title: The Role of Phospholipase D and MAPK Signaling Cascades in the Adaption of Lichen Microalgae to Desiccation: Changes in Membrane Lipids and Phosphoproteome.
abstract: Classically, lichen phycobionts are described as poikilohydric organisms able to undergo desiccation due to the constitutive presence of molecular protection mechanisms. However, little is known about the induction of cellular responses in lichen phycobionts during drying. The analysis of the lipid composition of the desiccated lichen microalga Asterochloris erici revealed the unusual accumulation of highly polar lipids (oligogalactolipids and phosphatidylinositol), which prevents the fusion of membranes during stress, but also the active degradation of cone-shaped lipids (monogalactosyldiacylglycerol and phosphatidylethanolamine) to stabilize membranes in desiccated cells. The level of phosphatidic acid increased 7-fold during desiccation, implicating a possible role for phospholipase D (PLD) in the response to osmotic stress. Inhibition of PLD with 1-butanol markedly impaired the recovery of photosynthesis activity in A. erici upon desiccation and salt stress (2 M NaCl). These two hyperosmotic stresses caused the phosphorylation of c-Jun N-terminal kinase (JNK) and p38-like mitogen-activated protein kinase (MAPK) and the dephosphorylation of extracellular signal-regulated kinase (ERK). The incubation with 1-butanol reduced the phosphorylation of JNK-like proteins and increased the dephosphorylation of ERK-like proteins, which indicates an upstream control of MAPK cascades by PLD. The phosphoproteome showed that desiccation caused the phosphorylation of several proteins in A. erici, most of them involved in protein turnover. The results demonstrate that lichen phycobionts possess both constitutive and inducible protective mechanisms to acquire desiccation tolerance. Among others, these responses are controlled by the PLD pathway through the activation of MAPK cascades.
authors.affiliation: Departamento de Botánica & ICBIBE, Fac. C. Biológicas, Universitat de València, 46100 Burjassot, Spain Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, D-53115 Bonn, Germany francisco.gasulla@uv.es.
authors.forename: Francisco
authors.initials: F
authors.lastname: Gasulla
authors.affiliation: Departamento de Botánica & ICBIBE, Fac. C. Biológicas, Universitat de València, 46100 Burjassot, Spain.
authors.forename: Eva
authors.initials: E
authors.lastname: Barreno
authors.affiliation: Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain.
authors.forename: María L
authors.initials: ML
authors.lastname: Parages
authors.affiliation: Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Cámara
authors.affiliation: Departamento de Ecología, Facultad de Ciencias, Universidad de Málaga, 29071 Málaga, Spain.
authors.forename: Carlos
authors.initials: C
authors.lastname: Jiménez
authors.affiliation: Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, D-53115 Bonn, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Dörmann
authors.affiliation: Institute of Molecular Physiology and Biotechnology of Plants (IMBIO), University of Bonn, D-53115 Bonn, Germany.
authors.forename: Dorothea
authors.initials: D
authors.lastname: Bartels
mesh_terms: D000222:Adaptation, Physiological; D000460:Chlorophyta / Q000502:physiology; D003681:Dehydration; D008011:Lichens / Q000502:physiology*; D020935:MAP Kinase Signaling System; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism*; D058086:Microalgae / Q000502:physiology*; D009997:Osmotic Pressure; D010739:Phospholipase D / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation
chemical_list: D008563:Membrane Lipids; D010750:Phosphoproteins; D010739:Phospholipase D
keywords: Asterochloris erici; Desiccation tolerance; Lipid; MAPK; Phospholipase D; Phosphoproteome