Inhibition of chloroplast development by tentoxin

Light-dependent chloroplast development in detached pea shoots was measured in terms of chlorophyll synthesis and the synthesis of Fraction 1 protein. Both synthetic processes were inhibited more than 90% by the fungal metabolite, tentoxin (1 or 10 μg/ml). These results place Pisum sativum in the class of tentoxin-sensitive higher plants. Tentoxin, actinomycin D, lincomycin, D-threo-chloramphenicol and carbonyl cyanide m-chlorophenyl-hydrazone (CCCP) were compared in their ability to inhibit RNA and protein synthesis by isolated pea chloroplasts. Energy for the synthetic reactions was supplied either by light or by added ATP. Only CCCP gave the same pattern of inhibition as tentoxin, i.e. inhibition of both RNA and protein synthesis in the light-driven system but no inhibition in the ATP-driven system. It is concluded that chloroplast developmental processes are inhibited by tentoxin through the inhibition of photophosphorylation.