An efficient method for isolation of RNA and DNA from plants containing polyphenolics

Isolation of high quality RNA and DNA from plants especially cotton (Gossypium hirsutum; family Malvaceae) is notoriously difficult. This problem has been attributed to high content of phenolic terpenoids and tannins present in cotton cells (Katterman, and Shattuck, 1983). These compounds bind to RNA and DNA upon cell lysis and cannot be removed by conventional extraction procedures. Such RNA is not amenable to in vitro translation or cDNA cloning. We have encountered the same problem in many plants from family Malvaceae as well as from related family Bombacaceae. The methodology described here is a modified protocol of Chirgwin, etal., (1979) to include higher buffering capacity, alkaline pH, and most importantly poly vinyl pyrrolidone, which through hydrogen bonding, complexes with polyphenolics, effectively removing them from the homogenate. The homogenate is then subjected to ultracentrifugation to isolate RNA or DNA. The isolated RNA is suitable for cDNA cloning, in vitro translation or polymerase chain reaction.