An improved method for high-quality RNA isolation from needles of adult maritime pine trees

When conventional RNA isolation methods optimized for pine seedlings are applied to needles of adult pine trees, poor-quality RNA results. Here we describe a modified procedure to isolate high-quality RNA from needles of 30-year-old maritime pines, exhibiting high levels of phenolics, polysaccharides, and RNases. Major changes are the inclusion of proteinase K in the extraction medium followed by incubation at 42degreesC. Integrity and purity were evaluated by using denaturing gel electrophoresis and spectrophotometry (A(260)/A(230) and A(260)/A(280)). The total RNA Could be successfully used for poly(A)(+)-RNA isolation and cDNA library construction.