Isobutyl Isothiocyanate is a Potent Heat Tolerance Enhancer for Arabidopsis

Heat tolerance enhancers are chemicals which prevent the physiological damages of plants by heat. Phenethyl isothiocyanate (ITC), which is known as the heat tolerance enhancer, induced the expression of heat shock protein genes in Arabidopsis . Here we measured the heat shock response (HSR)-inducing activities of ITCs to find more active ITCs than phenethyl ITC. We prepared transgenic Arabidopsis possessing the b - glucuronidase reporter gene driven by the promoter of a small heat shock protein ( HSP17.6C-CI ) gene which was induced by heat tolerance enhancers. We tested 16 naturally occurring ITCs for their HSR-inducing activities: 5 aromatic ITCs, 7 aliphatic ITCs, and 4 sulfur-containing aliphatic ITCs. The results showed that the short-chain aliphatic ITCs, especially isobutyl ITC, promoted the HSR more strongly than the aromatic and sulfur-containing aliphatic ITCs. Isobutyl ITC induced the HSR in the whole Arabidopsis seedlings. The isobutyl ITC-treated plants showed higher heat tolerance than the phenethyl ITC-treated plants. These results suggest that isobutyl ITC is a more potent heat tolerance enhancer than phenethyl ITC.