Tentoxin‐induced loss of plastidic polyphenol oxidase

Tentoxin‐treated mung bean plants are shown to lack chloroplast polyphenol oxidase (PPO) by enzymatic, electrophoretic and cytochemical analysis. Incorporation of PPO (a protein coded by nuclear DNA) into the plastid may occur via concentration of the protein into inner envelope‐derived vesicles. PPO integration into the plastid is apparently blocked by a tentoxin treatment although fraction I protein (and hence the proteins for chloroplast ribosome production) is not affected by this fungal toxin. Both apical and etiolated plastids from teotoxin‐treated plants lack PPO. Thus, it is unlikely that the primary effect of tentoxin is due to the binding of the chloroplast coupling factor, as previously supposed.