Exogenously applied isothiocyanates enhance glutathione S-transferase expression in Arabidopsis but act as herbicides at higher concentrations

Abstract

Isothiocyanates (ITCs) are sulfur-containing compounds that are generated by the glucosinolate-myrosinase system in plants. Although previous greenhouse studies have demonstrated the phytotoxicity of ITCs, their action modes are still unknown. In this study, we report the physiological responses of Arabidopsis thaliana treated with three exogenous ITCs: methyl ITC, allyl ITC, and phenethyl ITC. Administration of a high dose of each ITC inhibited plant growth and induced severe bleaching in the rosette leaves. The bleaching was concomitant with the elevation of electrolyte leakage and the generation of hydrogen peroxide. Although the three ITCs showed bleaching symptoms, phenethyl ITC was the most potent. A low dose of phenethyl ITC, at which the ITC did not promote leaf bleaching, enhanced the accumulation of transcripts of glutathione S-transferases (GSTs) in Arabidopsis. When 16 GST genes were tested, the levels of transcripts corresponding to 5 of the GST genes were enhanced in response to the phenethyl ITC treatment. In particular, the expression of a Tau class gene (AtGSTU19, At1g78380) responded to the phenethyl ITC treatment. Enhancement of the AtGSTU19 gene expression also occurred in the treatment of both allyl ITC and methyl ITC. These results suggest that the administration of ITCs to Arabidopsis at high doses has an herbicidal effect by inducing oxidative burst-like responses, but that administration at lower doses enhances the expression of specific GST genes in Arabidopsis.

The Physiological Importance of Glucosinolates on Plant Response to Abiotic Stress in Brassica

“…Recently, it has been demonstrated that the exogenous addition of two isothiocyanates, phenethyl- and allyl-isothiocyanates, enhanced heat tolerance in Arabidopsis plants by increasing the expression level of heat shock proteins and H 2 O 2 accumulation [85,86]. It was determined that the mode of action of phenethyl-isothiocyanate (PEITC) was similar to salicylic acid (SA), a heat tolerance inducer that inhibits the catalase activity in plants and produces the H 2 O 2 accumulation [87], but the molecular mechanisms behind the recognition of both compounds may be different and worth study.…”

Administration of isothiocyanates enhances heat tolerance in Arabidopsis thaliana

“…Recently, we reported that ITCs showed herbicidal effects when applied to Arabidopsis at high doses (Hara et al 2010). Before demonstrating the herbicidal effects of ITCs at the field scale, we first attempted to confirm the ITCs' effects on Arabidopsis in the greenhouse.…”

Allyl isothiocyanate (AITC) induces stomatal closure in Arabidopsis

“…In the present study, we found that AITC induced stomatal closure in Arabidopsis accompanied by ROS and NO production as second messengers. At higher than 1 m m , AITC shows cytotoxicity on Arabidopsis (Hara et al . 2010), whereas even 10 µ M AITC significantly induced stomatal closure (Fig.…”

“…So far, Zhao et al . (2008) reported that glucosinolate‐myrosinase system enhances ABA‐inhibition of guard cell inward K + channels and of stomatal opening and Hara et al . (2010) reported that application of exogenous ITCs including AITC is harmful at the higher dosage while at lower concentration enhances glutathione S ‐transferase (GST) activity in Arabidopsis .…”