CONICET | Buscador de Institutos y Recursos Humanos

For Peer Review 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 3 endosperm. Phosphatidic acid (PA) is a well-known intermediary in ABA signalling, but 4 the role of diacylglycerol pyrophosphate (DGPP) in germination processes is not clearly 5 established. We show here that PA produced by phospholipase D (PLD) (E.C. 3.1.4.4) 6 during the antagonist effect of ABA in GA signalling is rapidly phosphorylated by 7 phosphatidate kinase (PAK) to DGPP. This is a crucial fact for aleurone function, since 8 exogenously added dioleoyl-DGPP inhibits secretion of -amylase (E.C. 3.2.1.1). Blocking 9 of PLD activity by 1-butanol during ABA treatment results in normal secretory activity, 10 and this effect is reversed by addition of dioleoyl-DGPP. We also found that ABA 11 decreased the activity of an Mg2+-independent, NEM-insensitive form of phosphatidate 12 phosphohydrolase (PAP2) (E.C. 3.1.3.4), leading to reduction of PA dephosphorylation and 13 increased PAK activity. Sequence analysis using Arabidopsis thaliana lipid phosphate 14 phosphatase (Lpp) sequences as queries identified two putative molecular homologues, 15 termed HvLPP1 and HvLPP2, encoding putative Lpps. The presence of well conserved 16 structural Lpp domains in these sequences, and the detection of proteins by 17 immunoblotting, suggest that both proteins are functional enzymes. Our results are 18 consistent with a role of DGPP as a regulator of ABA antagonist effect in GA signalling, 19 and provide evidence about regulation of PA level by a PAP2 during ABA response in 20 aleurone. 21 22-amylase (E.C. 3.2.1.1). Blocking 9 of PLD activity by 1-butanol during ABA treatment results in normal secretory activity, 10 and this effect is reversed by addition of dioleoyl-DGPP. We also found that ABA 11 decreased the activity of an Mg2+-independent, NEM-insensitive form of phosphatidate 12 phosphohydrolase (PAP2) (E.C. 3.1.3.4), leading to reduction of PA dephosphorylation and 13 increased PAK activity. Sequence analysis using Arabidopsis thaliana lipid phosphate 14 phosphatase (Lpp) sequences as queries identified two putative molecular homologues, 15 termed HvLPP1 and HvLPP2, encoding putative Lpps. The presence of well conserved 16 structural Lpp domains in these sequences, and the detection of proteins by 17 immunoblotting, suggest that both proteins are functional enzymes. Our results are 18 consistent with a role of DGPP as a regulator of ABA antagonist effect in GA signalling, 19 and provide evidence about regulation of PA level by a PAP2 during ABA response in 20 aleurone. 21 222+-independent, NEM-insensitive form of phosphatidate 12 phosphohydrolase (PAP2) (E.C. 3.1.3.4), leading to reduction of PA dephosphorylation and 13 increased PAK activity. Sequence analysis using Arabidopsis thaliana lipid phosphate 14 phosphatase (Lpp) sequences as queries identified two putative molecular homologues, 15 termed HvLPP1 and HvLPP2, encoding putative Lpps. The presence of well conserved 16 structural Lpp domains in these sequences, and the detection of proteins by 17 immunoblotting, suggest that both proteins are functional enzymes. Our results are 18 consistent with a role of DGPP as a regulator of ABA antagonist effect in GA signalling, 19 and provide evidence about regulation of PA level by a PAP2 during ABA response in 20 aleurone. 21 22Arabidopsis thaliana lipid phosphate 14 phosphatase (Lpp) sequences as queries identified two putative molecular homologues, 15 termed HvLPP1 and HvLPP2, encoding putative Lpps. The presence of well conserved 16 structural Lpp domains in these sequences, and the detection of proteins by 17 immunoblotting, suggest that both proteins are functional enzymes. Our results are 18 consistent with a role of DGPP as a regulator of ABA antagonist effect in GA signalling, 19 and provide evidence about regulation of PA level by a PAP2 during ABA response in 20 aleurone. 21 22HvLPP1 and HvLPP2, encoding putative Lpps. The presence of well conserved 16 structural Lpp domains in these sequences, and the detection of proteins by 17 immunoblotting, suggest that both proteins are functional enzymes. Our results are 18 consistent with a role of DGPP as a regulator of ABA antagonist effect in GA signalling, 19 and provide evidence about regulation of PA level by a PAP2 during ABA response in 20 aleurone. 21 22 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56