Efficient Isolation of High-quality Total RNA from Strawberry

Abstract

Sufficient yields of high-quality RNA are needed for next-generation sequencing and high-throughput real-time polymerase chain reaction analyses. In the case of strawberry (Fragaria ×ananassa) fruits, successful RNA isolation requires removal of abundant inhibitory substances (polysaccharides and polyphenols) that greatly reduce quality and yield. In this study, we applied various combinations of RNA isolation protocols directed at reproductive organs. The best manual isolation method involved nonionic polymer and modified acid guanidinium thiocyanate-phenol-chloroform treatments followed by phenol/chloroform/isoamyl alcohol extraction. Compared with other methods, this approach gave significantly higher yields [84.0 µg/g fresh weight (FW)] of RNA of greater purity (A260/A280 = 1.99; A260/230 = 1.51). Better-quality RNA (A260/230 = 2.11) was obtained using an automated method, but the yield was lower (18.1 µg/g FW) than that obtained manually. This automated method consisted of pretreatment with nonionic polymer followed by a silica-based system extraction. Although RNA of sufficient quality [RNA Integrity Number (RIN) ≥ 6.5 and 28S/18S ≥ 1.0] for RNA sequencing was obtained from receptacles using both automated and manual methods, the manual method yielded high-quality RNA from achenes and anthers. The automatic method features 6-fold faster high-throughput capacity, whereas the manual method has wider applicability to different tissues.