RELEASE AND BIOLOGICAL-ACTIVITY OF DIFFUSIBLE SIGNAL COMPOUNDS FROM ELICITED PLANT-CELLS

Treatment of cell suspension cultures of soybean, alfalfa, or tobacco with macromolecular elicitors resulted in the release of low molecular mass (500-2000 u (Dal)) endogenous elicitors that could pass through a dialysis membrane into the surrounding culture medium. The active co mpounds induced phenylalanine ammonia-lyase (PAL) activity in cells of all three species, isoflavonoid phytoalexin accumulation in soybean a nd alfalfa cells, and an oxidative burst in soybean cells. Release of factors from soybean cells was inhibited by the RNA synthesis inhibito r actinomycin D, but not by diphenylene iodonium, an inhibitor of the oxidative burst. The activity of the factors released from tobacco cel ls in response to the proteinaceous elicitor cryptogein, or from alfal fa cells in response to yeast elicitor, was unaffected by pretreatment with sodium periodate or proteinase K. In contrast, treatment of the factor(s) from soybean cells with proteinase K or trypsin destroyed it s ability to induce the phytoalexin glyceollin. Ion-exchange chromatog raphy revealed that the active material from cell cultures of each spe cies consisted of at least two components. One component released from soybean cells appears to be a small peptide.