Contact Information
Our research is focused on resolving how some vital processes in the plant cell membrane are regulated at the molecular level when plants are exposed to environmental stress.

Localization and expression of the 14-3-3 isoform omega at different developmental stages of an Arabidopsis flower as visualized by GUS staining.
Regulation of the plasma membrane proton pump (H+ATPase)
Plants have evolved a unique reliance on this pump, its function determines the function of all other transporters and channels in the membrane. Phosphorylation of the penultimate amino acid threonine in the autoinhibitory C terminus allows a 14-3-3 protein to bind which in turn results in activation of the proton pump. More than ten isoforms exist of both proton pumps and 14-3-3 proteins. Our goal is to understand the functional roles of the individual isoforms under different environmental regimes. We have indications that isoform specificity exists on tissue, organ, cell, and subcellular level as well as in the interaction between certain proton pumps and 14-3-3 isoforms.

Lipid-derived signalling
In response to a variety of external factors/cues phosphoinositides (PIs; membrane phospholipids) can give rise to several important intracellular signalling molecules that in turn affects Ca2+ levels and the following actions of the cell. We study regulation of PI cycle enzymes such as phosphatidylinositol phosphate kinase (PIPK), an enzyme that produces the signalling molecule PtdIns(4, 5)P2. PIPK knock-out mutants of the moss Physcomitrella patens revealed the importance of PIs in cell type development, rhizoid growth, and sporophyte production.
Ca2+ - binding proteins
The sensitivity and responses of the cell to various environmental stresses is often dependent on its ability to sequester and use Ca2+ from internal stores. We focus on the major Ca2+ -binding protein calreticulin, localised in the endoplasmic reticulum, with the aim to understand its detailed regulation and role in these processes as well as in protein folding. Arabidopsis has three isoforms and we have indications that they play complementary but also distinctly different roles, one of them seems to be involved in pathogenesis.
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Key publications

Alsterfjord M, Sehnke PC, Arkell A. Larsson H, Svennelid F, Rosenquist M, Ferl RJ, Sommarin M, Larsson C (2004). 14- 3-3 and H+-ATPase isoforms associated with the Arabidopsis leaf plasma membrane. Evidence for isoform specificity in the 14-3-3/H+-ATPase interaction in vivo. Plant Cell Physiol 45: 1202-10

Pical C, Westergren T, Dove SK, Larsson C, Sommarin M (1999). Salinity and hyperosmotic stress induce rapid increases in phosphatidylinositol 4, 5-bisphosphate, diacylglycerol pyrophosphate, and phosphatidylcholine in Arabidopsis thaliana cells. J Biol Chem 274: 38232-38240

Christensen A, Svensson K, Persson S, Michalak M, Jung J, Widell S, Sommarin M (2008). Functional characterization of Arabidopsis Calreticulin1a: a key alleviator of endoplasmic reticulum stress. Plant Cell Physiol 49: 912-924

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Publication list

  1. Saavedra L, Balbi V, Lerche J, Mikami K, Heilmann I, Sommarin M
    PIPKs are essential for rhizoid elongation and caulonemal cell development in the moss Physcomitrella patens
    The Plant Journal: 2011 67:635-647
  2. Mikami K, Saavedra L, Hiwatashi Y, Uji T, Hasebe M, Sommarin M
    A dibasic amino acid pair conserved in the activation loop directs plasma membrane localization and is necessary for activity of plant type I/II phosphatidylinositol phosphate kinase
    Plant Physiology: 2010 153:1004-1015
  3. Christensen A, Svensson K, Thelin L, Zhang WJ, Tintor N, Prins D, Funke N, Michalak M, Schulze-Lefert P, Saijo Y, Sommarin M, Widell S, Persson S
    Higher plant calreticulins have acquired specialized functions in Arabidopsis
    PLoS ONE 2010 5:e11342
  4. Saavedra L, Balbi V, Dove SK, Hiwatashi Y, Mikami K, Sommarin M
    Characterization of phosphatidylinositol phosphate kinases from the moss Physcomitrella patens: PpPIPK1 and PpPIPK2
    Plant and Cell Physiology: 2009 50(3):595-609
  5. Christensen A, Svensson K, Persson S, Jung, J., Michalak M, Widell S, Sommarin M
    Functional characterization of Arabidopsis calreticulin1a: A key alleviator of endoplasmic reticulum stress
    Plant and Cell Physiology: 2008 49:912-924
  6. Galindo FG, Elias L, Gekas V, Herppich WB, Smallwood M, Sommarin M, Worrall D, Sjoholm I
    On the induction of cold acclimation in carrots (Daucus carota L.) and its influence on storage performance
    Food Research International: 2005 38:29-36
  7. Persson S, Rosenquist M, Knoblach B, Far RK, Sommarin M, Michalak M
    Diversity of the protein disulfide isomerase family: identification of breast tumor induced Hag2 and Hag3 as novel members of the protein family
    Mol Phylogenet Evol: 2005 36:734-740
  8. Akesson A, Persson S, Love J, Boss WF, Widell S, Sommarin M
    Overexpression of the Ca2+-binding protein calreticulin in the endoplasmic reticulum improves growth of tobacco cell suspensions (Nicotiana tabacum) in high-Ca2+ medium
    Physiologia Plantarum: 2005 123:92-99
  9. Galindo FG, Vaughan D, Herppich W, Smallwood M, Sommarin M, Gekas V, Sjoholm I
    Influence of cold acclimation on the mechanical strength of carrot (Daucus carota L.) tissue
    European Journal of Horticultural Science: 2004 69:229-234
  10. Galindo FG, Brathen E, Knutsen SH, Sommarin M, Gekas V, Sjoholm I
    Changes in the carrot (Daucus carota L. cv. Nerac) cell wall during storage
    Food Research International: 2004 37:225-232
  11. Hunt L, Otterhag L, Lee JC, Lasheen T, Hunt J, Seki M, Shinozaki K, Sommarin M, Gilmour DJ, Pical C, Gray JE
    Gene-specific expression and calcium activation of Arabidopsis thaliana phospholipase C isoforms
    New Phytologist: 2004 162:643-654
  12. Alsterfjord M, Sehnke PC, Arkell A, Larsson H, Svennelid F, Rosenquist M, Ferl RJ, Sommarin M, Larsson C
    Plasma membrane H(+)-ATPase and 14-3-3 isoforms of Arabidopsis leaves: evidence for isoform specificity in the 14-3-3/H(+)-ATPase interaction
    Plant Cell Physiol: 2004 45:1202-1210
  13. Olsson P, Yilmaz JL, Sommarin M, Persson S, Bulow L
    Expression of bovine calmodulin in tobacco plants confers faster germination on saline media
    Plant Science: 2004 166:1595-1604
  14. Koch CLMB, Sommarin M, Persson BRR, Salford LG, Eberhardt JL
    Interaction between weak low frequency magnetic fields and cell membranes
    Bioelectromagnetics: 2003 24:395-402
  15. Persson S, Rosenquist M, Svensson K, Galv√£o R, Boss WF, Sommarin M
    Phylogenetic analyses and expression studies reveal two distinct groups of calreticulin isoforms in higher plants
    Plant Physiol: 2003 133:1385-1396
  16. Persson S, Rosenquist M, Sommarin M
    Identification of a novel calreticulin isoform (Crt2) in human and mouse
    Gene: 2002 297:151-158
  17. Gustavsson MH, Sommarin M
    Characterisation of a plasma membrane-associated phospholipase A(2) activity increased in response to cold acclimation
    Journal of Plant Physiology: 2002 159:1219-1227
  18. Sehnke PC, Rosenquist M, Alsterfjord M, DeLille J, Sommarin M, Larsson C, Ferl RJ
    Evolution and isoform specificity of plant 14-3-3 proteins
    Plant Mol Biol: 2002 50:1011-1018
  19. Westergren T, Dove SK, Sommarin M, Pical C
    AtPIP5K1, an Arabidopsis thaliana phosphatidylinositol phosphate kinase, synthesizes PtdIns(3,4)P-2 and PtdIns(4,5)P-2 in vitro and is inhibited by phosphorylation
    Biochemical Journal: 2001 359:583-589
  20. Otterhag L, Sommarin M, Pical C
    N-terminal EF-hand-like domain is required for phosphoinositide-specific phospholipase C activity in Arabidopsis thaliana
    FEBS Lett: 2001 497:165-170
  21. Wallstedt A, Sommarin M, Nilsson MC, Munson AD, Margolis HA
    The inhibition of ammonium uptake in excised birch (Betula pendula) roots by batatasin-III
    Physiologia Plantarum: 2001 113:368-376
  22. Rosenquist M, Alsterfjord M, Larsson C, Sommarin M
    Data mining the Arabidopsis genome reveals fifteen 14-3-3 genes. Expression is demonstrated for two out of five novel genes
    Plant Physiol: 2001 127:142-149
  23. Rosenquist M, Sehnke P, Ferl RJ, Sommarin M, Larsson C
    Evolution of the 14-3-3 protein family: does the large number of isoforms in multicellular organisms reflect functional specificity?
    J Mol Evol: 2000 51:446-458
  24. Villegas M, Sommarin M, Brodelius PE
    Effects of sodium orthovanadate on benzophenanthridine alkaloid formation and distribution in cell suspension cultures of Eschscholtzia californica
    Plant Physiology and Biochemistry: 2000 38:233-241
  25. Pical C, Westergren T, Dove SK, Larsson C, Sommarin M
    Salinity and hyperosmotic stress induce rapid increases in phosphatidylinositol 4,5-bisphosphate, diacylglycerol pyrophosphate, and phosphatidylcholine in Arabidopsis thaliana cells
    J Biol Chem: 1999 274:38232-38240
  26. Svennelid F, Olsson A, Piotrowski M, Rosenquist M, Ottman C, Larsson C, Oecking C, Sommarin M
    Phosphorylation of Thr-948 at the C terminus of the plasma membrane H+-ATPase creates a binding site for the regulatory 14-3-3 protein
    Plant Cell: 1999 11:2379-2391
  27. Westergren T, Ekblad L, Jergil B, Sommarin M
    Phosphatidylinositol 4-kinase associated with spinach plasma membranes. Isolation and characterization of two distinct forms
    Plant Physiology: 1999 121:507-516
  28. Puhakainen T, Pihakaski-Maunsbach K, Widell S, Sommarin M
    Cold acclimation enhances the activity of plasma membrane Ca2+ ATPase in winter rye leaves
    Plant Physiology and Biochemistry: 1999 37:231-239
  29. Olbe M, Sommarin M
    The spinach plasma membrane Ca2+ pump is a 120-kDa polypeptide regulated by calmodulin-binding to a terminal region
    Physiologia Plantarum: 1998 103:35-44
  30. Olsson A, Svennelid F, Ek B, Sommarin M, Larsson C
    A phosphothreonine residue at the C-terminal end of the plasma membrane H+-ATPase is protected by fusicoccin-induced 14-3-3 binding
    Plant Physiol: 1998 118:551-555
  31. Martensson B, Sommarin M, Widell S
    Peroxidase activity and ATP-dependent Ca2+ transport in subcellular fractions of embryogenic and non-embryogenic Daucus carota cell suspensions
    Plant Physiology and Biochemistry: 1998 36:515-524
  32. Olbe M, Widell S, Sommarin M
    Active calcium transporters in isolated membranes of wheat root cells
    Journal of Experimental Botany: 1997 48:1767-1777
  33. Jahn T, Fuglsang AT, Olsson A, Brüntrup IM, Collinge DB, Volkmann D, Sommarin M, Palmgren MG, Larsson C
    The 14-3-3 protein interacts directly with the C-terminal region of the plant plasma membrane H(+)-ATPase
    Plant Cell: 1997 9:1805-1814
  34. Olsson A, Jahn T, Bruntrup IM, Volkmann D, Sommarin M, Larsson C
    The fusicoccin-binding 14-3-3 protein interacts directly with the plant plasma membrane H+-ATPase
    Plant Physiology: 1997 114:1373-1373
  35. Johansson F, Olbe M, Sommarin M, Larsson C
    Brij-58, a Polyoxyethylene Acyl Ether, Creates Membrane-Vesicles of Uniform Sidedness - a New Tool to Obtain inside-out (Cytoplasmic Side-out) Plasma-Membrane Vesicles
    Plant Journal: 1995 7:165-173
  36. Olsson A, Johansson F, Sommarin M, Larsson C
    Multiple regulatory sites in the C-terminal autoinhibitory domain of the plasma membrane H+-ATPase
    Plant Journal: 1995 8:959-962
  37. Olbe M, Sommarin M, Gustafsson M, Lundborg T
    Effect of the Fungal Pathogen Bipolaris-Sorokiniana Toxin Prehelminthosporol on Barley Root Plasma-Membrane Vesicles
    Plant Pathology: 1995 44:625-635
  38. Sommarin M, Palmgren MG, Larsson C
    Regulation of the Plant Plasma-Membrane H+-Atpase Activity
    Biologicheskie Membrany: 1994 11:232-240
  39. Johansson F, Sommarin M, Larsson C
    Rapid Purification of the Plasma-Membrane H+-Atpase in Its Nonactivated Form Using Fplc
    Physiologia Plantarum: 1994 92:389-396
  40. Pical C, Fredlund KM, Petit PX, Sommarin M, Moller IM
    The Outer-Membrane of Plant-Mitochondria Contains a Calcium-Dependent Protein-Kinase and Multiple Phosphoproteins
    Febs Letters: 1993 336:347-351
  41. Johansson F, Sommarin M, Larsson C
    Fusicoccin Activates the Plasma Membrane H+-ATPase by a Mechanism Involving the C-Terminal Inhibitory Domain
    Plant Cell: 1993 5:321-327
  42. Lundberg GA, Sommarin M
    Diacylglycerol Kinase in Plasma-Membranes from Wheat
    Biochimica Et Biophysica Acta: 1992 1123:177-183
  43. Melin PM, Pical C, Jergil B, Sommarin M
    Polyphosphoinositide Phospholipase-C in Wheat Root Plasma-Membranes - Partial-Purification and Characterization
    Biochimica Et Biophysica Acta: 1992 1123:163-169
  44. Kuiper D, Sommarin M, Kylin A
    The Modulating Effects of Ph and Benzyladenine on the Ca2+Atpases and Mg2+-Atpases in the Plasmalemma of Wheat Root-Cells
    Physiologia Plantarum: 1992 84:367-373
  45. Pical C, Sandelius AS, Melin PM, Sommarin M
    Polyphosphoinositide Phospholipase-C in Plasma-Membranes of Wheat (Triticum-Aestivum L) - Orientation of Active-Site and Activation by Ca2+ and Mg2+
    Plant Physiology: 1992 100:1296-1303
  46. Palmgren MG, Sommarin M, Serrano R, Larsson C
    Identification of an Autoinhibitory Domain in the C-Terminal Region of the Plant Plasma-Membrane H+-Atpase
    Journal of Biological Chemistry: 1991 266:20470-20475
  47. Kuiper D, Sommarin M, Kylin A
    The Effects of Mineral-Nutrition and Benzyladenine on the Plasmalemma Atpase Activity from Roots of Wheat and Plantago-Major Ssp-Pleiosperma
    Physiologia Plantarum: 1991 81:169-174
  48. Olbe M, Sommarin M
    Atp-Dependent Ca2+ Transport in Wheat Root Plasma-Membrane Vesicles
    Physiologia Plantarum: 1991 83:535-543
  49. Widell S, Sommarin M
    Purification of Endoplasmic-Reticulum from Wheat Roots and Shoots (Triticum-Aestivum) - Comparison of Their Blue Light-Sensitive Redox Components with Those of Highly Purified Plasma-Membrane
    Physiologia Plantarum: 1991 82:9-18
  50. Palmgren MG, Sommarin M, Ulvskov P, Larsson C
    Effect of Detergents on the H+-Atpase Activity of inside-out and Right-Side-out Plant Plasma-Membrane Vesicles
    Biochimica Et Biophysica Acta: 1990 1021:133-140
  51. Sommarin M, Petit PX, Moller IM
    Endogenous Protein-Phosphorylation in Purified Plant-Mitochondria
    Biochimica Et Biophysica Acta: 1990 1052:195-203
  52. Palmgren MG, Larsson C, Sommarin M
    Proteolytic Activation of the Plant Plasma-Membrane H+-Atpase by Removal of a Terminal Segment
    Journal of Biological Chemistry: 1990 265:13423-13426
  53. Petit PX, Sommarin M, Pical C, Moller IM
    Modulation of Endogenous Protein-Phosphorylation in Plant-Mitochondria by Respiratory Substrates
    Physiologia Plantarum: 1990 80:493-499
  54. Palmgren MG, Askerlund P, Fredrikson K, Widell S, Sommarin M, Larsson C
    Sealed inside-out and Right-Side-out Plasma-Membrane Vesicles - Optimal Conditions for Formation and Separation
    Plant Physiology: 1990 92:871-880
  55. Palmgren MG, Sommarin M
    Lysophosphatidylcholine Stimulates Atp Dependent Proton Accumulation in Isolated Oat Root Plasma-Membrane Vesicles
    Plant Physiology: 1989 90:1009-1014
  56. Sommarin M, Sandelius AS
    Phosphatidylinositol and Phosphatidylinositolphosphate Kinases in Plant Plasma-Membranes
    Biochimica Et Biophysica Acta: 1988 958:268-278
  57. Larsson C, Widell S, Sommarin M
    Inside-out Plant Plasma-Membrane Vesicles of High-Purity Obtained by Aqueous 2-Phase Partitioning
    Febs Letters: 1988 229:289-292
  58. Palmgren MG, Sommarin M, Jorgensen PL
    Substrate Stabilization of Lysophosphatidylcholine- Solubilized Plasma-Membrane H+-Atpase from Oat Roots
    Physiologia Plantarum: 1988 74:20-25
  59. Palmgren MG, Sommarin M, Ulvskov P, Jorgensen PL
    Modulation of Plasma-Membrane H+-Atpase from Oat Roots by Lysophosphatidylcholine, Free Fatty-Acids and Phospholipase-A2
    Physiologia Plantarum: 1988 74:11-19
  60. Melin PM, Sommarin M, Sandelius AS, Jergil B
    Identification of Ca-2+-Stimulated Polyphosphoinositide Phospholipase-C in Isolated Plant Plasma-Membranes
    Febs Letters: 1987 223:87-91
  61. Memon AR, Sommarin M, Kylin A
    Plasmalemma from the Roots of Cucumber - Isolation by 2-Phase Partitioning and Characterization
    Physiologia Plantarum: 1987 69:237-243
  62. Gierow P, Sommarin M, Larsson C, Jergil B
    Fractionation of Rat-Liver Plasma-Membrane Regions by 2-Phase Partitioning
    Biochemical Journal: 1986 235:685-691
  63. Sandelius AS, Sommarin M
    Phosphorylation of Phosphatidylinositols in Isolated Plant Membranes
    Febs Letters: 1986 201:282-286