Transformed plants with elevated levels of chloroplastic SOD are not more resistant to superoxide toxicity.
The petunia nuclear gene which encodes the chloroplast isozyme of superoxide dismutase, SOD-1, has been fused with an efficient rbcS promoter fragment and 3' flanking region and introduced into tobacco and tomato cells. Transformed plants carrying this chimeric gene have up to 50-fold the levels of SOD-1 which occur in wild-type plants. However, tobacco plants with 30- to 50-fold the normal SOD-1 activity do not exhibit resistance to the light-activated herbicide paraquat. Similarly, tomato plants with 2- to 4-fold increases in SOD-1 do not exhibit tolerance to photoinhibitory conditions known to increase superoxide levels (high light, low temperatures and low CO2 concentrations). Our data indicate that increasing the chloroplastic SOD level in a plant cell is not sufficient to reduce the toxicity of superoxide.
Tepperman
J M
JM
DNA Plant Technology Corporation, Oakland, CA 94608.
Dunsmuir
P
P
D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D003001:Cloning, Molecular; D015870:Gene Expression / Q000187:drug effects / Q000528:radiation effects; D005818:Genetic Engineering; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008027:Light; D010269:Paraquat / Q000633:toxicity; D010944:Plants / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D010947:Plants, Toxic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013482:Superoxide Dismutase / Q000235:genetics / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic
D007527:Isoenzymes; D012333:RNA, Messenger; D013481:Superoxides; D013482:Superoxide Dismutase; D010269:Paraquat