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First published online February 11, 2009; 10.1104/pp.108.131714 Plant Physiology 149:1739-1750 (2009) © 2009 American Society of Plant Biologists OPEN ACCESS ARTICLE
Exploring the Mechanism of Physcomitrella patens Desiccation Tolerance through a Proteomic Strategy1,[W],[OA]College of Life Sciences, Capital Normal University, Beijing 100048, China (X.Q.W., W.Z.L., Y.H., T.Y.K., Y.K.H.); Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China (X.Q.W., H.C., T.Y.K., S.H.S.); Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824(P.F.Y.); Department of Plant Sciences, University of Cambridge, Cambridge CB2 3EA, United Kingdom (Z.L.); and Department of Biology, Duke University, Durham, North Carolina 27708 (Z.M.P.)
The moss Physcomitrella patens has been shown to tolerate abiotic stresses, including salinity, cold, and desiccation. To better understand this plant's mechanism of desiccation tolerance, we have applied cellular and proteomic analyses. Gametophores were desiccated over 1 month to 10% of their original fresh weight. We report that during the course of dehydration, several related processes are set in motion: plasmolysis, chloroplast remodeling, and microtubule depolymerization. Despite the severe desiccation, the membrane system maintains integrity. Through two-dimensional gel electrophoresis and image analysis, we identified 71 proteins as desiccation responsive. Following identification and functional categorization, we found that a majority of the desiccation-responsive proteins were involved in metabolism, cytoskeleton, defense, and signaling. Degradation of cytoskeletal proteins might result in cytoskeletal disassembly and consequent changes in the cell structure. Late embryogenesis abundant proteins and reactive oxygen species-scavenging enzymes are both prominently induced, and they might help to diminish the damage brought by desiccation.
Water is a key component of living organisms and one of the critical environmental factors that controls the distribution of plants on the earth. With increasing urbanization and human progress, water deficiency looms as a widespread and worsening agricultural problem. In such a scenario, the ability of plants to tolerate water deficit has important economic ramifications.
Since the first plant grew on land, plants have had to confront different kinds of extreme environmental stresses. Desiccation, defined as the complete loss of "free" water from an organism (Gaff, 1971
Desiccation tolerance is a complex phenomenon that is just beginning to be understood. Many scientists believe that a thorough understanding of desiccation tolerance mechanisms will facilitate the creation of water-tolerant crop species (Bartels and Sunkar, 2005
More recently, genomic-level studies have been initiated. Most of these studies have made gene expression profiles (Oliver et al., 2004
The moss Physcomitrella patens has been used as a model system in plant science for years because of the several advantages it offers (Frank et al., 2005
P. patens Is a Desiccation-Tolerant Plant Four-week-old P. patens gametophores were subjected to slow dehydration by drying in a desiccator until there was a 90% loss in their fresh weight. Usually, it takes 1 month to obtain desiccated P. patens gametophores. As a consequence of the severe water loss involved, we define this treatment as desiccation. Besides the shrinking of the P. patens gametophores, the color changed to dark green during desiccation treatment (Fig. 1, A and B ). During the treatment, chlorophyll content declined slightly, particularly as water loss became more extreme (Fig. 2 ). Interestingly, desiccation did not result in the death of the P. patens gametophores. Following the desiccation treatment, the P. patens gametophores were rehydrated by floating in distilled water for 2 h and subsequently cultivated in standard growth conditions. This rehydration promoted the recovery of plants that thereafter exhibited vigorous growth and development, all but indistinguishable from that of untreated plants. In neither morphology nor fresh weight (data not shown) could we detect significant differences between control plants and those subjected to desiccation and rehydration (Fig. 1, C and D). Based on these results, we conclude that P. patens is desiccation tolerant.
Cellular Structure in Desiccated P. patens
As a desiccation-tolerant plant, P. patens must be able to limit damage to a repairable level and to maintain the integrity of cellular structures during desiccation. In the desiccated state, the central large vacuoles were broken into many small vesicles and the cytoplasm appeared far denser than it did prior to treatment (Fig. 3, A and B
). In spite of the dramatic shrinkage of the cell, the plasma membrane seemed to maintain its integrity, as judged from complete profiles encircling the protoplast and by clear differences in density between the cytoplasm and periplasm. During desiccation, chloroplasts appeared more spherical compared with their usual ellipsoidal shape (Fig. 3, A and B), consistent with morphologies reported previously to occur in vascular plants subjected to drought and salt stresses (Abdelkader et al., 2007
Proteome Profile of P. patens during Desiccation To gain further understanding of the molecular mechanisms that contribute to the survival of gametophores of P. patens, we extracted total proteins from control and desiccated gametophores and separated them using two-dimensional gel electrophoresis (2-DE). Representative 2-DE images were established for both the control and treated samples in a pI range of pH 4 to 7 and a molecular mass range of 10 to 100 kD (Fig. 4 ). There were obvious differences between the gels of control and desiccated plants, which indicated that desiccation dramatically changed the profile of expressed proteins of the gametophores.
To analyze the changes in the proteome profile, we compared gels of each sample, digitized after staining with Coomassie Brilliant Blue as described in "Materials and Methods." Data from three biological replicates were collected, and only those spots that were detected on all three replicate gels were used. Based on this criterion, more than 1,300 protein spots could be detected for each sample. Statistical analysis of the data from all replicates enabled us to identity 71 protein spots that were significantly altered in response to the desiccation. Among them, 25 spots represented down-regulated proteins (spots D1–D25; Fig. 4), 33 spots represented up-regulated proteins (spots U26–U58; Fig. 4), and 13 spots represented de novo-induced proteins (spots I59–I71; Fig. 4). Quantitative data confirmed that the abundance of these proteins was altered significantly (Fig. 5 ).
The desiccation response is a complicated physiological process in which many biochemical processes might be initiated or inhibited. So it is reasonable to expect changes in the abundance of many proteins; however, only 71 of 1,300 spots changed intensity by more than 2-fold. This surprising stability of the desiccated proteome suggests that those 71 proteins that did change are worthy of further attention for elucidating the mechanism of desiccation tolerance.
To categorically identify the nature of proteins involved in desiccation tolerance, we used a liquid chromatography-tandem mass spectrometry (LC-MS/MS) approach. All 71 differentially displayed protein spots were excised from preparative 2-D gels, digested with trypsin, and analyzed through LC-MS/MS. We searched the amino acid sequences against the databases using the SEQEST software as described before (Wang et al., 2008
Changes of Metabolic Proteins Twenty-five proteins categorized within the metabolism group were altered dramatically in response to desiccation treatment (Table I; Fig. 6). Among these proteins, eight were down-regulated and 17 were either induced or up-regulated. Proteins of this category are involved in basic metabolic processes such as photosynthesis, sugar catabolism, and amino acid metabolism. Generally, the proteins involved in anabolism are down-regulated and those involved in catabolism are up-regulated (or induced) by desiccation (Table I). Photosynthesis is one major characteristic metabolic process of green plants. Under desiccation conditions, both the large (spot D14) and small (spots D23 and D25) subunits of Rubisco, which is a major photosynthetic enzyme, decreased steeply in abundance (Fig. 5). Desiccation also down-regulated chloroplast ATP synthases (spots D3 and D19). Nonetheless, the light-harvesting chlorophyll a/b-binding protein 2 (spots I59 and I60) and a major chlorophyll-binding protein (spot I61) were induced. Interestingly, the observed molecular masses of these three chlorophyll-binding proteins were higher than their theoretical masses by about 44 kD. The reason for this increase is not clear but might result from an unusual posttranslational modification.
Several proteins that are involved in sugar catabolism were found to be up-regulated during desiccation. These proteins include In addition to the above-mentioned proteins, some proteins involved in the metabolism of fatty acids, amino acids, and nucleotides also changed in abundance in response to the desiccation treatment. These proteins include enoyl-CoA hydratase (spot I69), 3-isopropylmalate dehydrogenase (spot D5), S-adenosylmethionine synthetase (spot D6), ketol acid reductoisomerase (spot U27), aminoacylase (spot U40), subtilisin-like proteases (spot I63), and phosphoribosyl diphosphate synthase (spots I65 and I71; Table I; Figs. 4 and 5).
Several cytoskeletal proteins were identified as desiccation responsive. Except for ftsZ1 (spot U46), the changed cytoskeletal proteins were all down-regulated by desiccation. These were β-tubulin (spot D1),
Proteins Involved in Defense and Signaling
Upon desiccation, many proteins related to defense and signaling underwent large changes in abundance. Interestingly, all of these changed defense or signaling proteins were up-regulated (Table I; Fig. 5). These might be instrumental in protecting the cells from incurring damage during the desiccation treatment. We identified three signaling proteins: calcium-dependent protein kinase-like protein (spot U28), Ser/Thr-specific protein kinase-like protein (spot U32), and IAA/AUX protein (spot U48). The defense proteins included heat shock proteins (HSPs; spots U29, U35, U36, U37, and U38; mainly HSP70), luminal binding protein (spot U55), the endoplasmic reticulum molecular chaperone, which also belongs to the HSP70 family (Rothman, 1989
The majority of the vegetative desiccation-tolerant plants belong to the algae, lichens, and bryophytes, all of which belong evolutionarily to early-arising clades within the plant kingdom (Oliver et al., 2000a  ). A recent survey has shown that about 158 species of mosses are vegetative desiccation tolerant (Wood, 2007). In this study, we show that the model moss P. patens is also desiccation tolerant. It recovers following a severe desiccation treatment. The ultrastructural and proteomic studies can help to reveal the strategy applied by this moss species to survive desiccation.
Desiccation is a phenomenon of severe water loss. To be desiccation tolerant, a plant must meet three criteria: (1) constrain the damage to a repairable level; (2) maintain its cellular integrity under the desiccation conditions; and (3) immediately mobilize the repair mechanisms upon hydration (Bewley, 1979
Additionally, we found that desiccation resulted in the up-regulation of rhamnose biosynthetic enzyme 1 (spot U43). This enzyme catalyzes the synthesis of rhamnose, which is a prominent component of cell wall pectin. In angiosperms, pectins have been linked to communication between cell wall and cytoplasm, particularly during periods of stress (Humphrey et al., 2007
Based on the changes in their photosynthesis apparatus, the vegetative desiccation-tolerant plants can be divided into homoiochlorophyllous and poikilochlorophyllous types (Tuba et al., 1998
An important player in the reorganization of the photosynthetic apparatus might be FtsZ (spot U46; Kiessling et al., 2000
The cytoskeleton forms a dynamic framework that maintains cell shape and organelle motility (Smith, 2003
Alpert and Oliver (2002)
Respiration was probably affected to a lesser extent than was photosynthesis. Tuba et al. (1996)
As we described above, all of the defense and signaling proteins identified in our study were up-regulated by desiccation. This suggests that these proteins play important roles in ensuring the survival of desiccated P. patens. The late embryogenesis abundant (LEA) proteins were first found in plant seeds (Dure et al., 1981
HSPs maintain partner proteins in a folding-competent, folded, or unfolded state to minimize aggregation of nonnative proteins or to target nonnative or aggregated proteins for degradation and removal from the cell (Bukau and Horwich, 1998
In addition to the above-mentioned proteins, we also found that certain antioxidative proteins were up-regulated (or induced; Table I). Mechanisms for scavenging reactive oxygen play major roles and act in several organelles, particularly in extreme environments, including dehydration (Smirnoff, 1998
As early land-growing plants, bryophytes like P. patens pioneered responses to numerous extreme stresses during their life cycle. Furthermore, most bryophyte organs, being single cell sheets or filaments, exacerbate the risks of incurring stress-related damage. Nevertheless, P. patens survives robustly under various environmental stresses, including high salt, low temperature, and desiccation. Here, we show that the proteome changes during desiccation are few and in selected functional categories, as expected from a well-choreographed response. The challenge now is to discover how each of these groups actually moves the plant toward its goal of survival. We expect that careful proteomic analysis can continue to play an important role in these discoveries.
Plant Materials and Growth Conditions
Physcomitrella patens ecotype ‘Gransden 2004’ was grown in modified BCD medium (1 mM MgSO4, 10 mM KNO3, 45 mM FeSO4, 1.8 mM KH2PO4, pH 6.5) containing 0.5% (w/v) Glc and 0.75% (w/v) agar (Ashton et al., 1979
To determine water content, gametophores were weighted at harvest and then dried in an oven at 105°C for 3 d and weighed again. Water content was calculated as the difference between fresh and dry weights divided by fresh weight and expressed as a percentage. To determine chlorophyll content, freshly harvested samples were extracted in a 1:1 mixture of acetone and ethanol, as described by Chen (1984)
For transmission electron microscopy, fresh tissues were taken and immediately immersed in 2.5% glutaraldehyde fixative in phosphate buffer (0.1 M, pH 7.0) for 10 min and then in fresh fixative at 4°C for 3 h in darkness. Specimens were subsequently buffer washed, postfixed in 1% OsO4 solution at 4°C for 5 h, dehydrated in a graded ethanol series followed by propylene oxide, and embedded in LX 122 Epon. Sections were poststained for 5 min in saturated aqueous uranyl nitrate and for 5 min in lead citrate. Specimens were examined with a Philips EM-420 electron microscope.
The following antibodies were used: a monoclonal anti-tubulin antibody (Sigma; DM 1A T9026) and goat anti-mouse IgG-fluorescein isothiocyanate (Sigma; IF0030). Gametophores were fixed for 1 h in PME buffer (50 mM PIPES, 5 mM EGTA, and 2 mM MgSO4, pH 6.5) containing 4% paraformaldehyde. The gametophores were cut into fragments and washed with PME three times for 10 min each, then treated with 1% Triton X-100 for 30 min and washed with PME three times for 10 min. Blocking was performed in phosphate-buffered saline (PBS) with 1% bovine serum albumin overnight, and then the samples were stained with monoclonal anti-tubulin antibody at 4°C overnight. Washing three times with PBS was followed by incubations with the secondary antibody for 2 h at room temperature in darkness, followed by three 10-min washes with PBS. The fragments were then mounted in Elvanol under a coverslip. Images were acquired with a Leica SP2 confocal microscope using a 60x water objective. All images presented were assembled using the Photoshop 7.0 software package (Adobe Systems).
Proteins were extracted using a phenol extraction procedure. Plant tissue (2 g) was ground to fine powder in liquid nitrogen and homogenized on ice for 30 min with 6 mL of ice-cold extraction buffer (250 mM Suc, 20 mM Tris-HCl, pH 7.5, 10 mM EDTA, 1 mM phenylmethylsulfonyl fluoride, and 1 mM 1,4-dithiothreitol [DTT]). Then an equal volume of ice-cold Tris-HCl (pH 7.5)-saturated phenol was added, and the mixture was rehomogenized for 30 min on ice. After centrifugation (20 min, 15,000g, 4°C), the phenol phase was collected and reextracted two times with extraction buffer as described above. Proteins were precipitated from the final phenol phase with 3 volumes of 100 mM ammonium acetate in methanol overnight at –20°C. The pellets were rinsed three times with ice-cold acetone containing 13 mM DTT and then lyophilized. The resulting pellets were dissolved in a rehydration buffer (7 M urea, 2 M thiourea, 4% [w/v] CHAPS, 0.5% [v/v] immobilized pH gradient buffer, and 1% [w/v] DTT) at room temperature. 2-DE was carried out as follows: dry immobilized pH gradient strips (13 cm long, pH 4–7 linear) were rehydrated for 12 h in 250 µL of rehydration buffer containing 800-µg protein samples. Isoelectric focusing was conducted at 20°C with an Ettan IPGphor system (GE Healthcare BIO-Science). Focusing was performed in four steps: 300 V for 1 h, 600 V for 1 h, 1,000 V for 1 h, and 8,000 V for 6 h. Focused strips were then equilibrated by first incubating them in an equilibration solution (6 M urea, 30% [v/v] glycerol, 2% [w/v] SDS, 50 mM Tris-HCl, pH 8.8, and 1% [w/v] DTT) for 15 min, followed by incubation in 4% (w/v) iodoacetamide in the same equilibration solution for 15 min. For the second dimension, the proteins were separated on 15% SDS-polyacrylamide gels. Protein spots were stained with Coomassie Brilliant Blue R-250.
The 2-DE gels were scanned at a resolution of 600 dots per inch with a UMAX Power Look 2100XL scanner (Maximum Tech). The transparency mode was used to obtain a grayscale image. The image analysis was performed with an ImageMaster 2D Platinum version 5.0 (GE Healthcare BIO-Science). The optimized parameters were as follows: saliency, 2.0; partial threshold, 4; and minimum area, 50. We quantified spots by determining the ratio of the volume of a single spot to the whole set of spots. Only those with that changed by more than 2-fold in each of the three replicates were used for further analysis.
Protein spots were manually excised from the gel, and in-gel digestion by trypsin was performed according to Shen et al. (2003)
LC was performed on a surveyor LC system (Thermo Finnigan). The C18 column was obtained from Column Technology. Mobile phase A was 0.1% formic acid in water, and mobile phase B was 0.1% formic acid in acetonitrile. The tryptic peptide mixtures were eluted using a gradient of 2% to 98% B over 180 min. The MS/MS was performed on a LTQ linear ion trap mass spectrometer (Thermo Finnigan) equipped with an electrospray interface and operated in positive ion mode. The capillary temperature was set to 170°C, and the spray voltage was at 3.4 kV. The acquired MS/MS spectra were compared against the National Center for Biotechnology Information Arabidopsis and P. patens protein database using the TurboSEQUEST program in the BioWorks 3.1 software suite (Thermo Finnigan). An accepted SEQUEST result had to have a
The following materials are available in the online version of this article.
We thank Professor Tobias I. Baskin (Biology Department, University of Massachusetts-Amherst) for improving the manuscript. Received October 25, 2008; accepted January 30, 2009; published February 11, 2009.
1 This work was supported by the Chinese 863 Project (grant no. 2007AA021405), the Beijing National Science Key Foundation (grant nos. KZ20061002817 and 5021001), and the Funding Project for Academic Human Resources Development in Institutions of Higher Learning under the Jurisdiction of Beijing Municipality to Y.K.H. 
2 These authors contributed equally to the article. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Yi Kun He (yhe{at}mail.cnu.edu.cn).
[W] The online version of this article contains Web-only data.
[OA] Open Access articles can be viewed online without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.108.131714 * Corresponding author; e-mail yhe{at}mail.cnu.edu.cn.
Abdelkader AF, Aronsson H, Solymosi K, Boddi B, Sundqvist C (2007) High salt stress induces swollen prothylakoids in dark-grown wheat and alters both prolamellar body transformation and reformation after irradiation. J Exp Bot 58: 2553–2564 Allagulova Ch R, Gimalov FR, Shakirova FM, Vakhitov VA (2003) The plant dehydrins: structure and putative functions. Biochemistry (Mosc) 68: 945–951[CrossRef][Medline] Alpert P, Oliver MJ (2002) Drying without dying. In M Black, HW Pritchard, eds, Desiccation and Survival in Plants. CABI Publishing, Wallingford, UK, pp 3–43 Apel K, Hirt H (2004) Reactive oxygen species: metabolism, oxidative stress, and signal transduction. Annu Rev Plant Biol 55: 373–399[CrossRef][Medline] Arnon DI (1949) Copper enzymes in isolated chloroplasts: polyphenoloxidase in Beta vulgaris. Plant Physiol 24: 1–15 Ashton N, Cove D, Featherstone DR (1979) The isolation and physiological analysis of mutants of the moss, Physcomitrella patens, which over-produce gametophores. Planta 144: 437–442[CrossRef][Web of Science] Balla G, Jacob HS, Balla J, Rosenberg M, Nath K, Apple F, Eaton JW, Vercellotti GM (1992) Ferritin: a cytoprotective antioxidant strategem of endothelium. J Biol Chem 267: 18148–18153 Barhoumi Z, Djebali W, Chaibi W, Abdelly C, Smaoui A (2007) Salt impact on photosynthesis and leaf ultrastructure of Aeluropus littoralis. J Plant Res 120: 529–537[CrossRef][Web of Science][Medline] Bartels D, Sunkar R (2005) Drought and salt tolerance in plants. Crit Rev Plant Sci 24: 1–36[CrossRef] Bevan M, Bancroft I, Bent E, Love K, Goodman H, Dean C, Bergkamp R, Dirkse W, Van Staveren M, Stiekema W, et al (1998) Analysis of 1.9 Mb of contiguous sequence from chromosome 4 of Arabidopsis thaliana. Nature 391: 485–488[CrossRef][Medline] Bewley JD (1979) Physiological aspects of desiccation tolerance. Annu Rev Plant Physiol 30: 195–238[Web of Science] Bewley JD, Oliver MJ (1992) Desiccation tolerance in vegetative plant tissues and seeds: protein synthesis in relation to desiccation and a potential role for protection and repair mechanisms. In CB Osmond, G Somero, eds, Water and Life: A Comparative Analysis of Water Relationships at the Organismic, Cellular and Molecular Levels. Springer-Verlag, Berlin, pp 141–160 Bohnert HJ, Gong Q, Li P, Ma S (2006) Unraveling abiotic stress tolerance mechanisms: getting genomics going. Curr Opin Plant Biol 9: 180–188[CrossRef][Web of Science][Medline] Bukau B, Horwich AL (1998) The Hsp70 and Hsp60 chaperone machines. Cell 92: 351–366[CrossRef][Web of Science][Medline] Chen FM (1984) Determining the chlorophyll contents of plant leaves by acetone/ethanol mixture assay. For Sci Commun 2: 4–8 Close TJ (1996) Dehydrins: emergence of a biochemical role of a family of plant dehydration proteins. Physiol Plant 97: 795–803[CrossRef] Close TJ (1997) Dehydrins: a commonality in the response of plants to dehydration and low temperatures. Physiol Plant 100: 291–296[CrossRef] de Castro RD, Zheng X, Bergervoet JHW, De Vos CHR, Bino RJ (1995) β-Tubulin accumulation and DNA replication in imbibing tomato seeds. Plant Physiol 109: 499–504[Abstract] Dure L III, Greenway SC, Galau GA (1981) Developmental biochemistry of cottonseed embryogenesis and germination: changing messenger ribonucleic acid populations as shown by in vitro and in vivo protein synthesis. Biochemistry 20: 4162–4168[CrossRef][Web of Science][Medline] El-Kafafi el-S, Karamoko M, Pignot-Paintrand I, Grunwald D, Mandaron P, Lerbs-Mache S, Falconet D (2008) Developmentally regulated association of plastid division protein FtsZ1 with thylakoid membranes in Arabidopsis thaliana. Biochem J 409: 87–94[CrossRef][Web of Science][Medline] Farrant JM (2000) A comparison of mechanisms of desiccation tolerance among three angiosperm resurrection plant species. Plant Ecol 151: 29–39[CrossRef] Frank W, Decker EL, Reski R (2005) Molecular tools to study Physcomitrella patens. Plant Biol 7: 220–227[CrossRef][Medline] Gaff DF (1971) Desiccation-tolerant flowering plants in southern Africa. Science 174: 1033–1034 Harrison PM, Arosio P (1996) The ferritins: molecular properties, iron storage function and cellular regulation. Biochim Biophys Acta 1275: 161–203[Medline] Hoekstra FA, Golovina EA, Buitink J (2001) Mechanisms of plant desiccation tolerance. Trends Plant Sci 6: 431–438[CrossRef][Web of Science][Medline] Humphrey TV, Bonetta DT, Goring DR (2007) Sentinels at the wall: cell wall receptors and sensors. New Phytol 176: 7–21[CrossRef][Web of Science][Medline] Hundertmark M, Hincha DK (2008) LEA (Late Embryogenesis Abundant) proteins and their encoding genes in Arabidopsis thaliana. BMC Genomics 9: 118–139[CrossRef][Medline] Iturriaga G, Cushman MAF, Cushman JC (2006) An EST catalogue from the resurrection plant Selaginella moellendorfii reveals abiotic stress-adaptive genes. Plant Sci 170: 1173–1184[CrossRef][Web of Science] Juckett MB, Balla J, Balla G, Jessurun J, Jacob HS, Vercellotti GM (1995) Ferritin protects endothelial cells from oxidized low density lipoprotein in vitro. Am J Pathol 147: 782–789[Abstract] Kiessling J, Kruse S, Rensing SA, Harter K, Decker EL, Reski R (2000) Visualization of a cytoskeleton-like FtsZ network in chloroplasts. J Cell Biol 151: 945–950 Kiessling J, Martin A, Gremillon L, Rensing SA, Nick P, Sarnighausen E, Decker EL, Reski R (2004) Dual targeting of plastid division protein FtsZ to chloroplasts and the cytoplasm. EMBO Rep 5: 889–894[CrossRef][Web of Science][Medline] Komis G, Galatis B, Quader H, Galanopoulou D, Apostolakos P (2008) Phospholipase C signaling involvement in macrotubule assembly and activation of the mechanism regulating protoplast volume in plasmolyzed root cells of Triticum turgidum. New Phytol 178: 267–282[CrossRef][Web of Science][Medline] McAndrew RS, Froehlich JE, Vitha S, Stokes KD, Osteryoung KW (2001) Colocalization of plastid division proteins in the chloroplast stromal compartment establishes a new functional relationship between FtsZ1 and FtsZ2 in higher plants. Plant Physiol 127: 1656–1666 Mikkelsen R, Baunsgaard L, Blennow A (2004) Functional characterization of alpha-glucan, water dikinase, the starch phosphorylating enzyme. Biochem J 377: 525–532[CrossRef][Web of Science][Medline] Minami A, Nagao M, Ikegami K, Koshiba T, Arakawa K, Fujikawa S, Takezawa D (2005) Cold acclimation in bryophytes: low-temperature-induced freezing tolerance in Physcomitrella patens is associated with increases in expression levels of stress-related genes but not with increase in level of endogenous abscisic acid. Planta 220: 414–423[CrossRef][Web of Science][Medline] Oliver MJ (1991) Influence of protoplasmic water loss on the control of protein synthesis in the desiccation-tolerant moss Tortula ruralis: ramifications for a repair-based mechanism of desiccation tolerance. Plant Physiol 97: 1501–1511 Oliver ML, Bewley JD (1997) Desiccation-tolerance of plant tissues: a mechanistic overview. Hortic Rev (Am Soc Hortic Sci) 18: 171–213 Oliver MJ, Dowd SE, Zaragoza J, Mauget SA, Payton PR (2004) The rehydration transcriptome of the desiccation-tolerant bryophyte Tortula ruralis: transcript classification and analysis. BMC Genomics 89: 1–19 Oliver MJ, Tuba Z, Mishler BD (2000a) The evolution of vegetative desiccation tolerance in land plants. Plant Ecol 151: 85–100[CrossRef] Oliver MJ, Velten J, Mishler BD (2005) Desiccation tolerance in bryophytes: a reflection of the primitive strategy for plant survival in dehydrating habitats? Integr Comp Biol 45: 788–799 Oliver MJ, Velten J, Wood AJ (2000b) Bryophytes as experimental models for the study of environmental stress tolerance: Tortula ruralis and desiccation-tolerance in mosses. Plant Ecol 151: 73–84[CrossRef] Piatkowski D, Schneider K, Salamini F, Bartels D (1990) Characterization of five abscisic acid-responsive cDNA clones isolated from the desiccation-tolerant plant Craterostigma plantagineum and their relationship to other water-stress genes. Plant Physiol 94: 1682–1688 Porembski S, Barthlott W (2000) Granitic and gneissic outcrops (inselbergs) as centers of diversity for desiccation-tolerant vascular plants. Plant Ecol 151: 19–28[CrossRef] Pressel S, Ligrone R, Duckett JG (2006) Effects of de- and rehydration on food-conducting cells in the moss Polytrichum formosum: a cytological study. Ann Bot (Lond) 98: 67–76 Proctor M (2001) Patterns of desiccation tolerance and recovery in bryophytes. Plant Growth Regul 35: 147–156[CrossRef][Web of Science] Proctor MC, Smirnoff N (2000) Rapid recovery of photosystems on rewetting desiccation-tolerant mosses: chlorophyll fluorescence and inhibitor experiments. J Exp Bot 51: 1695–1704 Proctor MCF, Ligrone R, Duckett JG (2007) Desiccation tolerance in the moss Polytrichum formosum: physiological and fine-structural changes during desiccation and recovery. Ann Bot (Lond) 99: 75–93 Proctor MCF, Tuba Z (2002) Poikilohydry and homoihydry: antithesis or spectrum of possibilities? New Phytol 156: 327–349[CrossRef][Web of Science] Quatrano RS, McDaniel SF, Khandelwal A, Perroud PF, Cove DJ (2007) Physcomitrella patens: mosses enter the genomic age. Curr Opin Plant Biol 10: 182–189[CrossRef][Web of Science][Medline] Rensing SA, Lang D, Zimmer AD, Terry A, Salamov A, Shapiro H, Nishiyama T, Perroud PF, Lindquist EA, Kamisugi Y, et al (2008) The Physcomitrella genome reveals evolutionary insights into the conquest of land by plants. Science 319: 64–69 Rothman JE (1989) Polypeptide chain binding proteins: catalysts of protein folding and related processes in cells. Cell 59: 591–601[CrossRef][Web of Science][Medline] Shen S, Jing Y, Kuang T (2003) Proteomics approach to identify wound-response related proteins from rice leaf sheath. Proteomics 3: 527–535[CrossRef][Web of Science][Medline] Smirnoff N (1992) The carbohydrates of bryophytes in relation to desiccation tolerance. J Bryol 17: 185–191[Web of Science] Smirnoff N (1998) Plant resistance to environmental stress. Curr Opin Biotechnol 9: 214–219[CrossRef][Web of Science][Medline] Smith LG (2003) Cytoskeletal control of plant cell shape: getting the fine points. Curr Opin Plant Biol 6: 63–73[CrossRef][Web of Science][Medline] Theil EC (1987) Ferritin: structure, gene regulation, and cellular function in animals, plants, and microorganisms. Annu Rev Biochem 56: 289–315[CrossRef][Web of Science][Medline] Tuba Z, Lichtenthaler HK, Csintalan Z, Nagy Z, Szente K (1996) Loss of chlorophylls, cessation of photosynthetic CO2 assimilation and respiration in the poikilochlorophyllous plant Xerophyta scabrida during desiccation. Physiol Plant 96: 383–388[CrossRef] Tuba Z, Lichtenthaler HK, Maroti I, Zs C (1993) Resynthesis of thylakoids and functional chloroplasts in the desiccated leaves of the poikilochlorophyllous plant Xerophyta scabrida upon rehydration. J Plant Physiol 142: 742–748[Web of Science] Tuba Z, Proctor MCF, Csintalan Z (1998) Ecophysiological responses of homoiochlorophyllous and poikilochlorophyllous desiccation tolerant plants: a comparison and an ecological perspective. Plant Growth Regul 24: 211–217[CrossRef][Web of Science] Tuba Z, Smirnoff N, Csintalan Z, Szente K, Nagy Z (1997) Respiration during slow desiccation of the poikilochlorophyllous desiccation tolerant plant Xerophyta scabrida at present-day CO2 concentration. J Plant Physiol Biochem 35: 381–386 Tunnacliffe A, Wise MJ (2007) The continuing conundrum of the LEA proteins. Naturwissenschaften 94: 791–812[CrossRef][Web of Science][Medline] Wang W, Vinocur B, Shoseyov O, Altman A (2004) Role of plant heat-shock proteins and molecular chaperones in the abiotic stress response. Trends Plant Sci 9: 244–252[CrossRef][Web of Science][Medline] Wang X, Yang P, Gao Q, Liu X, Kuang T, Shen S, He Y (2008) Proteomic analysis of the response to high-salinity stress in Physcomitrella patens. Planta 228: 167–177[CrossRef][Web of Science][Medline] Weng JK, Tanurdzic M, Chapple C (2005) Functional analysis and comparative genomics of expressed sequence tags from the leucophyte Selaginella moellendorfii. BMC Genomics 6: 85[CrossRef][Medline] Wood AJ (2005) Eco-physiological adaptations to limited water environments. In PM Haegawa, MA Jenks, eds, Plant Abiotic Stress. Blackwell Press, Oxford, pp 1–13 Wood AJ (2007) Frontiers in bryological and lichenological research: the nature and distribution of vegetative desiccation tolerance in hornworts, liverworts and mosses. Bryologist 110: 163–177[CrossRef] Zhu B, Choi DW, Fenton R, Close TJ (2000) Expression of the barley dehydrin multigene family and the development of freezing tolerance. Mol Gen Genet 264: 145–153[CrossRef][Web of Science][Medline]
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ABSTRACT
RESULTS
-glucan water dikinase (spot I62), transketolase (spot U33), rhamnose biosynthetic enzyme 1 (spot U43), fructokinase (spots U44 and U45), and glyceraldehyde-3- phosphate dehydrogenase (spots U47 and I64). 
Cn score of at least 0.1 (regardless of charge state). Peptides with a +1 charge state were accepted if they were fully tryptic digested and had a cross-correlation (Xcorr) of at least 1.9. Peptides with a +2 charge state were accepted if they had an Xcorr of 2.2 or greater. Peptides with a +3 charge state were accepted if they had an Xcorr of 3.75 or greater.