Treatment of Potatoes with 1,4-Dimethylnapthalene Results in Temporal Changes in Transcription

Potatoes are the third largest agricultural crop in the world.  Sprout control is critical for storage, and applications of sprout inhibitors have been used to maintain storage life of tubers.  Chlorpropham (CIPC) is the most common method to prevent sprouting; CIPC disrupts microtubules and there is concern regarding its impact on human health. The compound 1,4-dimethylnapthalene (DMN), originally isolated from dormant potato tubers, has been recently used as a sprout control agent in stored tubers.  To determine a possible mode of action for DMN changes, the potato transcriptomes were examined following application of the sprout inhibitor. Nondormant potato tubers were treated in a 9 L air tight chamber with concentrations of DMN ranging from 19.5 µmol/L to 1625 µmol/L.  Potato periderm and meristems were harvested after two days of DMN application and after five days of air-dry time.  Harvested meristems were frozen in liquid nitrogen, RNA was extracted, and a cDNA library was produced.  The average periderm residue levels for DMN ranged from 0.1 to 4.2 ppm depending on the level of exposure.  Transcripts were mapped to the doubled monohaploid S. tuberosum DM1-3 using Tophat. Differential expression was determined using Cufflinks. QT-PCR was utilized to confirm RNA-seq data and showed that the WRKY transcription factors are altered under DMN exposure with varying levels of increasing, decreasing, and maintaining levels of expression. Several transcripts associated with plastid function and development decreased. Both the WRKY and plastid genes showed recovery 14 days after DMN exposure to normal levels.