Article Figures & Data
Figures
- Fig. 1.
Total non-protein thiol contents in control andcys1 transgenic plants. A, The fourth distal leaf of unfumigated 7-week-old plants; B, the sixth distal leaf of 5-month-old tobacco plants either un-fumigated (U), or exposed to 1 μL L−1 SO2(SO2) for 8 h in the light, after which no foliar damage to either control or transgenic plants was observed. Values are means (with se bars) of four independent plants with two duplicates each. SH, Total SH.
- Fig. 2.
Chlorophyll fluorescence and stomatal resistance in control and cys1 transgenic plants during SO2 fumigation. A, Upper, effective quantum yields (Fm' − Fs/Fm') in 3-week-old plants untreated or exposed to 1 μL L−1SO2 (SO2) for 3 or 8 h in the light. A, Lower, stomatal resistance (Stomatal Resist; S cm−1), measured in the same plants after 3 or 8 h of 1 μL L−1SO2. B, Quantum yields (Fm' − Fs/Fm') of 7-week-old plants untreated or exposed to 1 or 2 μL L−1SO2 for 6 h in the light. Values for each experiment are means (with se bars) of five control and seven or eight transgenic plants, each with two independent measurements.
- Fig. 3.
Extent of SO2-induced foliar damage in control and cys1 transgenic plants. The 7-week-old plants were exposed to 2 μL L−1SO2 for 8 h in the light, and then allowed to recover for 24 h before being photographed. Punched leaf discs were used for oxygen evolution measurements (see text).
- Fig. 4.
MV-induced chlorosis and electrolyte leakage in control and cys1 transgenic leaf discs. A, Leaf discs from three different 7-week-old control and transgenic plants were vacuum infiltrated with water (Water) or different MV concentrations (MV; 0.5 μm or 2.0 μm) and then illuminated for 18 h. B, Time course of electrolyte leakage from leaf discs of 7-week-old plants vacuum infiltrated with 20 μm MV or water and then transferred to water in the light for 18 h. Conductivity values (μS cm−1), a measure of cellular damage, were calculated as the difference in leakage between leaf discs exposed to MV and to water in the light. Maximum values for controls and transgenics exposed to water only in the light for 18 h were 26.2 ± 4.3 and 31.2 ± 1.0 μS cm−1, respectively. Values are means (with se bars) of 10 leaf discs from three independent control or transgenic plants.
- Fig. 5.
Northern-blot analysis of cytosolic SOD transcript accumulation in control and cys1 transgenic plants. A, Six leaf discs from the fourth distal leaf of 7-week-old plants exposed to one-fifth Murashige and Skoog media lacking a sulfur source (U), or that supplemented with 10 mmNa2SO4 (sulfate; SO4), 10 mmNa2SO3 (sulfite; SO3), 10 mmNa2S (sulfide; Na2S), or sulfite plus 1 mm O-acetyl-Ser (SO3/OAS) for 18 h in the light. B, Seven-week-old plants untreated (U) or fumigated for 3 h with 2 μL L−1 SO2(SO2) in the light. C, Leaf discs of 7-week-old control plants exposed to one-fifth Murashige and Skoog (U), or that supplemented with the stated concentrations of Cys, GSH, or N-acetyl Cys (N-aC) for 18 h in the light. Leaf discs or leaf samples were immediately used for RNA extraction and northern hybridization using cDNA probes for tobacco cytosolic Cu/ZnSOD or MnSOD, or for wheatcys1. C, Control plants; T, cys1 transgenic plants.
- Fig. 6.
Comparison of relative total cellular SOD activities in control and cys1 transgenic plants. Leaf discs from fourth distal leaves of 7-week-old plants treated with one-fifth MS (U), or that supplemented with 10 mmNa2SO3 and 1 mm O-acetyl-Ser (SO3/OAS) for 18 h in the light. Leaf discs were used to prepare crude samples for SOD determination. Values are means (with se bars) of three plants with two duplicate measurements each.
