A simple protocol for RNA isolation from fruit trees containing high levels of polysaccharides and polyphenol compounds

RNA isolation is a prerequisite to the study of gene expression at the molecular level and has an increasingly important role in physiological and genetic investigations of fruit trees. However, RNA isolation is difficult in fruit trees that contain large amounts of polysaccharides and polyphenol compounds. Until now, no commercial kit has been developed specifically for the isolation of high-quality RNA from fruit trees. Furthermore, because of the large amounts of polysaccharides and polyphenol compounds, the common protocols for RNA isolation are tedious and usually result in poor yields when applied to kiwifruit, apples, and peaches. Here we describe a simple method for RNA isolation from fruit trees. This procedure involves easy grinding by zirconia balls; washing the fruit samples before extraction; extraction of RNA; and removal of proteins, polyphenols, and polysaccharides by insoluble polyvinylpyrrolidone (PVP) and potassium acetate with ethanol. The protocol results in high-quality RNA, as evidenced by performing reverse transcription-polymerase chain reaction (RT-PCR) and northern blot analysis.