Fig. 5.

Effects of hormones on the mRNA levels of thiol synthetase genes (A), homoglutathione synthetase (hGSHS) activity (B), and thiol contents (C) in roots of Lotus japonicus. No glutathione synthetase (GSHS) activity could be detected in any of the root extracts. Non-nodulated and nodulated plants were supplied for 48 h with 50 μM of hormones in the rooting medium. Steady-state mRNA levels of γ-glutamylcysteine synthetase (γECS), glutathione synthetase (GSHS), and homoglutathione synthetase (hGSHS) were normalized to ubiquitin mRNA levels and expressed relative to those of control plants (C). These were treated for 48 h with identical concentrations of NaOH (IAA and CK), ethanol (ABA, SA, and PA), or dimethylsulphoxide (JA) to those used to prepare the stock solutions of hormones. The mRNA levels of control plants were given a value of 1. Data of mRNA levels are means ± SE of four or five replicates, corresponding to RNA extractions of different roots from two series of plants grown independently (two or three replicates per series). Asterisks denote upregulation (>2-fold) or downregulation (<0.5-fold) of the genes. Values of thiol contents and enzyme activity of control plants were obtained from roots harvested immediately before the hormone treatments. Data of thiol contents and enzyme activity are means ± SE of four or six replicates, corresponding to extractions of different roots from two series of plants grown independently (two or three replicates per series). Asterisks denote that the means of the hormone treatments are significantly different from the control at P < 0.05 based on Student’s t-test.