Chemical inhibition of potato ABA-8'-hydroxylase activity alters in vitro and in vivo ABA metabolism and endogenous ABA levels but does not affect potato microtuber dormancy duration.
The effects of azole-type P450 inhibitors and two metabolism-resistant abscisic acid (ABA) analogues 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 micromolar affinities for (+)-ABA. The in vitro activity of the three enzymes was inhibited by the P450 azole-type inhibitors ancymidol, paclobutrazol, diniconazole, and tetcyclasis, and by the 8'-acetylene- and 8'-methylene-ABA analogues, with diniconazole and tetcyclasis being the most potent inhibitors. The in planta metabolism of [(3)H](±)-ABA to phaseic acid and dihydrophaseic acid in tuber meristems was inhibited by diniconazole, tetcyclasis, and to a lesser extent by 8'-acetylene- and 8'-methylene-ABA. Continuous exposure of in vitro generated microtubers to diniconazole resulted in a 2-fold increase in endogenous ABA content and a decline in dihydrophaseic acid content after 9 weeks of development. Similar treatment with 8'-acetylene-ABA had no effects on the endogenous contents of ABA or phaseic acid but reduced the content of dihydrophaseic acid. Tuber meristem dormancy progression was determined ex vitro in control, diniconazole-, and 8'-acetylene-ABA-treated microtubers following harvest. Continuous exposure to diniconazole during microtuber development had no effects on subsequent sprouting at any time point. Continuous exposure to 8'-acetylene-ABA significantly increased the rate of microtuber sprouting. 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.
US Department of Agriculture, Agricultural Research Service, Northern Crop Science Laboratory, 1605 Albrecht Blvd. N, Fargo, ND 58102-2765, USA. jeff.suttle@ars.usda.gov
Jeffrey C
JC
Suttle
Suzanne R
SR
Abrams
Luis
L
De Stefano-Beltrán
Linda L
LL
Huckle
D000040:Abscisic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006576:Heterocyclic Compounds, 4 or More Rings / Q000737:chemistry / Q000494:pharmacology; D018519:Meristem / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D010937:Plant Growth Regulators / Q000737:chemistry / Q000378:metabolism*; D010940:Plant Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D035281:Plant Tubers / Q000187:drug effects / Q000201:enzymology / Q000235:genetics / Q000502:physiology*; D011743:Pyrimidines / Q000494:pharmacology; D011198:Solanum tuberosum / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000502:physiology; D014230:Triazoles / Q000737:chemistry / Q000494:pharmacology
D065607:Cytochrome P-450 Enzyme Inhibitors; D006576:Heterocyclic Compounds, 4 or More Rings; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011743:Pyrimidines; D014230:Triazoles; C585342:tetcyclasis; C053577:ancymidol; C053370:paclobutrazol; D000040:Abscisic Acid; D003577:Cytochrome P-450 Enzyme System; C107203:abscisic acid 8'-hydroxylase; C049346:diniconazole