TOBACCO CELLS CONTAIN A PROTEIN, IMMUNOLOGICALLY RELATED TO THE NEUTROPHIL SMALL G-PROTEIN RAC2 AND INVOLVED IN ELICITOR-INDUCED OXIDATIVE BURST

Suspension-cultured cells of Nicotiana tabacum generated active oxygen species (AOS) when they mere treated with the proteinaceous elicitor, cryptogein. This response was blocked by diphenylene iodonium, an inh ibitor of the neutrophil NADPH oxidase. When microsomal extracts of to bacco cells were probed with an antibody directed against the human sm all G protein Rac2, two immunoreactive proteins were detected at 18.5 and 20.5 kDa, The same experiment performed with cytosolic extracts of tobacco cells led to the observation of a strong immunoreactive prote in at 21.5 kDa only in the cryptogein-treated cells, The appearance of this cytosolic protein was related to the production of AOS by the el icited cells, These results provide evidence for the possible involvem ent of small G proteins, homologous to the neutrophil Rac2 protein, in the regulation of the elicitor-induced oxidative burst in plant. (C) 1997 Federation of European Biochemical Societies.