Interactions among LOX metabolites regulate temperature-mediated flower bud formation in morning glory (Pharbitis nil).
We examined the relationship between temperature (15-35°C) and flower induction as it is influenced by linolenic acid (LA) cascade products, lipoxygenase (LOX; EC 1.13.11.12), allene oxide synthase (AOS; EC 4.2.1.92), and allene oxide cyclase (AOC; EC 5.3.99.6) generated in morning glory (Pharbitis nil Choisy). The maximum amount of LOX protein was detected when plants were grown at 30°C, whereas endogenous AOS and AOC proteins were markedly accumulated at 15°C. Although both test levels of 9(S)- and 13(S)-hydroperoxy linolenic acid (HPOT) showed similar temperature dependencies, reflecting the profile of LOX, the relative amount of 13(S)-HPOT was much higher than that of 9(S)-HPOT, regardless of temperature regime. This implied a faster reaction pathway to 9,10-α-ketol octadecadienoic acid (KODA) in the LA cascade. In the 13(S)-HPOT pathway, the highest level of endogenous jasmonic acid (JA) was observed at 15°C. Our results suggest that at a high temperature (30°C), 9(S)-HPOT may be readily metabolized into KODA to promote flower bud formation. By contrast, at a low temperature, high levels of AOS and AOC result in an accumulation of JA that inhibits this developmental process. Accordingly, depending on the growing temperature, flower bud formation in P. nil is possibly regulated by the interactions among LOX metabolites, with KODA serving as a promoter and JA as an inhibitor.
Laboratory of Bio-organic Chemistry, Division of Applied Bioscience, Graduate School of Agriculture, Hokkaido University, Kita 9, Nishi 9, Kitaku, Sapporo 060-8589, Japan.
Kyong-Hee
KH
Nam
Teruhiko
T
Yoshihara
D003510:Cyclohexanes / Q000378:metabolism; D003517:Cyclopentanes / Q000378:metabolism* / Q000494:pharmacology; D004852:Epoxy Compounds / Q000378:metabolism; D035264:Flowers / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D019746:Intramolecular Oxidoreductases / Q000235:genetics / Q000378:metabolism; D049915:Ipomoea nil / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D008084:Lipoxygenase / Q000235:genetics / Q000378:metabolism*; D054883:Oxylipins / Q000378:metabolism* / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000378:metabolism* / Q000494:pharmacology; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D015398:Signal Transduction; D013696:Temperature; D017962:alpha-Linolenic Acid / Q000031:analogs & derivatives / Q000737:chemistry / Q000378:metabolism*
D003510:Cyclohexanes; D003517:Cyclopentanes; D004852:Epoxy Compounds; D054883:Oxylipins; D010937:Plant Growth Regulators; C496818:theobroxide; D017962:alpha-Linolenic Acid; C011006:jasmonic acid; D008084:Lipoxygenase; D019746:Intramolecular Oxidoreductases; C021377:hydroperoxide isomerase