Homoglutathione Synthesis in Transgenic Tobacco Plants Expressing Soybean Homoglutathione Synthetase

Homoglutathione (hGSH) is present in some leguminous plants including soybean and bean. However, hGSH synthesis in non-leguminous plants has not been reported so far. We constructed transgenic tobacco plants expressing soybean hGSH synthetase (hGSHS). Although the transgenic tobacco plants exhibited higher hGSHS activity than glutathione (GSH) synthetase activity, hGSH content was much lower than GSH content. Precursor feeding experiments revealed that hGSH synthesis was limited by the availability of both γ-L-glutamyl-L-cysteine and β-alanine. The result also suggests that the major site of GSH synthesis in tobacco plants is not cytosol.