System for capturing and modifying large pieces of genomic DNA and constructing organisms with synthetic chloroplasts
The functional analysis of genes frequently requires the manipulation of large genomic regions. A yeast-bacteria shuttle vector is described that can be used to clone large regions of DNA by homologous recombination. Also described is a method for isolating entire genomes, including chloroplast genomes, or large portions thereof, and manipulating the same. Also described are methods for determining minimal genomes, minimal pathway requirements, and minimal organelle genomes.
1 . A method of producing a vector containing a reconstructed genome, comprising
(a) introducing two or more vectors into a host cell, wherein said vectors comprise fragments of a genome
(b) recombining said vectors into a single vector comprising at least about 90% of a genome, thereby producing a reconstructed genome.
2 . The method of claim 1 , wherein said reconstructed genome has at least one modification.
3 . The method of claim 2 , wherein said modification is made by homologous recombination in a yeast cell using a targeted integration vector.
4 . The method of claim 3 , wherein said targeted integration vector comprises a segment containing the modification to be introduced and two targeting segments of 40 to 1000 bases on each end of the integration vector.
5 . The method of claim 4 , wherein the targeted integration vector is produced using the polymerase chain reaction and said targeting segments are from about 40 bases to about 200 bases.
6 . The method of claim 5 , wherein said targeted integration vector is made using a set of primers, each primer comprising an area of 18 to 20 bases identical to the segment of modified DNA and an area of about 40 to 200 bases identical to the targeted integration site.
7 . The method of claim 2 , wherein said at least one modification comprises an addition, deletion, mutation or rearrangement.
8 . The method of claim 1 , wherein said fragments of the genome are obtained from a non vascular photosynthetic organism.
9 . The method of claim 8 , wherein said photosynthetic organism is a microalgae or a macroalgae.
10 . The method of claim 8 , wherein said photosynthetic organism is selected from the group consisting of Ch. Vulgaris, C. reinhardtii, D. salina, S. quadricanda and H. pluvalis.
11 . The method of claim 2 , wherein said at least one modification introduces an exogenous coding region.
12 . The method of claim 11 , wherein said exogenous coding region encodes an enzyme in a pathway for synthesis of a fatty acid, a terpene or a terpenoid.
13 . A plant comprising a reconstituted genome of claim 1 .
14 . The plant of claim 13 , wherein said plant is a non-vascular photosynthetic organism.
15 . The plant of claim 14 , wherein the non-vascular photosynthetic organisms is a microalgae or a macroalgae.
16 . The plant of claim 14 , wherein the non-vascular photosynthetic organisms is selected from the group consisting of Ch. vulgaris, C. reinhardtii D. salina, S. quadricanda and H. pluvalis.
17 . The plant of claim 13 , wherein said plant is non-photosynthetic.
18 . The plant of claim 17 , wherein said plant is non-photosynthetic due to a natural or induced mutation.
19 . The plant of claim 17 , wherein said plant is made photoautotrophic by the presence of the synthetic chloroplast genome.
20 . A method for stabilizing and or modifying one or more target regions of DNA comprising:
obtaining a DNA cassette comprising a selection marker, a heterologous DNA sequence or both;
obtaining a set of primers, said primers comprising in a 5′ to 3′ order, approximately 40-200 nucleotides identical to a sequence in a target region to be modified and 18 to 20 nucleotides identical to a 3′ end sequence of the DNA cassette;
amplifying the DNA cassette by polymerase chain reaction to produce an insertion vector comprising the DNA cassette flanked by nucleotide sequences identical to the target region to be modified or stabilized; and
inserting said insertion vector into the target region of DNA by homologous recombination.
21 . The method of claim 20 , wherein said primers comprise, in a 5′ to 3′ order, approximately 40-60 nucleotides identical to a sequence in the target region to be modified and 18 to 20 nucleotides identical to a 3′ end sequence of the DNA cassette.