Dehydrin-like Proteins Research Articles

Detection of dehydrin-like proteins in embryos and endosperm of mature Euterpe edulis seeds

Euterpe edulis Martius, a tropical palm species characterized as highly recalcitrant, accumulated dehydrin proteins in both the endosperm and the embryo of the mature seed, as detected by Western blot analysis and immunogold electron microscopy. Three major bands at molecular masses of approximately 16, 18, and 24 kDa were identified in both samples analysed. Immunogold electron microscopy studies detected the presence of dehydrins in the embryo and endosperm. In both cases, dehydrins were immunolocalized in cytoplasm and chromatin. No labelling associated with either membranes or organelles was detected. It is known that dehydrins are produced as part of the developmental program of orthodox seeds and are also present in some recalcitrant seeds of temperate regions. The constitutive presence of dehydrins in embryos of extremely recalcitrant species of tropical origin has not been previously reported.

Salicylic Acid Decreases the Levels of Dehydrin-Like Proteins in Tibetan Hulless Barley Leaves under Water Stress

The effects of salicylic acid (SA) on the accumulation of dehydrins in leaves of Tibetan hulless barley seedlings under water stress were investigated. The results indicated that SA decreased the levels of the four dehydrin-like proteins induced by water stress. The concentrations of these dehydrin-like proteins increased under water stress. However, their levels in SA-pretreated seedlings were always lower than in those receiving only water stress. Our results also indicated that the levels of dehydrin-like proteins decreased as the SA concentration increased. In SA-pretreated seedlings, electrolyte leakage, MDA and H2O2 content were rather higher than in seedlings receiving only water stress. By these results, we suggest that lower levels of dehydrin-like proteins in seedlings with SA treatment may be due to the greater accumulation of H2O2 induced by SA, which causes more oxidative injury under water stress.

Seasonal changes in photosynthesis, protein composition and mineral content in Rhododendron leaves

Seasonal changes in the proteome, specific leaf weight, mineral content, pigment content and photosynthetic properties were determined in leaves of a cultivar of Rhododendron catawbiense harvested in the field (2001–2004). Two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) revealed that several dehydrin-like proteins, strongly expressed in the winter acclimated samples, disappeared during the transition to spring. Photosynthetic carbon assimilation, electron transport and the quantum yield for photosystem II ( F v/ F m) were severely down-regulated in winter acclimated leaves. Xanthophyll cycle pigments increased 2.3-fold in winter acclimated leaves. When winter acclimated leaves were brought into more favorable temperature conditions, the capacity of carbon assimilation fully recovered over a period of approximately 14 days. The recovery was linear and rapid for the first 4 days yielding 60% of the fully recovered rate. Electron transport rates (ETR) recovered more rapidly (80% recovery in 24 h) than carbon assimilation. The linear phase of the ETR recovery was slightly inhibited by protein synthesis inhibitors streptomycin and chloramphenicol, but more markedly by cycloheximide (44% inhibition). The slow recovery phase was impacted by all of the protein synthesis inhibitors with cycloheximide having the most profound effect (58% inhibition at 48 h). Specific leaf weight increased by 48% in winter acclimated leaf samples relative to late summer. Leaf calcium and magnesium contents were reduced (24% and 17%, respectively) in winter relative to late summer samples. An opposite pattern was seen for sulfur and phosphate (winter increases of 28% for sulfur and 72% for phosphate).

Induction of tolerance to desiccation and cryopreservation in silver maple (Acer saccharinum) embryonic axes

Twenty percent of of the world's flowering plants produce recalcitrant seeds (i.e., seeds that cannot withstand drying or freezing). We investigated whether the embryonic axis from the normally recalcitrant seeds of silver maple (Acer saccharinum L.) can be made tolerant to desiccation (10% water content) and low temperature (-196 degrees C, cryopreservation) by pretreatment with ABA or the compound tetcyclacis, which enhances endogenous ABA concentrations. Pretreatment of axes with both ABA and tetcyclacis increased germination after desiccation and freezing to 55% from a control value of zero. Pretreatment of axes with ABA and tetcyclacis increased the ABA content of the axes, as measured by enzyme-linked immunoassay, and stimulated the synthesis of storage and dehydrin-like proteins, believed to have a role in the desiccation tolerance of orthodox seeds.

Differential accumulation of dehydrin-like proteins by abiotic stresses in Deschampsia antarctica Desv.

Dehydrins are proteins that accumulate during environmental stresses leading to cell dehydration. Deschampsia antarctica is one of the two vascular plants that have colonized the Maritime Antarctic. This plant is usually exposed to cold, salt and desiccating winds in the field. We proposed that among the factors that allow D. antarctica to survive the harsh environmental conditions is the presence of dehydrins. We studied the accumulation of dehydrins by abscisic acid (ABA), dehydration, NaCl and low osmotic potential. Western blots using an anti-dehydrin antibody revealed a complex pattern of dehydrin-like proteins (DLPs) accumulation in the different treatments. DLPs with apparent molecular weight of 58, 57, 55, 53, 48, 42, 32, 30, 28 and 25 kDa were detected in the different treatments. DLPs accumulation was associated with a decrease in the relative water content (RWC) of the plants. These results suggest that DLPs accumulation could contribute to explain how D. antarctica can survive under adverse Antarctic conditions.

Synthesis of dehydrin-like proteins in Quercus ilex L. and Quercus cerris L. seedlings subjected to water stress and infection with Phytophthora cinnamomi

The synthesis of dehydrin-like proteins in 24-month-old Quercus cerris and Q. ilex seedlings subjected to water stress and/or infection with Phytophthora cinnamomi, was investigated. An estimated 50 kDa dehydrin-like protein was observed in leaves of symptomless Q. ilex (drought tolerant) in control, as well as in seedlings infected with P. cinnamomi, throughout the experiment. Water stress, with a midday stem water potential value lower than −2.7 MPa (up to 8 weeks), increased band intensity. Two new polypeptides with a molecular weight of about 60 and 63 kDa, respectively, were detected in Q. ilex, under enhanced water stress conditions (≤−4.0 MPa). No dehydrin-like proteins were observed in leaves of symptomless Q. cerris (drought susceptible) neither in control nor in infected treatments. With a midday stem water potential lower than −3.8 MPa (up to 7 weeks), water stress induced the synthesis of a protein with an approx. molecular weight of 43 kDa, while a band of about 36.5 kDa was detected for both water stress and infection treatments. These results suggest the involvement of dehydrin-like proteins in the response of Q. ilex and Q. cerris seedlings to different stresses.

Phylogenetic analyses in cornus substantiate ancestry of xylem supercooling freezing behavior and reveal lineage of desiccation related proteins.

The response of woody plant tissues to freezing temperature has evolved into two distinct behaviors: an avoidance strategy, in which intracellular water supercools, and a freeze-tolerance strategy, where cells tolerate the loss of water to extracellular ice. Although both strategies involve extracellular ice formation, supercooling cells are thought to resist freeze-induced dehydration. Dehydrin proteins, which accumulate during cold acclimation in numerous herbaceous and woody plants, have been speculated to provide, among other things, protection from desiccative extracellular ice formation. Here we use Cornus as a model system to provide the first phylogenetic characterization of xylem freezing behavior and dehydrin-like proteins. Our data suggest that both freezing behavior and the accumulation of dehydrin-like proteins in Cornus are lineage related; supercooling and nonaccumulation of dehydrin-like proteins are ancestral within the genus. The nonsupercooling strategy evolved within the blue- or white-fruited subgroup where representative species exhibit high levels of freeze tolerance. Within the blue- or white-fruited lineage, a single origin of dehydrin-like proteins was documented and displayed a trend for size increase in molecular mass. Phylogenetic analyses revealed that an early divergent group of red-fruited supercooling dogwoods lack a similar protein. Dehydrin-like proteins were limited to neither nonsupercooling species nor to those that possess extreme freeze tolerance.

Characterization of a Novel YnSKn Class of Dehydrin-Like cDNAs from Cold Acclimated Red-Osier Dogwood (Cornus sericea L.) Xylem

Summary Red-osier dogwood (Cornus sericea L.) is among the most freeze-tolerant plant species. Four cDNAs were isolated from cold acclimated red-osier dogwood xylem and found to encode novel dehydrin-like proteins. The four deduced amino acid sequences were extremely hydrophilic and contained sequence motifs characteristic of the dehydrin family. ROD (red-osier dehydrin) 44, 48 and 60 sequences each contained the Y, S, and K motifs characteristic of dehydrins. Whereas ROD 25 contained the Y and S motifs but lacked the lysine-rich repeat (K segment). A unique aspect of these sequences was that ROD 25, 44, 48 and 60 included 14, 33, 33 and 35 copies, respectively, of a sequence similar to DEYGNP. This is quite different from other dehydrin-like proteins, which typically contained only one to three Y motifs. The function of these highly repeated sequences is not known. Alignment of the deduced amino acid sequences of ROD 44 and ROD 48 revealed 69% identity. Alignment of overlapping regions of ROD 25 and ROD 60 revealed 89% identity. Transcript expression of Rod genes changed seasonally in red-osier dogwood and was correlated to periods of cold acclimation.

Dehydrin variability among rhododendron species: a 25‐kDa dehydrin is conserved and associated with cold acclimation across diverse species

• Here we examine the accumulation pattern of dehydrins in non- vs cold-acclimated leaves of 21 species comprising two divergent groups of Rhododendron, Subgenus Hymenanthes and Subgenus Rhododendron. Individuals from five other Ericaceous genera were also evaluated in the same way. Quantitative comparisons of cold-inducibility of a 25-kDa dehydrin and cold acclimation ability in six Rhododendron species were also performed. • Leaf freezing tolerance assay and dehydrin detection and quantification were performed as previously described. • Eleven dehydrins, ranging from 25- to 73-kDa, were observed among the 21 species, and most were more abundant in winter-collected leaves than in summer-collected leaves. One dehydrin, a 25-kDa protein, was uniquely conserved across most (95%) of the species surveyed, and was absent only in R. brookeanum, a tropical species that may not be capable of cold acclimation. The 25-kDa dehydrin was also identified in Kalmia, a genus closely related to Rhododendron but not in four other less related Ericaceous genera. Comparison of dehydrin profiles in non- and cold-acclimated leaf tissue from six species (three very hardy, and three less hardy, species) indicated a close association (R2 =0.95) between relative changes in leaf freezing tolerance and 25-kDa dehydrin accumulation. • The taxonomic and physiological comparisons suggest a central, but as yet unknown, function for the 25-kDa dehydrin in protecting rhododendron leaves from freezing injury.

Novel plasmodesmata association of dehydrin-like proteins in cold- acclimated Red-osier dogwood (Cornus sericea).

Dehydrins are proteins associated with conditions affecting the water status of plant cells, such as drought, salinity, freezing and seed maturation. Although the function of dehydrins remains unknown, it is hypothesized that they stabilize membranes and macromolecules during cellular dehydration. Red-osier dogwood (Cornus sericea L.), an extremely freeze-tolerant woody plant, accumulates dehydrin-like proteins during cold acclimation and the presence of these proteins is correlated with increased freeze tolerance (Karlson 2001, Sarnighausen et al. 2002, Karlson et al. 2003). Our objective was to determine the location of dehydrins in cold-acclimated C. sericea stems in an effort to provide insight into their potential role in the freeze tolerance of this extremely cold hardy species. Abundant labeling was observed in the nucleus and cytoplasm of cold-acclimated C. sericea stem cells. In addition, labeling was observed in association with plasmodesmata of cold-acclimated vascular cambium cells. The unique association of dehydrin-like proteins with plasmodesmata has not been reported previously.

Accumulation of dehydrin-like proteins in the mitochondria of cereals in response to cold, freezing, drought and ABA treatment

BackgroundDehydrins are known as Group II late embryogenesis abundant proteins. Their high hydrophilicity and thermostability suggest that they may be structure stabilizers with detergent and chaperone-like properties. They are localised in the nucleus, cytoplasm, and plasma membrane. We have recently found putative dehydrins in the mitochondria of some cereals in response to cold. It is not known whether dehydrin-like proteins accumulate in plant mitochondria in response to stimuli other than cold stress.ResultsWe have found five putative dehydrins in the mitochondria of winter wheat, rye and maize seedlings. Two of these polypeptides had the same molecular masses in all three species (63 and 52 kD) and were thermostable. Drought, freezing, cold, and exogenous ABA treatment led to higher accumulation of dehydrin-like protein (dlp) 63 kD in the rye and wheat mitochondria. Protein 52 kD was induced by cold adaptation and ABA. Some accumulation of these proteins in the maize mitochondria was found after cold exposition only. The other three proteins appeared to be heat-sensitive and were either slightly induced or not induced at all by all treatments used.ConclusionsWe have found that, not only cold, but also drought, freezing and exogenous ABA treatment result in accumulation of the thermostable dehydrins in plant mitochondria. Most cryotolerant species such as wheat and rye accumulate more heat-stable dehydrins than cryosensitive species such as maize. It has been supposed that their function is to stabilize proteins in the membrane or in the matrix. Heat-sensitive putative dehydrins probably are not involved in the stress reaction and adaptation of plants.

Effects of desiccation on peanut ( Arachis hypogaea L.) seed protein composition

Response of peanut to desiccation was studied by monitoring changes in the seed protein content and composition during a 14 day desiccation period using a combination of electrophoretic and immunochemical techniques. Following desiccation, the protein content of ‘white’ (most immature) and ‘orange’ seed increased, while that of the ‘brown’ (mature) seed was not affected. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) showed no major qualitative differences in the protein composition during desiccation of the samples. However, immunoblotting with anti-dehydrin antisera revealed the presence of several new proteins in the desiccated samples compared with the controls. One of the dehydrin-like proteins, band ‘c’ was found to be related to water-stress, while the other proteins appeared to be the storage proteins accumulated as the seed matured in vitro. Capillary electrophoresis (CE) showed major changes in the protein quantity and quality of ‘white’ seed during the 0–14 days of desiccation. In contrast, in the ‘orange’ and ‘brown’ seeds changes in protein composition were less significant. Results indicated that there are several dehydrin-like proteins expressed in peanuts, however, not all of them are related to water stress.

Putative desiccation tolerance mechanisms in orthodox and recalcitrant seeds of the genusAcer

AbstractRecalcitrant seeds are shed moist from the plant and do not survive desiccation to the low moisture contents required for prolonged storage. It has been widely hypothesised that during desiccation of these seeds a stress induced metabolic imbalance develops that leads to free radical mediated damage and viability loss. We investigated this hypothesis in a comparison of two sympatric species ofAcerduring late seed development and post-harvest desiccation:A. platanoides(Norway maple) has orthodox seeds andA. pseudoplatanus(sycamore) has recalcitrant seeds. In both species, respiration rates declined to similar levels at shedding, and the extent of defences against free radicals appears no less in sycamore than that in Norway maple. During drying there was no evidence for the accumulation of a stable free radical, increased lipid peroxidation or decline in free radical scavenging enzymes in either species. In addition, there was a very similar, large increase in total tocopherol in both species. This increase in sycamore was largely of alpha-tocopherol, whereas in Norway maple the increase was largely from its precursor, gamma-tocopherol. Arguably this suggests a similar mechanism in both species, but increased oxidative stress in sycamore. In general, the results suggest that, although damage resulting in viability loss was clearly taking place, the limitation to desiccation tolerance did not result from inadequate free radical scavenging. Soluble carbohydrates and dehydrin-like proteins were also measured during late seed development and drying in sycamore and Norway maple. The greater concentrations of sucrose, raffinose and stachyose and amounts of dehydrins in the radicles and cotyledons of Norway maple compared with those in sycamore was consistent with greater desiccation tolerance in the former. Sycamore seeds are dormant and at the tolerant end of the continuum of desiccation sensitivity among recalcitrant species, and this may account for their different response to that of the seeds of other more sensitive recalcitrant species studied.

Accumulation of Dehydrin-like-proteins in the Mitochondria of Cold-treated Plants

Summary A number of proteins have been found to accumulate in plants during cold tolerance. One class of cold proteins that is associated with cold tolerance acclimation is the glycine-rich, hydrophilic, D-II LEA (late embryogenesis abundant) proteins known as dehydrins. Several members of the dehydrin-class of proteins are known to associate with the nucleus, in the cytosol, and with the plasma membrane. Dehydrins that localise with the mitochondria have not been found. We provide evidence that two dehydrin-like proteins (dlps) accumulate in the mitochondria only after low temperature treatment. We also provide evidence for a positive correlation between the relative accumulation of these proteins in the mitochondria in response to cold stress and relative cold tolerance of several species of plants.

Gamete Release at Low Tide in Fucoid Algae: Maladaptive or Advantageous?

This review discusses three questions pertaining to gamete release by fucoid algae at low tide: 1) Are gametes viable and does fertilization occur at low tide?, 2) How many gametes are released at low tide versus at high tide? and 3) Is gamete release at low tide maladaptive or is it selectively advantageous? Gamete release at low tide (LT) in fucoid algae is observed commonly in monoecious species from the lower and mid-intertidal zones ( e.g., Fucus distichus, F. evanescens, F. gardneri, Pelvetia compressa ); in dioecious species, intact antheridia (containing sperm) are commonly released at low tide ( e.g. , in Ascophyllum nodosum, F. vesiculosus ). Fertilization at low tide can be determined with a calcofluor white assay and occurs in at least three species ( F. distichus, F. gardneri, P. compressa ). In general, fucoid algae have high levels of fertilization success, but substantial mortality occurs during early embryogenesis in some intertidal zones due to physical stresses. The agarose bead assay is useful to assess desiccation on an egg-sized scale. Constitutive dehydrin-like proteins are present in sperm, eggs, and embryos. The release of gametes at low tide appears to be a consequence of a mechanism selected to permit gamete release under calm conditions in seawater; this mechanism is described. The timing of adhesion by zygotes at low and high tide is unknown. Such information and additional data on the relative proportions of zygotes produced by monecious species at low tide versus high tide are required in order to assess effects of gamete release at low tide upon dispersal and population structure.

Inflorescence bud protease(s) against dehydrin-like inflorescence bud proteins of Pistacia vera

This paper reports on a proteolytic activity extracted from Pistacia vera L. (pistachio) inflorescence buds, found in male and female tissues. The proteolytic activity reaches a peak at the beginning of bud opening and flowering and is directed against inflorescence bud dehydrin-like proteins of pistachio, IBP32 and IBP27. The effect of protease inhibitors indicated that the protease(s) belong to a serine-protease-like family and are not cysteine, acid or metallo-proteases. The proteolytic activity was strongly inhibited by Nα- p-tosyl-L-lysine chloromethyl ketone and to a lesser extent by N-tosyl-L-phenylalanine chloromethyl ketone, suggesting mainly trypsin-like specificity or broader serine-protease specificity. It is suggested that the proteolytic activity is important in the mobilization of nitrogen reserves stored in the bud storage proteins during dormancy to support the fast-developing inflorescence in spring after bud dormancy break.

Identification of cDNAs from Cornus sericea that Encode a Family of Dehydrin-like Proteins

Three cDNAs, which apparently encode a family of dehydrin-like proteins, were isolated from cold-acclimating wood tissues of Cornus sericea. The nucleic acid sequences of these cDNAs are similar to each other (minimum 58% identical). Two of the cDNAs are predicted to encode proteins of 44 and 48.6 kDa. The third cDNA did not contain the complete open reading frame, but apparently encodes a much larger protein. The predicted amino acid sequences from all three cDNAs share homology with members of the dehydrin family of proteins. This family of proteins is characterized by the presence of a highly conserved lysine-rich consensus sequence (EKKGIMDKIKEKLPG) known as the K-segment, a tract of serine residues, and in most instances, an N-terminal consensus sequence (DEYGNP) designated as the Y-segment. The cDNAs isolated from C. sericea encode putative proteins with these common motifs. Each has a tract of serine residues, and either one or two lysine-rich segments. However, a unique feature of the cDNAs from C. sericea is that they encode putative proteins having 21, 24, and 27 repeated sequences similar to the Y-segment, whereas previously identified members of the dehydrin family exhibit only one to three such repeats. The significance of this difference is not known. Dehydrins have been implicated in desiccation tolerance, and typically accumulate in response to dehydrating conditions, such as occur during drought, salt-stress, low temperatures, and during the late stages of embryogenesis. In C. sericea, expression of these transcipts changed seasonally. Northern blot analysis detected high levels of transcript in October and January, and no detectable message in June.

Water Deficit in Pea Root Tips: Effects on the Cell Cycle and on the Production of Dehydrin-like Proteins

Abstract Dehydrin-like proteins have been detected in nuclei and cytoplasm of meristematic root tip cells from pea seedlings subjected to slow dehydration at 90% relative humidity for 48 h or more. Evidence was gained from Western blotting and immunocytochemical experiments using an antibody raised against the conserved domain of dehydrin proteins. Flow cytometer analysis has shown that cycling cells of root tip meristems from dehydrated seedlings are mostly arrested in G2 phase. Other stress treatments thought to involve water depletion (osmotic stress, cold treatment) or to modulate cell response to water deficit (abscisic acid) gave less clear-cut results with all treatments lowering the proportion of cells entering the S phase, but without a definite and persistent arrest in any preferential phase of the cycle. Possible interrelationships between G2 arrest and dehydrin production are discussed.

Water-stress response in aspen ( Populus tremula): Differential accumulation of dehydrin, sucrose synthase, GAPDH homologues, and soluble sugars

Summary In a previous study we identified a novel 66-kD boiling-stable protein (BspA) that accumulates in cultured shoots of aspen ( Populus tremula L.) in response to gradual water stress and ABA application, as well as to osmotic and cold stresses (Altman et al., 1996; Pelah et al., 1995). BspA was found to be the major heat-stable water stress-responsive protein in aspen. Here, the expression of other water-stress responsive proteins — DSP 16 (dehydrin), cytosolic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and sucrose synthase — was studied in aspen roots and shoots. These proteins were identified immunologically using polyclonal antibodies isolated from the resurrection plant Craterostigma plantagineum . A 43-kD homologue and a 31-kD homologue of dehydrin were found to accumulate in roots and shoots of aspen after water stress in a tissue specific manner. Shoots and roots of intact plantlets subjected to ABA application accumulated a 33-kD dehydrin homologue. A sucrose synthase homologue (90 kD) accumulated in water-stressed shoots and was constitutively present at high levels in control and water-stressed roots harvested from intact plandets. GAPDH, a key enzyme in the glycolysis and gluconeogenesis pathways, exhibited some accumulation in shoots in response to water stress. Sugar analysis revealed that water stress results in increased sucrose and decreased glucose levels in the aspen leaves. The data presented here suggest that the water-stress-response mechanisms present in herbaceous plants are also present in woody plants. Woody plants subjected to water stress accumulate dehydrin-like proteins and specific enzymes such as sucrose synthase and GAPDH, which may play a dominant role in sugar metabolism under these conditions.

Presence of dehydrin-like proteins and levels of abscisic acid in recalcitrant (desiccation sensitive) seeds may be related to habitat

AbstractThe presence of dehydrins could not be demonstrated in axes of mature, undried recalcitrant seeds of the tropical wetland species Avicennia marina, Barringtonia racemosa, Bruguiera exaristata, Bruguiera cylindrica, Bruguiera gymnorrhiza, Ceriops tagal, Rhizophora apiculata, Rhizophora mucronata and Rhizophora stylosa, but were present in the temperate species Acer saccharinum, Aesculus hippocastanum, Araucaria angustifolia, Camellia sinensis, Castanea sativa, Poncirus trifoliata and Zizania palustris. They were also present in axes of Castanospermum australe (of tropical origin) seeds which underwent development in a temperate climate, and were produced in response to drying in axes of Barringtonia racemosa but not Avicennia marina. The presence of dehydrins was associated with high abscisic acid contents. These proteins may provide protection against low temperatures in temperate seeds and against water loss to which the seeds may be naturally exposed. The presence of dehydrins was unrelated to the evolutionary status of the families studied.