Microarray based multiplex pathogen analysis and uses thereof
First Claim
1. A method for quantitating copy number of DNA for one or more pathogens in a plant sample comprising the steps of:
- a) harvesting pathogens from a plant tissue sample;
b) isolating total nucleic acids comprising DNA and non-DNA nucleic acids from the pathogens harvested from the plant tissue sample;
c) adding a known copy number of at least one synthetic DNA sequence as an internal reference standard to the total nucleic acids, each of said synthetic DNA sequence comprising;
a central region having a nucleotide sequence distinct from signature sequence determinants in the pathogen DNA; and
a 5′
end and a 3′
end having nucleotide sequences substantially identical to a consensus sequence in the pathogen DNA;
d) amplifying, in a first amplification in tandem in a single assay the pathogen DNA and the at least one synthetic DNA sequence in the total nucleic acids using at least one first primer pair selective for the pathogen DNA and the synthetic DNA sequence to generate one or more pathogen DNA-specific first amplicons and one or more synthetic DNA-specific second amplicons;
e) amplifying, in a second amplification in tandem using the one or more pathogen DNA-specific first amplicons and the one or more synthetic DNA-specific second amplicons as a template and at least one first fluorescent labeled second primer pair to generate pathogen DNA-specific first fluorescent labeled third amplicons and synthetic DNA-specific first fluorescent labeled fourth amplicons;
f) hybridizing the pathogen DNA-specific first fluorescent labeled third amplicons and the synthetic DNA-specific first fluorescent labeled fourth amplicons with nucleic acid probes specific for signature sequence determinants in the pathogen DNA and the synthetic DNA central region sequences respectively, said nucleic acid probes immobilized at specific known positions on a 3-dimensional lattice microarray via second fluorescent labeled bifunctional polymer linkers;
g) washing the 3-dimensional lattice microarray at least once;
h) imaging the 3-dimensional lattice microarray to detect a first fluorescent signal corresponding to the pathogen DNA-specific first fluorescent labeled third amplicons and the synthetic DNA-specific first fluorescent labeled fourth amplicons, and a second fluorescent signal corresponding to the nucleic acid probes immobilized at the specific known positions on the microarray via the second fluorescent labeled bifunctional polymer linkers;
i) superimposing the first fluorescent signal on the second fluorescent signal to obtain a superimposed signal image;
j) comparing the sequence of the nucleic acid probe at one or more superimposed signal positions on the 3-dimensional lattice microarray with a database of signature sequence determinants for a plurality of pathogen DNA thereby identifying the pathogens in the sample; and
k) correlating mathematically, a fluorescent signal intensity from the pathogen DNA-specific first fluorescent labeled third amplicons with a fluorescent signal intensity from the synthetic DNA-specific first fluorescent labeled fourth amplicons and the known copy number of the synthetic DNA sequence, thereby quantitating copy number of the pathogen DNA in the sample.
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Abstract
Provided herein is an internal standard method for determining copy number of a pathogen DNA in an unpurified nucleic acid sample by using a known copy number of synthetic DNA that shares a consensus region sequence with the pathogen. The sample is subject to two amplification steps using locus-specific primers and fluorescent primers respectively to obtain fluorescent amplicons for the pathogen and synthetic DNA. These are hybridized with immobilized pathogen-specific and synthetic DNA-specific nucleic acid probes and imaged to obtain fluorescent signals for pathogen-specific and synthetic DNA-specific amplicons. Signal intensities are correlated with the known copy number of synthetic DNA to determine copy number of pathogen DNA in the plant. Also described herein is a method to simultaneously quantitate using the above method, copy numbers of both pathogen and plant DNA in a sample.
1 Citation
13 Claims
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1. A method for quantitating copy number of DNA for one or more pathogens in a plant sample comprising the steps of:
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a) harvesting pathogens from a plant tissue sample; b) isolating total nucleic acids comprising DNA and non-DNA nucleic acids from the pathogens harvested from the plant tissue sample; c) adding a known copy number of at least one synthetic DNA sequence as an internal reference standard to the total nucleic acids, each of said synthetic DNA sequence comprising; a central region having a nucleotide sequence distinct from signature sequence determinants in the pathogen DNA; and a 5′
end and a 3′
end having nucleotide sequences substantially identical to a consensus sequence in the pathogen DNA;d) amplifying, in a first amplification in tandem in a single assay the pathogen DNA and the at least one synthetic DNA sequence in the total nucleic acids using at least one first primer pair selective for the pathogen DNA and the synthetic DNA sequence to generate one or more pathogen DNA-specific first amplicons and one or more synthetic DNA-specific second amplicons; e) amplifying, in a second amplification in tandem using the one or more pathogen DNA-specific first amplicons and the one or more synthetic DNA-specific second amplicons as a template and at least one first fluorescent labeled second primer pair to generate pathogen DNA-specific first fluorescent labeled third amplicons and synthetic DNA-specific first fluorescent labeled fourth amplicons; f) hybridizing the pathogen DNA-specific first fluorescent labeled third amplicons and the synthetic DNA-specific first fluorescent labeled fourth amplicons with nucleic acid probes specific for signature sequence determinants in the pathogen DNA and the synthetic DNA central region sequences respectively, said nucleic acid probes immobilized at specific known positions on a 3-dimensional lattice microarray via second fluorescent labeled bifunctional polymer linkers; g) washing the 3-dimensional lattice microarray at least once; h) imaging the 3-dimensional lattice microarray to detect a first fluorescent signal corresponding to the pathogen DNA-specific first fluorescent labeled third amplicons and the synthetic DNA-specific first fluorescent labeled fourth amplicons, and a second fluorescent signal corresponding to the nucleic acid probes immobilized at the specific known positions on the microarray via the second fluorescent labeled bifunctional polymer linkers; i) superimposing the first fluorescent signal on the second fluorescent signal to obtain a superimposed signal image; j) comparing the sequence of the nucleic acid probe at one or more superimposed signal positions on the 3-dimensional lattice microarray with a database of signature sequence determinants for a plurality of pathogen DNA thereby identifying the pathogens in the sample; and k) correlating mathematically, a fluorescent signal intensity from the pathogen DNA-specific first fluorescent labeled third amplicons with a fluorescent signal intensity from the synthetic DNA-specific first fluorescent labeled fourth amplicons and the known copy number of the synthetic DNA sequence, thereby quantitating copy number of the pathogen DNA in the sample. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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Specification