Protocols for dry DNA storage and shipment at room temperature

The globalization of DNA barcoding will require core analytical facilities to develop cost-effective, efficient protocols for the shipment and archival storage of DNA extracts and PCR products. We evaluated three dry-state DNA stabilization systems: commercial Biomatrica((R)) DNAstable((R)) plates, home-made trehalose and polyvinyl alcohol (PVA) plates on 96-well panels of insect DNA stored at 56 degrees C and at room temperature. Controls included unprotected samples that were stored dry at room temperature and at 56 degrees C, and diluted samples held at 4 degrees C and at -20 degrees C. PCR and selective sequencing were performed over a 4-year interval to test the condition of DNA extracts. Biomatrica((R)) provided better protection of DNA at 56 degrees C and at room temperature than trehalose and PVA, especially for diluted samples. PVA was the second best protectant after Biomatrica((R)) at room temperature, whereas trehalose was the second best protectant at 56 degrees C. In spite of lower PCR success, the DNA stored at -20 degrees C yielded longer sequence reads and stronger signal, indicating that temperature is a crucial factor for DNA quality which has to be considered especially for long-term storage. Although it is premature to advocate a transition to DNA storage at room temperature, dry storage provides an additional layer of security for frozen samples, protecting them from degradation in the event of freezer failure. All three forms of DNA preservation enable shipment of dry DNA and PCR products between barcoding facilities.