Lipid Phosphate Phosphatases in Arabidopsis: REGULATION OF THE AtLPP1 GENE IN RESPONSE TO STRESS

Olivier Pierrugues,Catherine Brutesco,June Oshiro,Manolo Gouy,Yves Deveaux,George M Carman,Pierre Thuriaux,Michael Kazmaier

doi:10.1074/jbc.m009726200

Abstract

An Arabidopsis thaliana gene (AtLPP1) was isolated on the basis that it was transiently induced by ionizing radiation. The putative AtLPP1 gene product showed homology to the yeast and mammalian lipid phosphate phosphatase enzymes and possessed a phosphatase signature sequence motif. Heterologous expression and biochemical characterization of the AtLPP1 gene in yeast showed that it encoded an enzyme (AtLpp1p) that exhibited both diacylglycerol pyrophosphate phosphatase and phosphatidate phosphatase activities. Kinetic analysis indicated that diacylglycerol pyrophosphate was the preferred substrate for AtLpp1p in vitro. A second Arabidopsis gene (AtLPP2) was identified based on sequence homology to AtLPP1 that was also heterologously expressed in yeast. The AtLpp2p enzyme also utilized diacylglycerol pyrophosphate and phosphatidate but with no preference for either substrate. The AtLpp1p and AtLpp2p enzymes showed differences in their apparent affinities for diacylglycerol pyrophosphate and phosphatidate as well as other enzymological properties. Northern blot analyses showed that the AtLPP1 gene was preferentially expressed in leaves and roots, whereas the AtLPP2 gene was expressed in all tissues examined. AtLPP1, but not AtLPP2, was regulated in response to various stress conditions. The AtLPP1 gene was transiently induced by genotoxic stress (gamma ray or UV-B) and elicitor treatments with mastoparan and harpin. The regulation of the AtLPP1 gene in response to stress was consistent with the hypothesis that its encoded lipid phosphate phosphatase enzyme may attenuate the signaling functions of phosphatidate and/or diacylglycerol pyrophosphate that form in response to stress in plants.

Highlights

An Arabidopsis thaliana gene (AtLPP1) was isolated on the basis that it was transiently induced by ionizing radiation
The 8-fold elevation of hybridizing mRNA levels in response to radiation stress was restricted in time to 30 min Regulation of the Arabidopsis AtLPP1 Gene in Response to Stress immediately following the radiation injury
Several lipid phosphate phosphatase enzymes have been described from S. cerevisiae and mammalian cells [7, 9]

Summary

Introduction

An Arabidopsis thaliana gene (AtLPP1) was isolated on the basis that it was transiently induced by ionizing radiation. Heterologous expression and biochemical characterization of the AtLPP1 gene in yeast showed that it encoded an enzyme (AtLpp1p) that exhibited both diacylglycerol pyrophosphate phosphatase and phosphatidate phosphatase activities. The regulation of the AtLPP1 gene in response to stress was consistent with the hypothesis that its encoded lipid phosphate phosphatase enzyme may attenuate the signaling functions of phosphatidate and/or diacylglycerol pyrophosphate that form in response to stress in plants. Recent studies with a variety of plant systems have shown that PA and DGPP transiently accumulate after elicitor treatment or in response to stress (5, 10 –12) These observations have suggested that these phospholipid molecules play a role in plant signal transduction [10, 11]. Plant lipid phosphate phosphatase enzymes able to remove elevated levels of PA and DGPP during the early phase of stress response have not yet been described

Methods

Results

Conclusion