl jasmona te (MeJA) in plants. MeJA is a plant-signaling molecule involved in st ress responses such as wounding and pathogen attack. In Arabidopsis th aliana, MeJA is essential for pollen grain development. The coil (for coronatine-insensitive) mutant of Arabidopsis, which is insensitive to coronatine and MeJA, produces sterile male flowers and shows an alter ed response to wounding. When the differential display technique was u sed, a message that was rapidly induced by coronatine in wild-type pla nts but not in coil was identified and the corresponding cDNA was clon ed. The coronatine-induced gene ATHCOR1 (for A. thaliana coronatine-in duced) is expressed in seedlings, mature leaves, flowers, and siliques but was not detected in roots. The expression of this gene was dramat ically reduced in coil plants, indicating that COI1 affects its expres sion. ATHCOR1 was rapidly induced by MeJA and wounding in wild-type pl ants. The sequence of ATHCOR1 shows no strong homology to known protei ns. However, the predicted polypeptide contains a conserved amino acid sequence present in several bacterial, animal, and plant hydrolases a nd includes a potential ATP/GTP-binding-site motif (P-loop).