ELICITOR-INDUCED CHANGES IN CA2+ INFLUX, K+ EFFLUX, AND 4-HYDROXYBENZOIC ACID SYNTHESIS IN PROTOPLASTS OF DAUCUS-CAROTA L

Suspension-cultured carrot cells (Daucus carota) and their protoplasts respond to a fungal elicitor prepared from the culture medium of Pythium aphanidermatum by accumulating 4-hydroxybenzoic acid (4-HBA). Protoplasts release the compound into the culture medium. Using (CaCl2)-Ca-45 as a tracer, we were able to demonstrate that the secretion of 4-HBA is preceded by a rapid increase in the Ca2+ influx and a concomitant K+ efflux. If the increased Ca2+ influx was prevented by ethyleneglycol-bis(beta-aminoethyl ether)-N,N'-tetraacetic acid, 4-HBA synthesis was inhibited by 70%. These results are discussed with regard to signal transduction from the plasma membrane to the nucleus of carrot protoplasts.