Methods and vectors for producing transgenic plants
Methods of, and compositions for, assembling one or more transcription units in a genome without a linked selectable marker or other unwanted transcription unit are provided. Also provided methods of, and compositions for, assembling one or more transcription units in a genome with a reduced frequency of vector backbone.
1. A nucleic acid molecule comprising
a first DNA segment comprising a first transcription unit located between a first left T-DNA border region and a first right T-DNA border region, wherein at least one of said first left T-DNA border region and said first right T-DNA border region is flanked on both sides by and adjacent to a first and a second shorter transcribable nucleic acid sequence in opposite orientation to each other,
wherein said first and second shorter transcribable nucleic acid sequences are homologous to a portion of a sequence of interest within said first transcription unit, and wherein said T-DNA border regions are capable of enabling the transfer of said segment into a genome;
wherein each shorter transcribable nucleic acid sequence is at least 21 nucleotides long and comprises at least 21 contiguous nucleotides of the sequence of interest.
2. The nucleic acid molecule of claim 1 , wherein said first and second shorter transcribable nucleic acid sequences are operably linked to form a transcription unit.
3. The nucleic acid molecule of claim 1 , further comprising a promoter operably linked to said first or second shorter transcribable nucleic acid sequence.
4. The nucleic acid molecule of claim 1 , wherein said first or second shorter transcribable nucleic acid sequence is operably linked to said first transcription unit.
5. The nucleic acid molecule of claim 1 , wherein said first transcription unit does not comprise a termination sequence.
6. The nucleic acid molecule of claim 1 , wherein said first and second shorter transcribable nucleic acid sequences are each at least 75 nucleotides in length.
7. The nucleic acid molecule of claim 1 , wherein said first transcription unit comprises a selectable marker gene.
8. The nucleic acid molecule of claim 7 , wherein said first and second shorter transcribable nucleic acid sequences are non-natural sequences.
9. The nucleic acid molecule of claim 1 , further comprising a second DNA segment comprising a second transcription unit located between a second left T-DNA border region and a second right T-DNA border region, wherein at least one of said second left T-DNA border region and said second right T-DNA border region is flanked on both sides by and adjacent to a third and a fourth shorter transcribable nucleic acid sequence in opposite orientation to each other, and wherein said third and fourth shorter transcribable nucleic acid sequences are homologous to a portion of said sequence of interest within said first transcription unit;
wherein each shorter transcribable nucleic acid sequence is at least 21 nucleotides long and comprises at least 21 contiguous nucleotides of the sequence of interest.
10. A method comprising:
a. transforming a plant cell with a nucleic acid molecule comprising a first DNA segment comprising a first transcription unit located between a first left T-DNA border region and a first right T-DNA border region, wherein at least one of said first left T-DNA border region and said first right T-DNA border region is flanked on both sides by and physically linked to a first and a second shorter transcribable nucleic acid sequence in opposite orientation to each other,
wherein said first and second shorter transcribable nucleic acid sequences are homologous to a portion of said first transcription unit;
b. growing said transformed plant cell; and
c. selecting a transgenic plant cell which expresses a sequence of interest within said first transcription unit;
wherein each shorter transcribable nucleic acid sequence is at least 21 nucleotides long and comprises at least 21 contiguous nucleotides of the first transcription unit.
11. The nucleic acid molecule of claim 1 , wherein said first and second shorter transcribable nucleic acid sequences are capable of being transcribed into a single RNA molecule.
12. The nucleic acid molecule of claim 1 , wherein said sequence of interest is a nucleic acid sequence that causes the targeted expression or over-expression of an exogenous nucleic acid sequence.
13. The nucleic acid molecule of claim 1 , wherein said sequence of interest is a protein coding sequence.
14. The nucleic acid molecule of claim 1 , wherein said sequence of interest causes the inhibition of expression of an endogenous gene via gene silencing.
15. The method of claim 10 , wherein said plant cell is a sugarcane, wheat, corn, soybean, cotton, or canola plant cell.
16. The method of claim 10 , wherein said transforming is achieved through a bacterial cell selected from the group consisting of Agrobacterium spp., Rhizobium spp., Sinorhizobium spp., Mesorhizobium spp., Phyllobacterium spp., Ochrobactrum spp., and Bradyrhizobium spp.
17. The method of claim 10 , wherein said first and second shorter transcribable nucleic acid sequences are operably linked to form a transcription unit.
18. The method of claim 10 , wherein said first and second shorter transcribable nucleic acid sequences are capable of being transcribed into a single RNA molecule.
19. The method of claim 10 , wherein said first transcription unit comprises a selectable marker gene.
20. The method of claim 10 , wherein said first and second shorter transcribable nucleic acid sequences are non-natural sequences.
21. The method of claim 10 , wherein said first and second shorter transcribable nucleic acid sequences are homologous to a portion of a sequence of interest within said first transcription unit.
22. The method of claim 21 , wherein said sequence of interest is a protein coding sequence.