Precise isolation of high-quality RNA from leaves and storage roots of cassava ( Manihot esculenta Crantz) for gene expression studies

Background The isolation of Ribonucleic Acid (RNA) from leaves and storage roots of cassava ( Manihot esculenta Crantz) is a challenging one, due to the presence of large amounts of polyphenolic compounds, polysaccharides, and tuber proteins. RNA with high quality and intact integrity is vital for gene expression studies. We hereby report a precise, reproducible, and less cumbersome technique for isolating high-quality RNA from leaves and storage roots of cassava with minimal contamination from polyphenols, polysaccharides, and other secondary metabolites, using affordable reagents. This protocol functions without guanidinium salts in the extraction buffer. The presence of guanidinium salts usually leads to the formation of agglomerates during the extraction of RNA from plant tissues with high starch contents. Results The isolated RNA from leaves and storage roots of the ten cassava genotypes yielded between 1576.1 and 2861.9 µg/ml for RNA isolated from the leaf tissues and 2761.2–3873.5 µg/ml for RNA isolated from the storage roots. The A260:A280 ratios of the total RNA were more than 2.0 for both leaf and storage root samples, indicating minimal contamination from polysaccharides and polyphenols. The RNA samples recorded intact integrity, as demonstrated by clear 28 S and 18 S rRNA bands observed on agarose gel electrophoresis. The RNA integrity number (RIN) values ranged between 7.2 and 8.0. Also, the RNA samples were successfully used for transcriptome sequencing. Conclusion The present method which yielded high-quality and transcriptionally competent RNA samples is suitable for use in gene expression studies and downstream applications in the molecular breeding of cassava and related root/tuber crops.