| Title | Diacylglycerol pyrophosphate inhibits the alpha-amylase secretion stimulated by gibberellic acid in barley aleurone. | | Author(s) | Racagni G, Villasuso AL, Pasquaré SJ, Giusto NM, Machado E | | Institution | Química Biológica, FCEFQN, Universidad Nacional de Río Cuarto, X5804BYA Río Cuarto, Córdoba, Argentina. | | Source | Physiol Plant 2008 Jun 19. | | Abstract | Abscisic acid (ABA) plays an important regulatory role in seed germination since it inhibits the response to gibberellic acid (GA) in aleurone, a secretory tissue surrounding the endosperm. Phosphatidic acid (PA) is a well-known intermediary in ABA signalling, but the role of diacylglycerol pyrophosphate (DGPP) in germination processes is not clearly established. We show here that PA produced by phospholipase D (PLD) (E.C. 3.1.4.4) during the antagonist effect of ABA in GA signalling is rapidly phosphorylated by phosphatidate kinase (PAK) to DGPP. This is a crucial fact for aleurone function, since exogenously added dioleoyl-DGPP inhibits secretion of alpha-amylase (E.C. 3.2.1.1). Aleurone treatment with ABA and 1-butanol results in normal secretory activity, and this effect is reversed by addition of dioleoyl-DGPP. We also found that ABA decreased the activity of an Mg(2+)-independent, NEM-insensitive form of phosphatidate phosphohydrolase (PAP2) (E.C. 3.1.3.4), leading to reduction of PA dephosphorylation and increased PAK activity. Sequence analysis using Arabidopsis thaliana lipid phosphate phosphatase (Lpp) sequences as queries identified two putative molecular homologues, termed HvLPP1 and HvLPP2, encoding putative Lpps with the presence of well conserved structural Lpp domains. Our results are consistent with a role of DGPP as a regulator of ABA antagonist effect in GA signalling, and provide evidence about regulation of PA level by a PAP2 during ABA response in aleurone. | | Language | ENG | | Pub Type(s) | JOURNAL ARTICLE
| | PubMed ID | 18573189 |
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