INVOLVEMENT OF JASMONIC ACID IN ELICITOR-INDUCED PHYTOALEXIN PRODUCTION IN SUSPENSION-CULTURED RICE CELLS

It has been suggested that jasmonic acid (JA) could be an integral par t of a general signal transduction system regulating inducible defense genes in plants. It was reported that treatment with an elicitor (N-a cetylchitoheptaose) induced production of phytoalexin in suspension-cu ltured rice (Oryza sativa L.) cells. In this study, the role of JA in the induction of phytoalexin production by N-acetylchitoheptaose was i nvestigated. Exogenously applied (+/-)-JA (10(-4) M) clearly induced t he production of momilactone A, a major phytoalexin, in suspension-cul tured rice cells. On the other hand, in rice cells treated with N-acet ylchitoheptaose, endogenous JA was rapidly and transiently accumulated prior to accumulation of momilactone A. Treatment with ibuprofen, an inhibitor of JA biosynthesis, reduced production of momilactone A in t he cells treated with N-acetylchitoheptaose, but the addition of (+/-) -JA increased production of momilactone A to levels higher than those in the elicited rice cells. These results strongly suggest that JA fun ctions as a signal transducer in the induction of biosynthesis of momi lactone A by N-acetylchitoheptaose in suspension-cultured rice cells.