Hormone Profiling and Pyrosequencing Data Help to Establish a Model for Paradormancy Regulation in Underground Adventitious Buds of Canada Thistle

Vegetative reproduction from underground adventitious buds on the root system of Canada thistle contributes to the spread and persistence of this invasive perennial weed. Paradormancy in these vegetative root buds allows escape from conventional control measures. To simulate tillage we sectioned roots of greenhouse propagated Canada thistle, which caused release of paradormancy in ~65% of the root fragments and induced new vegetative shoots by 14 d post-sectioning. To identify molecular networks associated with paradormancy release in underground vegetative buds, we used Roche 454 GS-FLX pyrosequencing to quantify transcript abundance in root fragments at 0, 1, 2, and 3 days post-sectioning. Of the 15232 unigenes identified, in silico data analyses confirmed a role for numerous genes associated with plant hormone signalling networks. To follow up on these results, we examined hormone profiles in root fragment during release of paradormancy, which identified changes in the levels of ABA and ABA metabolites, auxins, and cytokinins. A model based on our in silico analysis and hormone profiling data suggest that ABA metabolism/signaling is a key regulator of paradormancy maintenance and release in underground adventitious buds of Canada thistle.  This model proposes that ABA synthesis/signaling is regulated through FUS3 and is responsive to polar auxin transport and further suggests that GA signaling, through interactions with ABA/FUS3, is required for induction of cell division and vegetative outgrowth.