Polyamine metabolism is altered in unpollinated parthenocarpic pat-2 tomato ovaries.
Facultative parthenocarpy induced by the recessive mutation pat-2 in tomato (Lycopersicon esculentum Mill.) depends on gibberellins (GAs) and is associated with changes in GA content in unpollinated ovaries. Polyamines (PAs) have also been proposed to play a role in early tomato fruit development. We therefore investigated whether PAs are able to induce parthenocarpy and whether the pat-2 mutation alters the content and metabolism of PAs in unpollinated ovaries. Application of putrescine, spermidine, and spermine to wild-type unpollinated tomato ovaries (cv Madrigal [MA/wt]) induced partial parthenocarpy. Parthenocarpic growth of MA/pat-2 (a parthenocarpic near-isogenic line to MA/wt) ovaries was negated by paclobutrazol (GA biosynthesis inhibitor), and this inhibition was counteracted by spermidine. Application of alpha-difluoromethyl-ornithine (-Orn) and/or alpha-difluoromethyl-arginine (-Arg), irreversible inhibitors of the putrescine biosynthesis enzymes Orn decarboxylase (ODC) and Arg decarboxylase, respectively, prevented growth of unpollinated MA/pat-2 ovaries. Alpha-difluoromethyl-Arg inhibition was counteracted by putrescine and GA(3), whereas that of alpha-difluoromethyl-Orn was counteracted by GA(3) but not by putrescine or spermidine. In unpollinated MA/pat-2 ovaries, the content of free spermine was significantly higher than in MA/wt ovaries. ODC activity was higher in pat-2 ovaries than in MA/wt. Transcript levels of genes encoding ODC and spermidine synthase were also higher in MA/pat-2. All together, these results strongly suggest that the parthenocarpic ability of pat-2 mutants depends on elevated PAs levels in unpollinated mutant ovaries, which correlate with an activation of the ODC pathway, probably as a consequence of elevated GA content in unpollinated pat-2 tomato ovaries.
Fos
Mariano
M
Departmento de Biología Vegetal, Universidad Politécnica de Valencia, 46022-Valencia, Spain. mfos@bvg.upv.es
Proaño
Karina
K
Alabadí
David
D
Nuez
Fernando
F
Carbonell
Juan
J
García-Martínez
José L
JL
D002262:Carboxy-Lyases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D000518:Eflornithine / Q000494:pharmacology; D035264:Flowers / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism; D005638:Fruit / Q000254:growth & development; D005875:Gibberellins / Q000378:metabolism* / Q000494:pharmacology; D018551:Solanum lycopersicum / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D009154:Mutation; D009955:Ornithine Decarboxylase / Q000235:genetics / Q000378:metabolism; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines / Q000037:antagonists & inhibitors / Q000378:metabolism* / Q000494:pharmacology; D011700:Putrescine / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology; D018749:RNA, Plant / Q000235:genetics / Q000378:metabolism; D012098:Reproduction / Q000502:physiology; D013095:Spermidine / Q000378:metabolism / Q000494:pharmacology; D011436:Spermidine Synthase / Q000235:genetics / Q000378:metabolism; D013096:Spermine / Q000378:metabolism / Q000494:pharmacology; D014230:Triazoles / Q000494:pharmacology
D005875:Gibberellins; D065108:Ornithine Decarboxylase Inhibitors; D011073:Polyamines; D018749:RNA, Plant; D014230:Triazoles; D013096:Spermine; C053370:paclobutrazol; C007842:gibberellic acid; D011436:Spermidine Synthase; D002262:Carboxy-Lyases; D009955:Ornithine Decarboxylase; C019722:arginine decarboxylase; D013095:Spermidine; D011700:Putrescine; D000518:Eflornithine