Inhibition of anthocyanin synthesis in the first internode of Sorghum bicolor by cobaltous ions. The site of action of cobalt

Abstract

1993. Inhibition of anthocyanin synthesis in the first internode of Sorghum bicolor by eobaltous ions The site of action of cobalt. -Physiol. Plant. 87: 441-446.Cobaltous ions (Co^+) inhibited light-mediated anthocyanin synthesis and phenylalanine ammonia-lyase (PAL; EC 4,3,1,5) activity in excised first internodes of Sorghum bicolor (L,) Moench, Ethephon (an exogenous source of ethylene) restored anthocyanin synthesis and PAL activity, Sulfhydryl-containing compounds like cysteine and glutathione completely restored anthocyanin synthesis and PAL activity, N-ethylmaleimide (NEM), a sulfhydryl reagent, inhibited anthocyanin synthesis and PAL activity; cysteine or glutathione reversed the effect ot NEM, EDTA and other organic acids like citric, malic, oxalic and tartaric acid were also effective in bringing about recovery. It is suggested that the site of action of Co"^ might be at sulfhydryl groups or two adjacent carboxylic groups of a macromoiecule that is involved either in anthocyanin or ethylene biosynthesis.