Studies Of Glutathione Reductase In Plants

Glutathione reductase (GR, EC1.6.4.2) is one of the important antioxidative enzymes for ROS-scavenging. Many physiological data and transgenic studies about GR have shown the importance of GR in the plants. However little is known about how GR affects the other enzymes and antioxidants in the absence and presence of stresses. Here we produced transgenic tobacco plants with decreased cellular GR by RNA interference (RNAi) and measured the changes of the enzymes and antioxidants in ascorbate-glutathione pathway. The main results are following:1. We generated tobacco plants with 30-70% GR activities by RNAi technology using a gene (X76293, gi: 431954) encoding tobacco chloroplastic GR (Creiseen et al., 1995) for the RNAi construct. The Western blot on 2-D page showed that 10 GR isoenzymes were detected in the whole protein from the wild type plants and 3 of them were in chloroplasts which accounted for the most of the total GR protein. The RNAi construct caused suppression of four GR isoforms which located inside and outside of the chloroplasts, this may result from the homologous gene sequence of the four GR isoforms.2. The measurements of photosynthesis and the detection of ROS and MDA contents showed that low GR activities did not result in oxidative stress in igr- transgenic tobacco plants under normal condition. The changes of ascorbate-glutathione cycles were measured in igr-transgenic tobacco plants under normal condition. The results manifested that the 70%-decreased GR activity (in i21, i28 and i42) resulted in the decrease of GSH/GSSG ratio, slight increased total...