Involvement of β-cyanoalanine synthase (β-CAS) and sulfurtransferase (ST) in cyanide (CN-) assimilation in rice seedlings

In spite of available information demonstrating the assimilation of cyanide (CN-) by beta-cyanoalanine synthase (beta-CAS) in plants, involvement of sulfurtransferase (ST) in CN- assimilation in rice plants is still undefined. In this study, a microcosmic hydroponic system was used to investigate the involvement of beta-cyanoalanine synthase (beta-CAS) and sulfurtransferase (ST) in the CN- assimilation in rice seedlings under the exposure of potassium cyanide (KCN) in presence or absence of 1-amino-cyclopropane-1-carboxylic acid (ACC). Our results indicated that the measurable thiocyanate (SCN-) was detected in both rice roots and shoots under KCN exposure, and the abundances of ST-related transcripts were up-regulated significantly (p < 0.05), suggesting that the ST pathway is involved in CN- assimilation in the rice plants. The application of exogenous ACC significantly (p < 0.05) decreased the accumulation of CN- and SCN- in rice tissues after KCN exposures, and also up-regulated the expression of beta-CAS and ST genes and their enzymatic activities, suggesting a positive interaction between aminocyclopropane-1-carboxylate oxidase (ACO), beta-CAS and ST in rice plants during the CN- assimilation. This is the first attempt to experimentally clarify the involvement of ST in CN- assimilation in rice seedlings.