An osmotin (CpOsm) from the latex of Calotropis procera has been crystallized in both tetragonal and trigonal forms suitable for structure determination. Crystallographic studies of CpOsm are of ...great interest because limited information is available concerning the structure of latex proteins and CpOsm has previously been shown to interact with the spore membranes of some plant pathogenic fungi, thus impairing spore germination and hyphal growth. CpOsm crystals were grown using 0.1 M HEPES buffer pH 7.5, 26% PEG 4000, 0.2 M ammonium sulfate (space group P43) or using 0.1 M HEPES buffer pH 7.5, 35% MPD, 0.7 M ammonium sulfate (space group P3112). X‐ray diffraction data were collected to 2.17 Å (P43) and 1.80 Å (P3112) resolution and molecular‐replacement analyses produced initial phases for both crystal forms.
The specificity and kinetics of the interaction between the pathogenesis-related group of thaumatin-like proteins (PR5) in higher plants and (1,3)-beta-D-glucans have been investigated. Two ...thaumatin-like proteins with 60% amino-acid sequence identity were purified from extracts of germinated barley grain, and were designated HvPR5b and HvPR5c. Purified HvPR5c interacted with insoluble (1,3)-beta-D-glucans, but not with cellulose, pustulan, xylan, chitin or a yeast mannoprotein. Tight binding was observed with unbranched and unsubstituted (1,3)-beta-D-glucans, and weaker binding was seen if (1,6)-beta-linked branch points or beta-glucosyl substituents were present in the substrate. The HvPR5b protein interacted weakly with insoluble (1,3)-beta-D-glucans and did not bind to any of the other polysaccharides tested. This indicated that only specific barley PR5 isoforms interact tightly with (1,3)-beta-D-glucans. The complete primary structures of HvPR5b and HvPR5c were determined and used to construct molecular models of HvPR5b and HvPR5c, based on known three-dimensional structures of related thaumatin-like proteins. The models were examined for features that may be associated with (1,3)-beta-D-glucan binding, and a potential (1,3)-beta-D-glucan-binding region was located on the surface of HvPR5c. No obvious structural features that would prevent binding of (1,3)-beta-D-glucan to HvPR5b were identified, but several of the amino acids in HvPR5c that are likely to interact with (1,3)-beta-D-glucans are not present in HvPR5b.
The specificity and kinetics of the interaction between the pathogenesis‐related group of thaumatin‐like proteins (PR5) in higher plants and (1,3)‐β‐d‐glucans have been investigated. Two ...thaumatin‐like proteins with 60% amino‐acid sequence identity were purified from extracts of germinated barley grain, and were designated HvPR5b and HvPR5c. Purified HvPR5c interacted with insoluble (1,3)‐β‐d‐glucans, but not with cellulose, pustulan, xylan, chitin or a yeast mannoprotein. Tight binding was observed with unbranched and unsubstituted (1,3)‐β‐d‐glucans, and weaker binding was seen if (1,6)‐β‐linked branch points or β‐glucosyl substituents were present in the substrate. The HvPR5b protein interacted weakly with insoluble (1,3)‐β‐d‐glucans and did not bind to any of the other polysaccharides tested. This indicated that only specific barley PR5 isoforms interact tightly with (1,3)‐β‐d‐glucans. The complete primary structures of HvPR5b and HvPR5c were determined and used to construct molecular models of HvPR5b and HvPR5c, based on known three‐dimensional structures of related thaumatin‐like proteins. The models were examined for features that may be associated with (1,3)‐β‐d‐glucan binding, and a potential (1,3)‐β‐d‐glucan‐binding region was located on the surface of HvPR5c. No obvious structural features that would prevent binding of (1,3)‐β‐d‐glucan to HvPR5b were identified, but several of the amino acids in HvPR5c that are likely to interact with (1,3)‐β‐d‐glucans are not present in HvPR5b.
Eight mulberry genotypes were screened for drought resistance potential by withholding water. Based on leaf yield, nutrient analyses (total soluble proteins, sugars, free amino acids, total lipids ...and sterols) and such drought resistant characters as stomatal frequency, cuticle thickness, epicuticular wax content, chlorophyll stability index, as well as water-related parameters (leaf water potential, relative water content, water loss and moisture retention capacity), the following mulberry genotypes are recommended for rain-fed conditions in the following hierarchy, S-13>S-34>BC2-59>MR-2>S-14>Tr-4>Kosen>M-5. S-13 and S-34 were found to maintain higher leaf water potential, nutrients and osmotins under stress conditions, producing higher leaf yield, and these genotypes are recommended for plantation in hot and arid conditions. Over production of osmotins such as proline or glycine betaine by two to three-fold is indicative of a positive and significant correlation to injury due to stress as these two osmotins were found to increase in both water deficit-susceptible and resistant mulberry genotypes.
Plants have evolutionarily established resistance responses to a variety of abiotic stress conditions, in which ABA mediates the integrated regulation of these stress responses. Numerous proteins ...function at the transcription level or at the protein level when contributing to controls of the ABA signaling process. Although osmotin is identified as a salt-inducible protein, its function in the abiotic stress response is yet to be elucidated. To examine the role of Arabidopsis OSMOTIN 34 (OSM34) in the ABA signaling pathway, a deletion mutant osm34 generated by a CRISPR/Cas9 system and the double mutant osm34 osml (osmotin 34-like) were analyzed for various ABA responses. Both osm34 and osm34 osml showed reduced levels of ABA responses in seeds and leaves. Moreover, proline level and expression of the proline biosynthesis gene P5CS1 was significantly reduced in osm34 osml. Interestingly, OSM34 binds to SKP2A, an F-Box protein whose transcription is induced by ABA. The protein stability of OSM34 was determined to be under the control of the 26S proteasome. In conclusion, our data suggest that OSM34 functions as a positive regulator in the generation of ABA responses and is under post-translational control.
Plants are recurrently exposed to myriads of biotic and abiotic stresses leading to several biochemical and physiological variations that cause severe impacts on plant growth and survival. To ...overcome these challenges, plants activate two primary defense mechanisms, such as structural response (cell wall strengthening and waxy epidermal cuticle development) and metabolic changes, including the synthesis of anti-microbial compounds and proteins, especially the pathogenesis-related (PR) proteins. PR proteins are members of a super large family of defense proteins that exhibit antimicrobial activities. Their over-expression in plants provides tolerance to many abiotic and biotic stresses. PR proteins have been classified into 17 families, including PR-5–also called thaumatin-like proteins (TLPs) that involve osmotin and osmotin-like proteins (OLPs). Osmotin was first identified in tobacco (Nicotiana tabacum var. Wisconsin 38), and then its homolog proteins (OLPs) were reported from the whole plant kingdom. Osmotin and OLPs are ubiquitous in all fruits and vegetables. Their expression has been detected in various plant tissues and organs. The phylogenetic tree studies revealed that the osmotin group originated from spermatophytes. Moreover, the atomic structure of OLP has shown similarity to thaumatin and TLPs from monocot and eudicot species, which determines a strong evolutionary pressure in flowering plants for conserving thaumatin fold. This is associated with the role of these proteins against pathogens as defense molecules and to induce stress tolerance to plants against several biotic and abiotic factors. In this review, we have briefly described the development history of osmotin, including its function and mechanism to induce biotic and abiotic stress tolerance to plants.
•Osmotin, which plays an important role in the response to stresses, displays expression in the micropylar region of tomato seed endosperm.•SlNP24 expression coincides with the potential upstream ...regulator TERF1.•SlNP24 and TERF1 expression is induced by ethylene and methyl jasmonate in germinating tomato seeds.
The expression of SlNP24 encoding osmotin was studied in germinating tomato seeds Solanum lycopersicum L. cv. Moneymaker. The results show that the accumulation of the transcripts of SlNP24 and its potential upstream regulator TERF1 encoding an ethylene response factor was induced by ethylene and methyl jasmonate in germinating tomato seeds. There was no effect of gibberellins on the expression of the genes studied. The expression of SlNP24 was localized in the micropylar region of the endosperm of tomato seeds. The promoter of tomato osmotin was active in the endosperm cells of transgenic Arabidopsis thaliana seeds, which contain reporter genes under control of SlNP24 promoter. The activity of SlNP24 promoter in A. thaliana reporter line seeds was visible when the expression of its ortholog gene in A. thaliana (AtOMS34) was observed. The mechanism of induction and a possible role of NP24 in germinating tomato seeds are discussed.
Salinity stress is considered the most devastating abiotic stress for crop productivity. Accumulating different types of soluble proteins has evolved as a vital strategy that plays a central ...regulatory role in the growth and development of plants subjected to salt stress. In the last two decades, efforts have been undertaken to critically examine the genome structure and functions of the transcriptome in plants subjected to salinity stress. Although genomics and transcriptomics studies indicate physiological and biochemical alterations in plants, it do not reflect changes in the amount and type of proteins corresponding to gene expression at the transcriptome level. In addition, proteins are a more reliable determinant of salt tolerance than simple gene expression as they play major roles in shaping physiological traits in salt-tolerant phenotypes. However, little information is available on salt stress-responsive proteins and their possible modes of action in conferring salinity stress tolerance. In addition, a complete proteome profile under normal or stress conditions has not been established yet for any model plant species. Similarly, a complete set of low abundant and key stress regulatory proteins in plants has not been identified. Furthermore, insufficient information on post-translational modifications in salt stress regulatory proteins is available. Therefore, in recent past, studies focused on exploring changes in protein expression under salt stress, which will complement genomic, transcriptomic, and physiological studies in understanding mechanism of salt tolerance in plants. This review focused on recent studies on proteome profiling in plants subjected to salinity stress, and provide synthesis of updated literature about how salinity regulates various salt stress proteins involved in the plant salt tolerance mechanism. This review also highlights the recent reports on regulation of salt stress proteins using transgenic approaches with enhanced salt stress tolerance in crops.
Osmotin and osmotin-like proteins (OLPs) play important roles in plant defense responses. The full-length cDNA sequence of an OLP gene was cloned from Panax notoginseng using rapid amplification of ...cDNA-end technology and named PnOLP1. A qRT-PCR analysis showed that the signaling molecules methyl jasmonate, salicylic acid, ethylene, and hydrogen peroxide induced PnOLP1 expression to different degrees. In addition, the expression level of PnOLP1 rapidly increased within 48 h of inoculating P. notoginseng with the root-rot pathogen Fusarium solani. Subcellular localization revealed that PnOLP1 localized to the cell wall. A prokaryotic expression vector containing PnOLP1 was constructed and transformed into Escherichia coli BL21 (DE3), and in vitro antifungal assays were performed using the purified recombinant PnOLP1 protein. The recombinant PnOLP1 protein had strong inhibitory effects on the mycelial growth of F. oxysporum, F. graminearum, and F. solani. A plant PnOLP1-overexpression vector was constructed and transfected into tobacco, and the resistance of T2 transgenic tobacco against F. solani was significantly enhanced compared with wild type tobacco. Moreover, a PnOLP1 RNAi vector was constructed and transferred to the P. notoginseng leaves for transient expression, and the decrease of PnOLP1 expression level in P. notoginseng leaves increased the susceptibility to F. solani. Thus, PnOLP1 is an important disease-resistance gene involved in the defense responses of P. notoginseng to F. solani.
Osmotin-like proteins (OLPs), of PR-5 family, mediate defense against abiotic, and biotic stresses in plants. Overexpression in sesame of an OLP gene (
), enhanced tolerance against drought, ...salinity, oxidative stress, and the charcoal rot pathogen. SindOLP was expressed in all parts and localized to the cytosol. The transgenic plants recovered after prolonged drought and salinity stress, showing less electrolyte leakage, more water content, longer roots, and smaller stomatal aperture compared to control plants. There was an increase in osmolytes, ROS-scavenging enzymes, chlorophyll content, proline, secondary metabolites, and reduced lipid peroxidation in the transgenic sesame under multiple stresses. The OLP gene imparted increased tolerance through the increased expression of three genes coding for ROS scavenging enzymes and five defense-related marker genes functioning in the JA/ET and SA pathways, namely
, and
were monitored. The transgenic lines showed greater survival under different stresses compared to control through the integrated activation of multiple components of the defense signaling cascade. This is the first report of transgenic sesame and first of any study done on defense-related genes in sesame. This is also the first attempt at understanding the molecular mechanism underlying multi-stress tolerance imparted by an OLP.
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