Web Release Date: February 9,
Extraction of RNA from Fresh, Frozen, and Lyophilized Tuber and Root Tissues
Postharvest Physiology and Biochemistry Lab, Department of Horticulture and Landscape Architecture, P.O. Box 646414, Washington State University, Pullman, Washington 99164-6414
Received for review October 12, 2006. Revised manuscript received December 18, 2006. Accepted January 3, 2007. Financial support provided by grants from the USDA/ARS and USDA/CSREES is gratefully acknowledged.
Abstract:
A method for isolating trancriptionally competent RNA from fresh, frozen, and lyophilized plant storage
tissues containing high levels of starch and phenolics is described. The protocol avoids the use of
guanidium salts, which often lead to the formation of a viscous gel during extraction of high starch-containing tissues, and instead uses a borate-Tris buffer in combination with high concentrations of
NaCl, Na2SO3, and sodium dodecyl sulfate in the extraction medium. RNA was extracted from fresh,
frozen, and lyophilized tissues of potato tubers, storage roots of sweet potato, radish, and turnip,
and rhizomes of ginger. The yield of RNA from potato tubers averaged 281 
g g fresh weight-1 and
1584 g g dry weight-1 from frozen and lyophilized samples, respectively. A260/A230 ratios of potato
RNA extracts were 2.2 or greater, indicating minimal contamination by polyphenols and carbohydrates.
Similarly, A260/A280 ratios exceeded 1.9, demonstrating minimal contamination of the RNA by tuber
protein. While A260/A280 ratios of extracts from the other plant species were somewhat lower than
those for potato (average = 1.56 and 1.80 for fresh and lyophilized samples, respectively), A260/A230
ratios averaged more than 2.0, and the RNA extracted from fresh and lyophilized samples of all
species was intact, as demonstrated by denaturing agarose-formaldehyde gel electrophoresis. The
protocol yielded RNA suitable for downstream molecular applications involving reverse transcription-polymerase chain reaction from all five species. Transcriptionally competent RNA was also recovered
from lyophilized potato tuber tissue stored for 6 years (ambient temperature) by a simple modification
to the protocol involving extraction in cold acetone. Lyophilization can thus be used to preserve RNA
in high starch- and phenolic-containing plant tissues for studies on gene expression.
Keywords: Solanum tuberosum L.; potato; radish; turnip; ginger; RNA extraction; lyophilized tissue; RT-PCR; starch; polyphenols
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