Process for the production of plants with enhanced growth characteristics
View Patent ↗The invention is drawn to plant cell transformation with a nucleic acid construct comprising a prokaryotic ammonium-specific asparagine synthetase, type A, coding sequence, operably linked to a chloroplast transit peptide-encoding sequence, wherein said plant cells also contain a nucleic acid construct comprising a chloroplastic glutamine synthetase coding sequence in antisense orientation. Plant cells containing both nucleic acid constructs, and plants regenerated therefrom, exhibit improved growth characteristics.
1. A process for the production of plants with improved growth characteristics, which comprises the following steps:
a) transferring and integrating a nucleic acid encoding a polypeptide comprising an E. coli ammonium-specific asparagine synthetase, type A, linked to a chioroplast leader sequence for import of the asparagine synthetase into chloroplasts or plastids of a plant cell, wherein said nucleic acid is operatively linked to a regulatory sequence for expression in said plant cell;
b) transferring and integrating a nucleic acid for expression of an antisense chloroplastic glutamine synthetase RNA comprising transferring and integrating an anti-sense chloroplastic glutamine synthetase nucleic acid operatively linked to a regulatory sequence for expression of said anti-sense RNA in said cell to make a transformed cell; and
c) regenerating intact and fertile plants from the transformed cells, thereby producing plants with improved growth characteristics.
2. A plant cell obtainable by the method of claim 1 , comprising:
a) a nucleic acid encoding a polypeptide comprising an E. coli ammonium-specific asparagine synthetase, type A, linked to a chioroplast leader sequence for import of the asparagine synthetase into chloroplasts or plastids of a plant cell, wherein said nucleic acid is operatively linked to a regulatory sequence for expression in said plant cell; and
b) a second nucleic acid for expression of an anti-sense RNA to an endogenous chloroplastic glutamine synthetase gene comprising a nucleic acid comprising an endogenous chloroplastic glutamine sythetase in an anti-sense orientation operatively linked to a regulatory sequence, said second nucleic acid providing reduced levels of endogenous chloroplastic glutamine synthetase activity upon expression of said anti-sense RNA in said cell.
3. A plant, seed or propagule each containing a cell according to claim 2 .
4. A gene construct comprising:
(a) a nucleic acid encoding a polypeptide comprising an E. coli ammonium specific asparagine synthetase, type A, linked at its N-terminus to a chloroplastic leader peptide sequence for import of the E. coli ammonium-specific asparagine synthetase, type A, into the chloroplasts or plastids of a plant cell, wherein said nucleic acid is operatively linked to a regulatory sequence for expression in said plant cell, and
(b) a second nucleic acid for expression of an anti-sense sequence that encodes an RNA molecule that is complementary to an endogenous chloroplastic glutamine sythetase gene, operably linked to a regulatory sequence for expression of the anti-sense RNA in the plant cell.
5. A gene construct according to claim 4 , wherein the E. coli ammonium-specific asparagine synthetase, type A, polypeptide is linked at its N-terminus to a modified transit peptide having the amino acid sequence MASMISSSAVTTVSRASRGQSAAVASSSAVTTVSRASRGQAAVA(SEQ ID NO:5).
6. A vector comprising the gene construct according to claim 4 .
7. A plant cell transformed with the gene construct according to claim 4 or 5 , or with the vector according to claim 6 .