Northern and Southern blot detections of MT-1 and MT-II genes. A. Samples (10 μg) of genomic DNA from sweet potato Tainong 57 leaves were digested with Eco RI (E), Bam HI (B), and Hind III (H). The DNA fragments were separated in 0.8% agarose gels, transferred to a Hybond- N-nylon membrane, and hybridized with PCR-labeled cDNA probes. Molecular size markers were λ DNA/Hind III fragments. B. Northern blot analysis. Samples (10 μg each) of total RNA were isolated from different tissues of sweet potato and actin (AY905538) was utilized as an internal control of mRNA from sweet potato. Blots were hybridized to α-32P-labeled 3′ specific cDNA probes. Lane 1: storage roots, lane 2: sprout, lane 3: veins, lane 4: sprouted roots, and lane 5: full expanded green leaves. Actin was used as a control. The experiments were done twice and a representative one was shown.