ARS | Publication request: Chemical inhibition of ABA-8'-hydroxylase alters in vivo ABA metabolism, increases endogenous ABA content but does not affect microtuber dormancy

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: March 30, 2012
Publication Date: N/A

Technical Abstract: The effects of azole-type P450 inhibitors on in vitro ABA 8'-hydroxylase activity, in planta ABA metabolism, endogenous ABA content, and tuber meristem dormancy duration were examined in potato (Solanum tuberosum L. cv. Russet Burbank). When functionally expressed in yeast, three potato CYP707A genes were demonstrated to encode enzymatically active ABA 8'-hydroxylases with micro-molar affinities for (+)-ABA. The in vitro activity of the three enzymes was inhibited by the P450 azole-type inhibitors ancymidol, paclobutrazol, diniconazole, and tetcyclasis with diniconazole and tetcyclasis being the most potent inhibitors. The in planta metabolism of [3H]-(±)-ABA to phaseic acid and dihydrophaseic acid in tuber meristems was inhibited by diniconazole and tetcyclasis. Continuous exposure of in vitro generated microtubers to diniconazole resulted in a two-fold increase in endogenous ABA content and a decline in dihydrophaseic acid content after nine weeks of development. Tuber meristem dormancy progression was determined ex vitro in control and in DCN-treated microtubers following harvest. Sprouting percentages in control microtubers were 10, 17, 40, and 100 after 98 days, 114 days, 128 days, and 141 days, respectively. Continuous exposure to diniconazole during microtuber development had no effect on subsequent sprouting at any time point. The results indicate that, although a decrease in ABA content is a hallmark of tuber dormancy progression, the decline in ABA levels is not a prerequisite for dormancy exit and the onset of tuber sprouting.