Verification of the miRNA targeting Cf-9
Tomato genomic DNA was extracted using Plant DNAzol reagents
(Life Science, China) following the procedure recommended
by the manufactory. Pri-miRNA sequence of the predicted miRNA
was amplified from tomato genomic DNA while cDNA sequence of
its potential target gene Cf-9 was amplified from tomato cDNA with
the primers listed at Table 1, which were then cloned into binary
vector pCHF3 with Kpn I/Sal I and BamH I/Sal I, respectively, to
release the recombinant constructs pCHF3::pri-miRNA and
pCHF3::Cf-9. These recombinant plasmids and the empty plasmid
as a control were transformed into Agrobacterium tumefaciens
strain GV3101. Mixtures at 1:1 ratio of Agrobacterium suspensions
carrying pCHF3::Cf-9 and those containing pCHF3::pri-miRNA or
pCHF3 empty vector with a final OD600 of 2.0 for each type of
bacteria were prepared as described [19,20], and were infiltrated
into Nicotiana benthamiana leaves using needleless syringes. For
assays in Cf-9 tomato plants, solely Agrobacterium suspensions
carrying pCHF3::pri-miRNA or pCHF3 empty vector as a control
were infiltrated into tomato leaves. After infiltration, the plants
were grown at 25 C. Expression of the Cf-9 gene in the agroinfiltrated
areas was detected by RT-qPCR at 3 d post infiltration