Exploring the Mechanism of Physcomitrella patens Desiccation Tolerance through a Proteomic Strategy    

Abstract

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.

Desiccation sensitivity and tolerance in the moss Physcomitrella patens: assessing limits and damage

“…Water contents in this study are expressed on a dry matter basis, which reflects how much water remains to solvate and separate cellular contents, rather than the extent of water lost from the original hydrated tissue. In contrast, most previous studies of the dehydration tolerance of Physcomitrella have reported water loss in terms of fresh weight (Cuming et al 2007;Frank et al 2005;Pressel and Duckett 2010;Saavedra et al 2006;Wang et al 2009), which is common for measures of drought tolerance, but which may be less useful for studies of moss, whose fresh weight may include significant, but variable, amounts of surface water. In our studies, the initial water content of the colonies varied extensively; therefore, water losses corresponding to 90% of the fresh weight could leave from 0.2 to 2 g g dm -1 water remaining in the sample (e.g.…”

“…Desiccation tolerant cells survive the loss of all bulk water, plus the loss of interfacial water associated with macromolecular surfaces; this generally occurs at water contents less than about 0.1-0.3 g g dm -1 (dry matter) (Alpert 2005;Hoekstra et al 2001), although the precise value depends upon the composition of the cells (Walters and Koster 2007). Given these standard definitions, the description of Physcomitrella as desiccation tolerant (Wang et al 2009) merits closer investigation.…”

“…A recent paper (Wang et al 2009) claims that Physcomitrella is desiccation tolerant; the basis for this assertion is that the moss, grown and assessed on an agar medium, survived the loss of 90% of its fresh weight after lengthy exposure to air in a chamber containing silica gel. Defining Physcomitrella as desiccation tolerant contradicts previous reports that the moss cannot survive extensive water loss (Cuming et al 2007;Frank et al 2005;Saavedra et al 2006), nor can it survive equilibration to 35% RH (Oldenhof et al 2006).…”

Towards Understanding Abiotic Stress Signaling in Plants: Convergence of Genomic, Transcriptomic, Proteomic, and Metabolomic Approaches

“…Plants make adjustment at different levels of organization (molecular, cellular, tissue, organ, system, anatomical, morphological) to cope with stresses (Atkinson and Urwin 2012 ). Signaling and regulatory (transcription factors, phosphatases, kinases) mechanisms get activated under stress (Krasensky and Jonak 2012 ;Wang et al 2009 ). Various signaling processes involving calcium (Pan et al 2012 ;Reddy et al 2011 ), ROS (Ahmad et al 2010 ;Loiacono and De Tullio 2012 ), and kinase cascades (Baena-Gonzalez and Sheen 2008 ) are induced for signal transduction.…”

Proteomic profiling and redox status alteration of recalcitrant tea (Camellia sinensis) seed in response to desiccation

“…Protein spots were manually excised from the gel and ingel digestion by trypsin (Promega, Madison, WI, USA) was performed using the method of Wang et al (2009) with minor modifications. Gel slices were washed with 25% (v/v) ethanol and 7% (v/v) acetic acid for 12 h at room temperature, and destained with 50 mM NH 4 HCO 3 in 50% (v/v) methanol for 1 h at 40°C.…”