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Title: ENHANCED TRANSLATION OF A CHOLORPLAST EXPRESSED RBCS GENE RESTORES SSU LEVELS AND PHOTOSYNTHESIS IN NUCLEAR ANTISENSE RBCS PLANTS

Author
item DHINGRA, AMIT - UNIV OF CENTRAL FLORIDA
item PORTIS JR, ARCHIE
item DANIELL, HENRY - UNIV OF CENTRAL FLORIDA

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 3/15/2004
Publication Date: 7/26/2004
Citation: Dhingra, A., Portis Jr, A.R., Daniell, H. 2004. Enhanced translation of a cholorplast expressed Rbcs gene restores SSU levels and photosynthesis in nuclear antisense Rbcs plants [abstract]. American Society of Plant Biologists Annual Meeting. Available: http://abstracts.aspb.org/pb2004/public/P40/7109.html.

Interpretive Summary:

Technical Abstract: Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) is a key enzyme that converts atmospheric carbon to food and supports life on this planet. Its low catalytic activity and specificity for oxygen leads to photorespiration, severely limiting photosynthesis and crop productivity. Consequently, Rubisco is a primary target for genetic engineering. Separate localization of the genes in the nuclear and chloroplast genomes and a complex assembly process resulting in a very low catalytic activity of hybrid Rubisco enzymes, have rendered several earlier attempts of Rubisco engineering unsuccessful. Here we demonstrate, for the first time, that the RbcS gene, when integrated at a transcriptionally active spacer region of the chloroplast genome, in a nuclear RbcS antisense line and expressed under the regulation of heterologous (gene 10) or native (psbA) UTRs, results in the assembly of a functional holoenzyme and normal plant growth under ambient CO2 conditions, fully short-circuiting nuclear control of gene regulation. There was about 150-fold more RbcS transcript in chloroplast transgenic lines when compared to the nuclear RbcS antisense line, while the wild type has 7-fold more transcript. The small subunit protein levels in the gene10/RbcS and psbA/RbcS plants were 60% and 106% respectively of the wild type. Photosynthesis of gene10/RbcS plants was about double that of the antisense plants while that of psbA/RbcS plants was almost completely restored to the wild type rates. These results have opened an avenue for using chloroplast engineering for the evaluation of foreign Rubisco genes in planta, that can eventually result in achieving efficient photosynthesis and increased crop productivity.