Rubisco large subunit degradation in a source leaf with or without protease inhibitors (A) and the inhibition of the protease activities by protease inhibitors (B). The Rubisco large subunit (LSU) in the soluble protein extract (PE) of the source leaf (7 days after bolting) is visualized on stain free SDS-PAGE and quantified for the four biological repetitions by Image Lab software (Bio-Rad) at (t0) and after 1 h of incubation at 37°C (t1h) without inhibitors (PE, control conditions) or with specific protease inhibitors: iodoacetamide (PE + CPI; cystein protease inhibitor), aprotinin (PE + SPI; serine protease inhibitor), methanol (PE + Me), methanol and 1–10 phenanthroline (PE + Me + MI; metalloprotease inhibitor), methanol and pepstatin A (PE + Me + API; aspartic protease inhibitor), DMSO (PE + DMSO) or DMSO and MG132 (PE + DMSO + PI; proteasome inhibitor). The most representative biological repetition is shown in panel A and the percentage of degradation (mean value ± SE, n = 4 plants) are indicated below. Panel B presents the inhibition of the protease activities by the proteases inhibitors (expressed as % of LSU degradation observed in control conditions (PE)). In panel B, data are indicated as the mean value ± SE. An asterisks means that the LSU degradation is significantly different between N treatment and # means a significant differences between genotypes (n = 4 plants; * or #= p < 0.05).