Disease cycle of potato late blight - MSpace at the University of ...

1 mM DTT, pH 7.9 ), 0.2 mM of dNTP mix, 5 U/μl of E. coli DNA Ligase, 20 U/μl of E.
coli DNA polymerase and 5 U/μl of E. coli RNAse H. The reaction was completed with
water to 150 μl and incubated for 2h at 16ºC in a thermocycler (Techne Flexigene, Inc.,
Canada). The reaction was transferred into a 1.5 ml tube, the reaction mixture was
removed by pipetting, and the double-stranded cDNA was collected using a magnetic
separation stand. Then, the double-stranded cDNA was re-suspended in 50 μl of sterile
water and boiled for 10 min to denature the cDNA. Without delay, using a magnetic
separation stand, the second-strand cDNA (supernatant) was separated from the first-
strand (collected particles). The first-strand cDNA from the non-inoculated plant (control)
was combined with 18 μl of the second-strand cDNA (inoculated plant) in 30 μl of
hybridization buffer (30 mM HEPES, 1 mM EDTA, 1 M NaCl). The mixture was
incubated for 24 h at 37°C. At the end of the incubation, 3 cDNA species were present in
the mixture: (i) un-hybridized cDNA from non-inoculated plants (attached to magnetic
beads), (ii) hybridized cDNA from non-inoculated and inoculated plants (attached to
magnetic beads) and (iii) un-hybridized cDNA from inoculated plants was in the
supernatant (no magnetic beads). The latter is the SH product selected (transcripts of
interest) that was precipitated with 3 volumes of isopropanol, washed with 70% ethanol
and dissolved in a final volume of 20 μl of sterile water. In addition, for each genotype of
P. infestans, the same procedures described above for first and second strands were used
without hybridization. Finally, a 2-μl aliquot from products of interest was visualized in a
1.2 % Petri dish agarose gel with Et-Br in order to corroborate the presence of cDNA.
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