title: Differences in phosphatidic acid signalling and metabolism between ABA and GA treatments of barley aleurone cells.
abstract: Phosphatidic acid (PA) is the common lipid product in abscisic acid (ABA) and gibberellic acid (GA) response. In this work we investigated the lipid metabolism in response to both hormones. We could detect an in vivo phospholipase D activity (PLD, EC 3.1.4.4). This PLD produced [(32)P]PA (phosphatidic acid) rapidly (minutes) in the presence of ABA, confirming PA involvement in signal transduction, and transiently, indicating rapid PA removal after generation. The presence of PA removal by phosphatidate phosphatase 1 and 2 isoforms (E.C. 3.1.3.4) was verified in isolated aleurone membranes in vitro, the former but not the latter being specifically responsive to the presence of GA or ABA. The in vitro DGPP phosphatase activity was not modified by short time incubation with GA or ABA while the in vitro PA kinase - that allows the production of 18:2-DGPP from 18:2-PA - is stimulated by ABA. The long term effects (24 h) of ABA or GA on lipid and fatty acid composition of aleurone layer cells were then investigated. An increase in PC and, to a lesser extent, in PE levels is the consequence of both hormone treatments. ABA, in aleurone layer cells, specifically activates a PLD whose product, PA, could be the substrate of PAP1 and/or PAK activities. Neither PLD nor PAK activation can be monitored by GA treatment. The increase in PAP1 activity monitored after ABA or GA treatment might participate in the increase in PC level observed after 24 h hormone incubation.
authors: Química Biológica, FCEFQN, Universidad Nacional de Río Cuarto, X5804BYA Río Cuarto, Córdoba, Argentina. lvillasuso@exa.unrc.edu.ar
authors: Ana Laura
authors: AL
authors: Villasuso
authors: Maria A
authors: MA
authors: Di Palma
authors: Marta
authors: M
authors: Aveldaño
authors: Susana J
authors: SJ
authors: Pasquaré
authors: Graciela
authors: G
authors: Racagni
authors: Norma M
authors: NM
authors: Giusto
authors: Estela E
authors: EE
authors: Machado
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D011756:Diphosphates / Q000378:metabolism; D005875:Gibberellins / Q000494:pharmacology*; D005990:Glycerol / Q000031:analogs & derivatives / Q000378:metabolism; D001467:Hordeum / Q000187:drug effects / Q000378:metabolism*; D000073718:Pancreatitis-Associated Proteins; D010711:Phosphatidate Phosphatase / Q000378:metabolism; D010712:Phosphatidic Acids / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D011756:Diphosphates; D005875:Gibberellins; D000073718:Pancreatitis-Associated Proteins; D010712:Phosphatidic Acids; C000612141:REG3A protein, human; C408642:diacylglycerol pyrophosphate; D000040:Abscisic Acid; C007842:gibberellic acid; D010711:Phosphatidate Phosphatase; D005990:Glycerol