Abstract
Glutamine synthetase (GS) is one of the key enzyme that plays a central role in N-assimilation in plants. We have previously prepared transgenic tobacco with high level of GS2 by Agrobacterium-mediated nuclear transformation and showed a large capacity for photorespiration and high tolerance against high light in tobacco plants. In the present report, we tried to develop overexpressors of GS2 by means of chloroplast transformation.
A rice GS2 cDNA without a transit peptide is expressed from the plastid psbA promoter and 5'-untranslated region, known to be up-regulated in green leaves. The GS2-expressing cassette was introduced into tobacco chloroplast genome by homologous recombination. The expression of GS2 in the transplastomic tobacco was 30-40 times higher than that in wild-type plants. The enzymatic activity of GS in the transplastomic tobacco was 7-9 times higher than that in wild-type plants. The physiological feature of the transplastomic tobacco is under investigation.
