Two isoforms of a nucleotide-sugar pyrophosphatase/phosphodiesterase from barley leaves (Hordeum vulgare L.) are distinct oligomers of HvGLP1, a germin-like protein

OsGLP8-7 interacts with OsPRX111 to detoxify excess copper in rice

Lignin is a phenolic biopolymer generated from phenylpropanoid pathway in the secondary cell wall and is required for defense of plants against various stress. Although the fact of stress-induced lignin deposition has been clearly demonstrated, it remains largely elusive how the formation of lignin is promoted under Cu stress. The present study showed that OsGLP8-7, an extracellular glycoprotein of rice (Oryza sativa L.), plays an important function against Cu stress. The loss function of OsGLP8-7 results in Cu sensitivity whereas overexpression of OsGLP8-7 scavenges Cu-induced superoxide anion (O2•-). OsGLP8-7 interacts with apoplastic peroxidase111 (OsPRX111) and elevates OsPRX111 stability when exposed to excess Cu. In OsGLP8-7 overexpressing (OE) lines, the retention of Cu within cell wall limiting Cu uptake into cytoplasm is attributed to the enhanced lignification required for Cu tolerance. Exogenous application of a lignin inhibitor can impair the Cu tolerance of transgenic Arabidopsis lines overexpressing OsGLP8-7. In addition, co-expression of OsGLP8-7 and OsPRX111 genes in tobacco leaves leads to an improved lignin deposition compared to leaves expressing each gene individually or the empty vector. Taken together, our findings provided the convincing evidences that the interaction between OsGLP8-7 and OsPRX111 facilitates effectively lignin polymerization, thereby contributing to Cu tolerance in rice.

Oxalate in Plants: Metabolism, Function, Regulation, and Application

Characterized by strong acidity, chelating ability, and reducing ability, oxalic acid, a low molecular weight dicarboxylic organic acid, plays important roles in the regulation of plant growth and development, the response to both biotic and abiotic stresses such as plant defense and heavy metals detoxification, and food quality. The metabolism of oxalic acid has been well-studied in microorganisms, fungi, and animals but remains less understood in plants. However, excessive accumulation of oxalic acid is detrimental to plants. Therefore, the level of oxalic acid has to be precisely controlled in plant tissues. In this review, we summarize the metabolism, function, and regulation of oxalic acid in plants, and we discuss solutions such as agricultural practices and plant biotechnology to manipulate oxalic acid metabolism to regulate plant responses to both external stimuli and internal developmental cues.

Genetic dissection of quantitative traits loci identifies new genes for gelatinization parameters of starch and amylose-lipid complex (Resistant starch 5) in bread wheat

Starch is a major component of cereal grains such as wheat. Physicochemical and functional properties of starch affect end-use food quality and nutrients. To improve cultivars that preserve superior starch quality, the genetic foundation of the wheat starch and amylose-lipid complex (ALc, Resistant starch type 5) gelatinization are needed. This genome-wide association (GWA) mapping used 192 wheat genotypes (previously reported) to generate SNPs using an enhanced version of sequencing termed ddRAD on the Illumina Hi-seq X platform and 3696 high-quality influential SNPs were filtered out. The heterozygosity and Fst ranges in five subpopulations were 0.31-0.40 and 0.18-0.30 respectively. Nucleotide diversity and PIC ranged from 0.21 (6A) to 0.32 (2A) and 0.29 (6A) to 0.39 (4D) respectively. The Shannon waiver index was 1.7 and the whole-genome LD decay was 22 Mb at r² = 0.38. Following FDR, 23 and 8 SNPs showed association with starch properties in the year 2017 and 2018, respectively while 93 and 20 SNPs were associated with ALc gelatinization in the year 2017 and 2018 respectively. The identified potential new genes (GSK3-alpha, RING-type domain-containing protein, Tetratricopeptide repeat, Hexosyltransferase, GLP, SNF1, and WRKY transcription factor) within LD range (∼16 Kb to ∼15 Mb), BLUP value, and cis and trans-position of SNPs network provide valuable information for the future wheat breeding strategy for the improvement of the starch quality trait.

Characterization of Germin-like Proteins (GLPs) and Their Expression in Response to Abiotic and Biotic Stresses in Cucumber

Germins and germin-like proteins (GLPs) are glycoproteins closely associated with plant development and stress response in the plant kingdom. Here, we carried out genome-wide identification and expression analysis of the GLP gene family in cucumber to study their possible functions. A total of 38 GLP genes were identified in cucumber, which could be mapped to six out of the seven cucumber chromosomes. A phylogenetic analysis of the GLP members from cucumber, Arabidopsis and rice showed that these GLPs could be divided into six groups, and cucumber GLPs in the same group had highly similar conserved motif distribution and gene structure. Gene duplication analysis revealed that six cucumber GLP genes were located in the segmental duplication regions of cucumber chromosomes, while 14 genes were associated with tandem duplications. Tissue expression profiles of cucumber GLP genes showed that many genes were preferentially expressed in specific tissues. In addition, some cucumber GLP genes were differentially expressed under salt, drought and ABA treatments, as well as under DM inoculation. Our results provide important information for the functional identification of GLP genes in the growth, development and stress response of cucumber.

Potential stress tolerance roles of barley germins and GLPs

Germins and germin-like proteins (GLPs) known as germination markers are encoded by multigene families in several plant species, including barley. To date, functional analysis has revealed germins and GLPs are involved in diverse processes such as embryonic development and stress responses. The aim of this study was the analysis of barley germins and GLPs. In this study, 80 putative germins and GLPs have been identified in barley by using known 17 germins and GLP sequences. Analysis of germins and GLPs showed all germins and GLPs are distributed on all seven chromosomes that most of them spread through chromosome 3, 4 and 7 with 16, 18 and 12 proteins on each, respectively. The protein sizes varied between 185 and 335 amino acids, with an average length of 225 aa. Twelve conserved motifs were found. While germin motifs 1 and 3 were detected in all germins and GLPs, some motifs were found to be related to signalization. Interestingly, protein-protein interaction analysis demonstrated some GLPs are associated with RAB6-interacting golgin, oligopeptide transmembrane transporter activity, beta-glucuronidase activity, protein N-linked glycosylation, multi-pass membrane protein, and proteins containing zinc finger (Znf) domain and RING (really interesting new gene)-type zinc finger domains. Our findings suggest that barley germins and GLPs may have diverse functions that make them important candidates for crop improvement.

Enhanced thermo-tolerance in transgenic potato (Solanum tuberosum L.) overexpressing hydrogen peroxide-producing germin-like protein (GLP)

Germins and germin-like proteins (GLPs) were reported to participate in plant response to biotic and abiotic stresses involving hydrogen peroxide (H₂O₂) production, but their role in mitigating heat stress is poorly understood. Here, we investigated the ability of a Solanum tuberosum L. GLP (StGLP) gene isolated from the yeast cDNA library generated from heat-stressed potato plants and characterized its role in generating innate and/or acquired thermo-tolerance to potato via genetic transformation. The transgenic plants exhibited enhanced tolerance to gradual heat stress (GHS) compared with sudden heat shock (SHS) in terms of maximal cell viability, minimal ion leakage and reduced chlorophyll breakdown. Further, three StGLP transgenic lines (G9, G12 and G15) exhibited enhanced production of H₂O₂, which was either reduced or blocked by inhibitors of H₂O₂ under normal and heat stress conditions. This tolerance was mediated by up-regulation of antioxidant enzymes (catalase, ascorbate peroxidase and glutathione reductase) and other heat stress-responsive genes (StHSP70, StHSP20 and StHSP90) in transgenic potato plants. These results demonstrate that H₂O₂ produced by over-expression of StGLP in transgenic potato plants triggered the reactive oxygen species (ROS) scavenging signaling pathways controlling antioxidant and heat stress-responsive genes in these plants imparting tolerance to heat stress.

The rice germin-like protein OsGLP1 participates in acclimation to UV-B radiation

Exposure to ultraviolet B radiation (UV-B) stress can have serious effects on the growth and development of plants. Germin-like proteins (GLPs) may be involved in different abiotic and biotic stress responses in different plants, but little is known about the role of GLPs in UV-B stress response and acclimation in plants. In the present study, knockout of GLP 8-14 (OsGLP1) using the CRISPR/Cas9 system resulted in mutant rice (Oryza sativa L.) plants (herein called glp1) that exhibited UV-B-dependent formation of lesion mimic in leaves. Moreover, glp1 grown under solar radiation (including UV-B) showed decreased plant height and increased leaf angle, but we observed no significant differences in phenotypes between wild-type (WT) plants and glp1 grown under artificial light lacking UV-B. Fv/Fm, Y (II) and the expression of many genes, based on RNA-seq analysis, related to photosynthesis were also only reduced in glp1, but not in WT, after transfer from a growth cabinet illuminated with artificial white light lacking UV-B to growth under natural sunlight. The genes-associated with flavonoid metabolism as well as UV resistance locus 8 (OsUVR8), phytochrome interacting factor-like 15-like (OsPIF3), pyridoxal 5'-phosphate synthase subunit PDX1.2 (OsPDX1.2), deoxyribodipyrimidine photolyase (OsPHR), and deoxyribodipyrimidine photolyase family protein-like (OsPHRL) exhibited lower expression levels, while higher expression levels of mitogen-activated protein kinase 5-like (OsMPK3), mitogen-activated protein kinase 13-like (OsMPK13), and transcription factor MYB4-like (OsMYB4) were observed in glp1 than in WT after transfer from a growth cabinet illuminated with artificial white light to growth under natural sunlight. Therefore, mutations in OsGLP1 resulted in rice plants more sensitive to UV-B and reduced expression of some genes for UV-B protection, suggesting that OsGLP1 is involved in acclimation to UV-B radiation.

iTRAQ-Based Quantitative Proteomic Analysis of Chemically Induced Aquilaria sinensis Provides Insights into Agarwood Formation Mechanism

Agarwood is a precious traditional Chinese medicine with a variety of pharmacological effects. Although efforts have been made in elucidating the mechanism of agarwood formation, little progress is obtained till now. Therefore, the molecular mechanism of agarwood formation needs to be further explored using different biological approaches. In this study, the quantitative proteomic analysis using iTRAQ technology combined with transcriptomic and metabolomic analyses on chemically induced Aquilaria sinensis is performed to elucidate the agarwood formation mechanism by formic acid stimulus. Data are available via ProteomeXchange with identifier PXD007586; 1884 proteins are detected, 504 differential proteins that show at least twofold differences in their expression levels are selected based on GO annotations, KEGG, STRING analysis, and quantitative RT-PCR analysis. The results indicate that sesquiterpene synthase, germin-like protein, pathogenesis-related protein, 6-phosphogluconate dehydrogenase, lipoyl synthase, and superoxide dismutase play important roles in the agarwood formation, suggesting that the proteins related to the plant defensive response, the removal of peroxide, the disease-resistance, the biosythesis of glycan, fatty acids, and sesquiterpene are crucial for agarwood formation.

Identification and characterization of two germin-like proteins with oxalate oxidase activity from Calotropis procera latex

Germin-like proteins (GLPs) have been identified in several plant tissues. However, only one work describes GLP in latex fluids. Therefore, the goal of this study was to investigate GLPs in latex and get new insights concerning the structural and functional aspects of these proteins. Two complete sequences with high identity (>50%) with other GLPs, termed CpGLP1 and CpGLP2, were obtained and consecutively presented 216 and 206 amino acid residues, corresponding to molecular masses of 22.7 and 21.7kDa, pI 6.8 and 6.5. The three-dimensional models revealed overall folding similar to those reported for other plant GLPs. Both deduced sequences were grouped into the GER 2 subfamily. Molecular docking studies indicated a putative binding site consisting of three highly conserved histidines and a glutamate residue, which interacted with oxalate. This interaction was later supported by enzymatic assays. Superoxide dismutase (common activity in GLPs) was not detected for CpGLP1 and CpGLP2 by zymogram. The two proteins were detected in the latex, but not in non-germinated or germinated seeds and calli. These results give additional support that germin-like proteins are broadly distributed in plants and they are tissue-specific. This particularity deserves further studies to better understand their functions in latex.

Reactive oxygen species, essential molecules, during plant-pathogen interactions

Reactive oxygen species (ROS) are continually generated as a consequence of the normal metabolism in aerobic organisms. Accumulation and release of ROS into cell take place in response to a wide variety of adverse environmental conditions including salt, temperature, cold stresses and pathogen attack, among others. In plants, peroxidases class III, NADPH oxidase (NOX) locates in cell wall and plasma membrane, respectively, may be mainly enzymatic systems involving ROS generation. It is well documented that ROS play a dual role into cells, acting as important signal transduction molecules and as toxic molecules with strong oxidant power, however some aspects related to its function during plant-pathogen interactions remain unclear. This review focuses on the principal enzymatic systems involving ROS generation addressing the role of ROS as signal molecules during plant-pathogen interactions. We described how the chloroplasts, mitochondria and peroxisomes perceive the external stimuli as pathogen invasion, and trigger resistance response using ROS as signal molecule.

Proteomic analysis and purification of an unusual germin-like protein with proteolytic activity in the latex of Thevetia peruviana

The latex from Thevetia peruviana is rich in plant defense proteins, including a 120 kDa cysteine peptidase with structural characteristics similar to germin-like proteins. More than 20,000 plant species produce latex, including Apocynaceae, Sapotaceae, Papaveraceae and Euphorbiaceae. To better understand the physiological role played by latex fluids, a proteomic analysis of Thevetia peruviana (Pers.) Schum latex was performed using two-dimensional gel electrophoresis and mass spectrometry. A total of 33 proteins (86 %) were identified, including storage proteins, a peptidase inhibitor, cysteine peptidases, peroxidases and osmotins. An unusual cysteine peptidase, termed peruvianin-I, was purified from the latex by a single chromatographic step involving gel filtration. The enzyme (glycoprotein) was inhibited by E-64 and iodoacetamide and exhibited high specific activity towards azocasein (K m 17.6 µM), with an optimal pH and temperature of 5.0-6.0 and 25-37 °C, respectively. Gel filtration chromatography, two-dimensional gel electrophoresis, and mass spectrometry revealed that peruvianin-I possesses 120 kDa, pI 4.0, and six subunits (20 kDa). A unique N-terminal amino acid sequence was obtained to oligomer and monomers of peruvianin-I (1ADPGPLQDFCLADLNSPLFINGYPCRNPALAISDDF36). High-resolution images from atomic force microscopy showed the homohexameric structure of peruvianin-I may be organized as a trimer of dimers that form a central channel similar to germin-like proteins. Peruvianin-I exhibited no oxalate oxidase and superoxide dismutase activity or antifungal effects. Peruvianin-I represents the first germin-like protein (GLP) with cysteine peptidase activity, an activity unknown in the GLP family so far.

In vitro and in vivo evidence for oxalate oxidase activity of a germin-like protein from azalea

Germins and germin-like proteins (GLPs) comprise large families of extracellular plant glycoproteins that are structurally similar, yet they have been reported to have distinct biochemical activities: oxalate oxidase and superoxide dismutase activities, respectively. We expressed an azalea GLP (RmGLP2) in cultured cells of tobacco, and determined that the extracellular protein fraction and the recombinant RmGLP2 protein purified from these cells catalyzed the oxidation of oxalate. Notably, this activity is purportedly restricted to germin and has not been demonstrated for a GLP. Although the specific activity of the purified RmGLP2 protein was low compared with that of a previously characterized barley germin/oxalate oxidase, tobacco cells expressing RmGLP2 exhibited significantly reduced oxalate levels. Thus, RmGLP2 represents the first reported GLP with oxalate oxidase activity.

Developmental stimuli and stress factors affect expression of ClGLP1, an emerging allergen-related gene in Citrus limon

Germins and germin-like proteins (GLPs) constitute an ubiquitous family of plant proteins that seem to be involved in many developmental and stress related processes. A novel GLP cDNA was isolated from Citrus limon and structural features and genomic organization were investigated by in silico and Southern blots analysis. In lemon, the ClGLP1 encodes a 24.38 kDa which possesses a conserved motif of plant GLPs proteins. A phylogetic analysis mapped ClGLP1 as belonging to the GER3 subfamily into the GLP1 group of large GLP family. ClGLP1 was differentially expressed in the various organs and was highest in mature fruit. Moreover, expression in the fruit was tissue- and stage-related as well as dependent on agricultural practice (organic vs conventional). ClGLP1 transcripts increased during the transition from the green (180 days after blooming) to the yellow (240 days after blooming) mature fruit and were strongly enhanced in yellow mature fruit from organic compared with conventional culture. A sudden and systemic increase in ClGLP1 expression level was observed in leaves injured by wounding, together with an increase of endogenous H2O2 amount. Notably, an enhancement of H202 was observed in fruit peel during transition from green to yellow fruit stage. All together our data showed that ClGLP1 expression can be modulated in relation to both developmental stimuli and culture practices; evidence is also provided that through an oxidase activity this gene could play a role in fruit maturation as well as in stress responses.

Characterization of peanut germin-like proteins, AhGLPs in plant development and defense

Background

Germin-like superfamily members are ubiquitously expressed in various plant species and play important roles in plant development and defense. Although several GLPs have been identified in peanut (Arachis hypogaea L.), their roles in development and defense remain unknown. In this research, we study the spatiotemporal expression of AhGLPs in peanut and their functions in plant defense.

Results

We have identified three new AhGLP members (AhGLP3b, AhGLP5b and AhGLP7b) that have distinct but very closely related DNA sequences. The spatial and temporal expression profiles revealed that each peanut GLP gene has its distinct expression pattern in various tissues and developmental stages. This suggests that these genes all have their distinct roles in peanut development. Subcellular location analysis demonstrated that AhGLP2 and 5 undergo a protein transport process after synthesis. The expression of all AhGLPs increased in responding to Aspergillus flavus infection, suggesting AhGLPs' ubiquitous roles in defense to A. flavus. Each AhGLP gene had its unique response to various abiotic stresses (including salt, H₂O₂ stress and wound), biotic stresses (including leaf spot, mosaic and rust) and plant hormone stimulations (including SA and ABA treatments). These results indicate that AhGLPs have their distinct roles in plant defense. Moreover, in vivo study of AhGLP transgenic Arabidopsis showed that both AhGLP2 and 3 had salt tolerance, which made transgenic Arabidopsis grow well under 100 mM NaCl stress.

Conclusions

For the first time, our study analyzes the AhGLP gene expression profiles in peanut and reveals their roles under various stresses. These results provide an insight into the developmental and defensive roles of GLP gene family in peanut.

Harvest index, a parameter conditioning responsiveness of wheat plants to elevated CO2

The expansion of the world's population requires the development of high production agriculture. For this purpose, it is essential to identify target points conditioning crop responsiveness to predicted [CO2]. The aim of this study was to determine the relevance of ear sink strength in leaf protein and metabolomic profiles and its implications in photosynthetic activity and yield of durum wheat plants exposed to elevated [CO2]. For this purpose, a genotype with high harvest index (HI) (Triticum durum var. Sula) and another with low HI (Triticum durum var. Blanqueta) were exposed to elevated [CO2] (700 µmol mol(-1) versus 400 µmol mol(-1) CO2) in CO2 greenhouses. The obtained data highlighted that elevated [CO2] only increased plant growth in the genotype with the largest HI; Sula. Gas exchange analyses revealed that although exposure to 700 µmol mol(-1) depleted Rubisco content, Sula was capable of increasing the light-saturated rate of CO2 assimilation (Asat) whereas, in Blanqueta, the carbohydrate imbalance induced the down-regulation of Asat. The specific depletion of Rubisco in both genotypes under elevated [CO2], together with the enhancement of other proteins in the Calvin cycle, revealed that there was a redistribution of N from Rubisco towards RuBP regeneration. Moreover, the down-regulation of N, NO3 (-), amino acid, and organic acid content, together with the depletion of proteins involved in amino acid synthesis that was detected in Blanqueta grown at 700 µmol mol(-1) CO2, revealed that inhibition of N assimilation was involved in the carbohydrate imbalance and consequently with the down-regulation of photosynthesis and growth in these plants.

Overexpression of Arabidopsis plasmodesmata germin-like proteins disrupts root growth and development

In plants, a population of non-cell-autonomous proteins (NCAPs), including numerous transcription factors, move cell to cell through plasmodesmata (PD). In many cases, the intercellular trafficking of these NCAPs is regulated by their interaction with specific PD components. To gain further insight into the functions of this NCAP pathway, coimmunoprecipitation experiments were performed on a tobacco (Nicotiana tabacum) plasmodesmal-enriched cell wall protein preparation using as bait the NCAP, pumpkin (Cucurbita maxima) PHLOEM PROTEIN16 (Cm-PP16). A Cm-PP16 interaction partner, Nt-PLASMODESMAL GERMIN-LIKE PROTEIN1 (Nt-PDGLP1) was identified and shown to be a PD-located component. Arabidopsis thaliana putative orthologs, PDGLP1 and PDGLP2, were identified; expression studies indicated that, postgermination, these proteins were preferentially expressed in the root system. The PDGLP1 signal peptide was shown to function in localization to the PD by a novel mechanism involving the endoplasmic reticulum-Golgi secretory pathway. Overexpression of various tagged versions altered root meristem function, leading to reduced primary root but enhanced lateral root growth. This effect on root growth was corrected with an inability of these chimeric proteins to form stable PD-localized complexes. PDGLP1 and PDGLP2 appear to be involved in regulating primary root growth by controlling phloem-mediated allocation of resources between the primary and lateral root meristems.

A germin-like protein gene (CchGLP) of Capsicum chinense Jacq. is induced during incompatible interactions and displays Mn-superoxide dismutase activity

A germin-like gene (CchGLP) cloned from geminivirus-resistant pepper (Capsicum chinense Jacq. Line BG-3821) was characterized and the enzymatic activity of the expressed protein analyzed. The predicted protein consists of 203 amino acids, similar to other germin-like proteins. A highly conserved cupin domain and typical germin boxes, one of them containing three histidines and one glutamate, are also present in CchGLP. A signal peptide was predicted in the first 18 N-terminal amino acids, as well as one putative N-glycosylation site from residues 44-47. CchGLP was expressed in E. coli and the recombinant protein displayed manganese superoxide dismutase (Mn-SOD) activity. Molecular analysis showed that CchGLP is present in one copy in the C. chinense Jacq. genome and was induced in plants by ethylene (Et) and salicylic acid (SA) but not jasmonic acid (JA) applications in the absence of pathogens. Meanwhile, incompatible interactions with either Pepper golden mosaic virus (PepGMV) or Pepper huasteco yellow vein virus (PHYVV) caused local and systemic CchGLP induction in these geminivirus-resistant plants, but not in a susceptible accession. Compatible interactions with PHYVV, PepGMV and oomycete Phytophthora capsici did not induce CchGLP expression. Thus, these results indicate that CchGLP encodes a Mn-SOD, which is induced in the C. chinense geminivirus-resistant line BG-3821, likely using SA and Et signaling pathways during incompatible interactions with geminiviruses PepGMV and PHYVV.

Comparative transcriptomics of drought responses in Populus: a meta-analysis of genome-wide expression profiling in mature leaves and root apices across two genotypes

Background

Comparative genomics has emerged as a promising means of unravelling the molecular networks underlying complex traits such as drought tolerance. Here we assess the genotype-dependent component of the drought-induced transcriptome response in two poplar genotypes differing in drought tolerance. Drought-induced responses were analysed in leaves and root apices and were compared with available transcriptome data from other Populus species.

Results

Using a multi-species designed microarray, a genomic DNA-based selection of probesets provided an unambiguous between-genotype comparison. Analyses of functional group enrichment enabled the extraction of processes physiologically relevant to drought response. The drought-driven changes in gene expression occurring in root apices were consistent across treatments and genotypes. For mature leaves, the transcriptome response varied weakly but in accordance with the duration of water deficit. A differential clustering algorithm revealed similar and divergent gene co-expression patterns among the two genotypes. Since moderate stress levels induced similar physiological responses in both genotypes, the genotype-dependent transcriptional responses could be considered as intrinsic divergences in genome functioning. Our meta-analysis detected several candidate genes and processes that are differentially regulated in root and leaf, potentially under developmental control, and preferentially involved in early and long-term responses to drought.

Conclusions

In poplar, the well-known drought-induced activation of sensing and signalling cascades was specific to the early response in leaves but was found to be general in root apices. Comparing our results to what is known in arabidopsis, we found that transcriptional remodelling included signalling and a response to energy deficit in roots in parallel with transcriptional indices of hampered assimilation in leaves, particularly in the drought-sensitive poplar genotype.

Identification and analysis of the germin-like gene family in soybean

BACKGROUND

Germin and germin-like proteins constitute a ubiquitous family of plant proteins. A role of some family members in defense against pathogen attack had been proposed based on gene regulation studies and transgenic approaches. Soybean (G. max L. Merr.) germin genes had not been characterized at the molecular and functional levels.

RESULTS

In the present study, twenty-one germin gene members in soybean cultivar 'Maple Arrow' (partial resistance to Sclerotinia stem rot of soybean) were identified by in silico identification and RACE method (GmGER 1 to GmGER 21). A genome-wide analyses of these germin-like protein genes using a bioinformatics approach showed that the genes located on chromosomes 8, 1, 15, 20, 16, 19, 7, 3 and 10, on which more disease-resistant genes were located on. Sequence comparison revealed that the genes encoded three germin-like domains. The phylogenetic relationships and functional diversity of the germin gene family of soybean were analyzed among diverse genera. The expression of the GmGER genes treated with exogenous IAA suggested that GmGER genes might be regulated by auxin. Transgenic tobacco that expressed the GmGER 15 [corrected] gene exhibited high tolerance to the salt stress. In addition, the GmGER mRNA increased transiently at darkness and peaked at a time that corresponded approximately to the critical night length. The mRNA did not accumulate significantly under the constant light condition, and did not change greatly under the SD and LD treatments.

CONCLUSIONS

This study provides a complex overview of the GmGER genes in soybean. Phylogenetic analysis suggested that the germin and germin-like genes of the plant species that had been founded might be evolved by independent gene duplication events. The experiment indicated that germin genes exhibited diverse expression patterns during soybean development. The different time courses of the mRNAs accumulation of GmGER genes in soybean leaves appeared to have a regular photoperiodic reaction in darkness. Also the GmGER genes were proved to response to abiotic stress (such as auxin and salt), suggesting that these paralogous genes were likely involved in complex biological processes in soybean.

Germin-like proteins (GLPs) in cereal genomes: gene clustering and dynamic roles in plant defence

The recent release of the genome sequences of a number of crop and model plant species has made it possible to define the genome organisation and functional characteristics of specific genes and gene families of agronomic importance. For instance, Sorghum bicolor, maize (Zea mays) and Brachypodium distachyon genome sequences along with the model grass species rice (Oryza sativa) enable the comparative analysis of genes involved in plant defence. Germin-like proteins (GLPs) are a small, functionally and taxonomically diverse class of cupin-domain containing proteins that have recently been shown to cluster in an area of rice chromosome 8. The genomic location of this gene cluster overlaps with a disease resistance QTL that provides defence against two rice fungal pathogens (Magnaporthe oryzae and Rhizoctonia solani). Studies showing the involvement of GLPs in basal host resistance against powdery mildew (Blumeria graminis ssp.) have also been reported in barley and wheat. In this mini-review, we compare the close proximity of GLPs in publicly available cereal crop genomes and discuss the contribution that these proteins, and their genome sequence organisation, play in plant defence.

Preparation and Characterization of 5′-Phosphodiesterase from Barley Malt Rootlets

Two 5′- phosphodiesterases (5′-PDE-a and 5′-PDE-b) were isolated from barley malt rootlets, and further purified by gel filtration on Sephadex G-25 and Sephadex G-75. 5′-PDE-a had a pH optimum of 5.0, temperature optimum of 70oC, and specific activity of 0.0143 mM ·mg−1-min−1. 5′-PDE –b had a pH optimum of 6.0, temperature optimum of 65°C and specific activity of 0.0125 mM ·mg−1·min−1. Both enzymes can be used to hydrolyze RNA to form 5′-nucleotides. The enzymes were quite stable at 70oC for 420 minutes. The Km was 0.24 mM for 5′-PDE-a and 0.16 mM for 5′-PDE-b with t-RNA (yeast) as substrate.

Diphosphonucleotide phosphatase/phosphodiesterase (PPD1) from yellow lupin (Lupinus luteus L.) contains an iron-manganese center

Yellow lupin diphosphonucleotide phosphatase/phosphodiesterase (PPD1) represents a novel group of enzymes. Here we report that it possesses one iron atom and one manganese atom (1:1 molar ratio) per subunit. The enzyme exhibits visible absorption maximum at approximately 530 nm. Prolonged oxidation of PPD1 leads to loss of the charge-transfer band and catalytic activity, whereas after reduction PPD1 remains active. Replacement of conserved amino-acid residues coordinating metals results in the loss of enzymatic activity. Despite low amino-acid sequence homology of PPD1 to well-characterized approximately 55-kDa purple acid phosphatases, their overall fold, topology of active center and metal content are highly similar.

Effects of beta-1,3-glucan from Septoria tritici on structural defence responses in wheat

The accumulation of the pathogenesis-related (PR) proteins beta-1,3-glucanase and chitinase and structural defence responses were studied in leaves of wheat either resistant or susceptible to the hemibiotrophic pathogen Septoria tritici. Resistance was associated with an early accumulation of beta-1,3-glucanase and chitinase transcripts followed by a subsequent reduction in level. Resistance was also associated with high activity of beta-1,3-glucanase, especially in the apoplastic fluid, in accordance with the biotrophic/endophytic lifestyle of the pathogen in the apoplastic spaces, thus showing the highly localized accumulation of defence proteins in the vicinity of the pathogen. Isoform analysis of beta-1,3-glucanase from the apoplastic fluid revealed that resistance was associated with the accumulation of an endo-beta-1,3-glucanase, previously implicated in defence against pathogens, and a protein with identity to ADPG pyrophosphatase (92%) and germin-like proteins (93%), which may be involved in cell wall reinforcement. In accordance with this, glycoproteins like extensin were released into the apoplast and callose accumulated to a greater extent in cell walls, whereas lignin and polyphenolics were not found to correlate with defence. Treatment of a susceptible wheat cultivar with purified beta-1,3-glucan fragments from cell walls of S. tritici gave complete protection against disease and this was accompanied by increased gene expression of beta-1,3-glucanase and the deposition of callose. Collectively, these data indicate that resistance is dependent on a fast, initial recognition of the pathogen, probably due to beta-1,3-glucan in the fungal cell walls, and this results in the accumulation of beta-1,3-glucanase and structural defence responses, which may directly inhibit the pathogen and protect the host against fungal enzymes and toxins.

Induction of a grapevine germin-like protein (VvGLP3) gene is closely linked to the site of Erysiphe necator infection: a possible role in defense?

Germin-like proteins (GLP) have various proposed roles in plant development and defense. Seven novel GLP cDNA clones were isolated from grapevine (Vitis vinifera cv. Chardonnay). Reverse transcriptase-polymerase chain reaction expression analysis revealed that the VvGLP genes exhibit diverse and highly specific patterns of expression in response to a variety of abiotic and biotic treatments, including challenge by Erysiphe necator, Plasmopara viticola, and Botrytis cinerea, suggesting a diversity of roles for each of the GLP family members. Significantly, one of the grapevine GLP genes, VvGLP3, is induced specifically by E. necator infection and expression is closely linked to the site of infection. Subcellular localization of VvGLP3 determined by transient expression of a VvGLP3:GFP fusion construct in onion cells indicated that the recombinant protein was targeted to the cell wall. Recombinant VvGLP3 was successfully expressed in Arabidopsis thaliana and the partially purified recombinant protein was demonstrated to have superoxide dismutase activity. This data has provided an insight into the diverse nature of the GLP family in grapevine and suggests that VvGLP3 may be involved in the defense response against E. necator.

Cloning and sequence analysis of germin-like protein gene 2 promoter from Oryza sativa L. ssp. indica

Germin and germin-like proteins (GLPs) are water soluble extracellular proteins reportedly expressed in response to some environmental and developmental signals. Some enzymatic activities have also been associated with germin/GLPs. However, their role in overall metabolism has not been fully understood. Significant insight into their function may also be gained by analysis of their promoter. During this study, about 1107 bp 5'region of OsRGLP2 gene was amplified, cloned and sequenced. The sequence analysis by BLAST showed that this promoter sequence has five common regions (CR1-CR5) of different sizes, which are repeated at 3-6 other locations in 30 kb region in which this gene driven by its promoter is located. Interestingly, all the genes driven by promoter harboring these common regions are GLPs/putative germins. Analysis of these common regions located on OsRGLP2 indicated presence of many elements including those for light responsiveness, dehydration and dark induced senescence, stresses (pathogen and salt), plant growth regulators, pollen specific expression and elements related to seed storage proteins. Analysis of the 30 kb germin/GLP clustered region by GenScan detected each gene to have a putative 40 bp promoter which contains TATA box and Dof factor which turned out to be a part of CR2.

Rice plastidial N-glycosylated nucleotide pyrophosphatase/phosphodiesterase is transported from the ER-golgi to the chloroplast through the secretory pathway

A nucleotide pyrophosphatase/phosphodiesterase (NPP) activity that catalyzes the hydrolytic breakdown of ADP-glucose (ADPG) has been shown to occur in the plastidial compartment of both mono- and dicotyledonous plants. To learn more about this enzyme, we purified two NPPs from rice (Oryza sativa) and barley (Hordeum vulgare) seedlings. Both enzymes are glycosylated, since they bind to concanavalin A, stain with periodic acid-Schiff reagent, and are digested by Endo-H. A complete rice NPP cDNA, designated as NPP1, was isolated, characterized, and overexpressed in transgenic plants displaying high ADPG hydrolytic activity. Databank searches revealed that NPP1 belongs to a functionally divergent group of plant nucleotide hydrolases. NPP1 contains numerous N-glycosylation sites and a cleavable hydrophobic signal sequence that does not match with the N-terminal part of the mature protein. Both immunocytochemical analyses and confocal fluorescence microscopy of rice cells expressing NPP1 fused with green fluorescent protein (GFP) revealed that NPP1-GFP occurs in the plastidial compartment. Brefeldin A treatment of NPP1-GFP-expressing cells prevented NPP1-GFP accumulation in the chloroplasts. Endo-H digestibility studies revealed that both NPP1 and NPP1-GFP in the chloroplast are glycosylated. Collectively, these data demonstrate the trafficking of glycosylated proteins from the endoplasmic reticulum-Golgi system to the chloroplast in higher plants.

The multigene family encoding germin-like proteins of barley. Regulation and function in Basal host resistance

Germin-like proteins (GLPs) have been shown to be encoded by multigene families in several plant species and a role of some subfamily members in defense against pathogen attack has been proposed based on gene regulation studies and transgenic approaches. We studied the function of six GLP subfamilies of barley (Hordeum vulgare) by selecting single mRNAs for gene expression studies as well as overexpression and gene-silencing experiments in barley and Arabidopsis (Arabidopsis thaliana). Expression of all six subfamilies was high in very young seedlings, including roots. The expression pattern gradually changed from developmental to conditional with increasing plant age, whereby pathogen attack and exogenous hydrogen peroxide application were found to be the strongest signals for induction of several GLP subfamilies. Transcripts of four of five GLP subfamilies that are expressed in shoots were predominantly accumulating in the leaf epidermis. Transient overexpression of HvGER4 or HvGER5 as well as transient silencing by RNA interference of HvGER3 or HvGER5 protected barley epidermal cells from attack by the appropriate powdery mildew fungus Blumeria graminis f. sp. hordei. Silencing of HvGER4 induced hypersusceptibility. Transient and stable expression of subfamily members revealed HvGER5 as a new extracellular superoxide dismutase, and protection by overexpression could be demonstrated to be dependent on superoxide dismutase activity of the encoded protein. Data suggest a complex interplay of HvGER proteins in fine regulation of basal resistance against B. graminis.

Spatial and temporal divergence of expression in duplicated barley germin-like protein-encoding genes

Subfunctionalization is the process by which a pair of duplicated genes, or paralogs, experiences a reduction of individual expression patterns or function while still reproducing the complete expression pattern and function of the ancestral gene. Two germin-like protein (GLP)-encoding genes, GerB and GerF, are paralogs that belong to a small gene family in barley (Hordeum vulgare). Both genes share high nucleotide sequence similarity in coding and noncoding regions and encode identical apoplastic proteins. The use of RNA gel blots, coupled with single-stranded conformation polymorphism (SSCP) analysis of RT-PCR products, elucidated the developmental and tissue-specific expression patterns of each gene. Individual expression patterns provided evidence of both overlapping redundancy and early subfunctionalization. GerB is predominantly expressed in developing shoots, while GerF is predominantly expressed in seedling roots, developing spikes, and pericarp/testa. GerF promoter deletion studies located a region (-356/-97) responsible for high promoter activity and showed the ability of GerB and GerF upstream regions to drive gfp expression in coleoptiles, epicarps, and lemma/palea of developing spikes. The observed expression patterns are consistent with proposed roles in plant development and defense mechanisms for this gene family. These roles may explain why redundancy has been selectively maintained in this duplicate gene pair.

The phosphodiesterase activity of the HmsP EAL domain is required for negative regulation of biofilm formation in Yersinia pestis

In Yersinia pestis, biofilm formation is stimulated by HmsT, a GGDEF-domain containing protein that synthesizes cyclic-di-GMP (c-di-GMP), and inhibited by HmsP, an EAL-domain protein. Only the EAL-domain portion of HmsP is required to inhibit biofilm formation. The EAL domain of HmsP was purified as a 6XHis-tag fusion protein and demonstrated to have phosphodiesterase activity using bis(p-nitrophenyl) phosphate (bis-pNPP) as a substrate. This enzymatic activity was strictly manganese dependent. A critical residue (E506) of HmsP within the EAL domain, that is required for inhibition of biofilm formation, is also essential for this phosphodiesterase activity. While the proposed function of EAL-domain proteins is to linearize c-di-GMP, this is a direct demonstration of the required phosphodiesterase activity of a purified EAL-domain protein.

Cloning and expression analysis of Zmglp1, a new germin-like protein gene in maize

The cDNA and genomic DNA of a green tissue-specific gene were cloned from maize (Zea mays L.) using cDNA-amplified fragment length polymorphism (cDNA-AFLP) and library screening. The deduced protein was highly similar to Hordeum vulgare germin-like protein 1 (HvGLP1), and the maize gene was therefore designated Zmglp1. Northern blot specifically detected the mRNA of Zmglp1 in young whorl leaves at the early-whorl stage. However, at the late-whorl, tassel, and silk stages, Zmglp1 transcripts were highly abundant in young whorl leaves; less abundant in mature leaves, young tassels, and cobs; and not detectable in roots, immature kernels, and stalks. RNA in situ hybridization revealed that Zmglp1 expressed only in mesophyllous, phloem, and guard cells in the young whorl leaves. Deletion analysis of the promoter in transgenic Arabidopsis resulted in the identification of several regions containing important regulatory cis-elements controlling the expression levels and circadian rhythm-oscillated patterns of Zmglp1.

Germin-like protein gene family of a moss, Physcomitrella patens, phylogenetically falls into two characteristic new clades

We identified 77 EST clones encoding germin-like proteins (GLPs) from a moss, Physcomitrella patens in a database search. These Physcomitrella GLPs ( PpGLP s) were separated into seven groups based on DNA sequence homology. Phylogenetic analysis showed that these groups were divided into two novel clades clearly distinguishable from higher plant germins and GLPs, named bryophyte subfamilies 1 and 2. PpGLPs belonging to bryophyte subfamilies 1 lacked two cysteines at the conserved positions observed in higher plant germins or GLPs. PpGLPs belonging to bryophyte subfamily 2 contained two cysteines as observed in higher plant germins and GLPs. In bryophyte subfamily 1, 12 amino acids, in which one of two cysteines is included, were deleted between boxes A and B. Further, we determined the genomic structure of all of seven PpGLP genes. The sequences of PpGLP s of bryophyte subfamily 1 contained one or two introns, whereas those of bryophyte subfamily 2 contained no introns. Other GLPs from bryophytes, a liverwort GLP from Marchantia polymorpha , and two moss GLPs from Barbula unguiculata and Ceratodon purpureus also fell into bryophyte subfamily 1 and bryophyte subfamily 2, respectively. No higher plant germins and GLPs were grouped into the bryophyte subfamilies 1 and 2 by our analysis. Moreover, we revealed that PpGLP6 had manganese-containing extracellular superoxide dismutase activity. These results indicated that bryophyte possess characteristic GLPs, which phylogenetically are clearly distinguishable from higher plant GLPs.

Identification and characterization of plant glycerophosphodiester phosphodiesterase

GPX-PDE (glycerophosphodiester phosphodiesterase; EC 3.1.4.46) is a relatively poorly characterized enzyme that catalyses the hydrolysis of various glycerophosphodiesters (glycerophosphocholine, glycerophosphoethanolamine, glycerophosphoglycerol, glycerophosphoserine and bis-glycerophosphoglycerol), releasing sn-glycerol 3-phosphate and the corresponding alcohol. In a previous study, we demonstrated the existence of a novel GPX-PDE in the cell walls and vacuoles of plant cells. Since no GPX-PDE had been identified in any plant organism, the purification of GPX-PDE from carrot cell walls was attempted. After extraction of cell wall proteins from carrot cell suspension cultures with CaCl2, GPX-PDE was purified up to 2700-fold using, successively, ammonium sulphate precipitation, gel filtration and concanavalin A-Sepharose. Internal sequence analysis of a 55 kDa protein identified in the extract following 2700-fold purification revealed strong similarity to the primary sequence of GLPQ, a bacterial GPX-PDE. To confirm the identity of plant GPX-PDE, an Arabidopsis thaliana cDNA similar to that encoding the bacterial GPX-PDE was cloned and overexpressed in a bacterial expression system, and was used to raise antibodies against the putative Arabidopsis thaliana GPX-PDE. Immunochemical assays performed on carrot cell wall proteins extracted by CaCl2 treatment showed a strong correlation between GPX-PDE activity and detection of the 55 kDa protein, validating the identity of the plant GPX-PDE. Finally, various properties of the purified enzyme were investigated. GPX-PDE is a multimeric enzyme, specific for glycerophosphodiesters, exhibiting a K(m) of 36 microM for glycerophosphocholine and active within a wide pH range (from 4 to 10). Since these properties are similar to those of GLPQ, the bacterial GPX-PDE, the similarities between plant and bacterial enzymes are also discussed.

Most of ADP x glucose linked to starch biosynthesis occurs outside the chloroplast in source leaves

Sucrose and starch are end products of two segregated gluconeogenic pathways, and their production takes place in the cytosol and chloroplast of green leaves, respectively. According to this view, the plastidial ADP.glucose (ADPG) pyrophosphorylase (AGP) is the sole enzyme catalyzing the synthesis of the starch precursor molecule ADPG. However, a growing body of evidences indicates that starch formation involves the import of cytosolic ADPG to the chloroplast. This evidence is consistent with the idea that synthesis of the ADPG linked to starch biosynthesis takes place in the cytosol by means of sucrose synthase, whereas AGP channels the glucose units derived from the starch breakdown. To test this hypothesis, we first investigated the subcellular localization of ADPG. Toward this end, we constructed transgenic potato plants that expressed the ADPG-cleaving adenosine diphosphate sugar pyrophosphatase (ASPP) from Escherichia coli either in the chloroplast or in the cytosol. Source leaves from plants expressing ASPP in the chloroplast exhibited reduced starch and normal ADPG content as compared with control plants. Most importantly however, leaves from plants expressing ASPP in the cytosol showed a large reduction of the levels of both ADPG and starch, whereas hexose phosphates increased as compared with control plants. No pleiotropic changes in photosynthetic parameters and maximum catalytic activities of enzymes closely linked to starch and sucrose metabolism could be detected in the leaves expressing ASPP in the cytosol. The overall results show that, essentially similar to cereal endosperms, most of the ADPG linked to starch biosynthesis in source leaves occurs in the cytosol.

Tobacco nectarin V is a flavin-containing berberine bridge enzyme-like protein with glucose oxidase activity

Ornamental tobacco (Nicotiana langsdorffii X N. sanderae) secretes a limited array of proteins (nectarins) into its floral nectar. Careful sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of tobacco nectar revealed that a broad protein band from 61 to 65 kD actually consists of five discrete protein bands. N-terminal sequencing and tryptic peptide mass spectrometry fingerprint analysis demonstrated that the upper three bands are isoforms of the same protein, NEC5 (Nectarin V), whereas the lower two bands, NEC4 (Nectarin IV), are related to each other but not to NEC5. Reverse transcription-polymerase chain reaction (RT-PCR) based upon N-terminal sequence of NEC5 generated a short cDNA that encoded the N terminus of the NEC5 protein. Two rounds of inverse-PCR using genomic DNA permitted the isolation of approximately one-half of the coding region of the nec5 gene along with 787 nucleotides of the 5'-flanking region. This DNA fragment was used as a probe to isolate a near full-length nec5 clone from a nectary-derived cDNA library. BLAST analysis identified the nec5 cDNA as a berberine bridge enzyme-like protein. Approximately 40% of the cDNA sequence corresponded to peptides that were identified by tryptic peptide mass spectrometry fingerprint analysis of the NEC5 protein, thereby confirming that this cDNA encoded the NEC5 protein. In-gel assays also demonstrated that NEC5 contains a covalently linked flavin, and it possesses glucose oxidase activity. RT-PCR-based expression analyses showed that nec5 expression is limited exclusively to the nectary gland during late stages of floral development.

The germinlike protein GLP4 exhibits superoxide dismutase activity and is an important component of quantitative resistance in wheat and barley

Germinlike proteins (GLP) are encoded in plants by a gene family with proposed functions in plant development and defense. Genes of GLP subfamily 4 of barley (HvGLP4, formerly referred to as HvOxOLP) and the wheat orthologue TaGLP4 (formerly referred to as TaGLP2a) were previously found to be expressed in pathogen-attacked epidermal tissue of barley and wheat leaves, and the corresponding proteins are proposed to accumulate in the apoplast. Here, the role of HvGLP4 and TaGLP4 in the defense of barley and wheat against Blumeria graminis (DC.) E. O. Speer, the cereal powdery mildew fungus, was examined in an epidermal transient expression system and in transgenic Arabidopsis thaliana plants overexpressing His-tagged HvGLP4. Leaf extracts of transgenic Arabidopsis overexpressing HvGLP4 contained a novel His-tagged protein with superoxide dismutase activity and HvGLP4 epitopes. Transient overexpression of TaGLP4 and HvGLP4 enhanced resistance against B. graminis in wheat and barley, whereas transient silencing by RNA interference reduced basal resistance in both cereals. The effect of GLP4 overexpression or silencing was strongly influenced by the genotype of the plant. The data suggest that members of GLP subfamily 4 are components of quantitative resistance in both barley and wheat, acting together with other, as yet unknown, plant components.

Cloning of a pine germin-like protein (GLP) gene promoter and analysis of its activity in transgenic tobacco Bright Yellow 2 cells

Germins and germin-like proteins (GLPs) constitute a large and highly diverse family of ubiquitous plant cell wall proteins. These proteins seem to be involved in many developmental stages and stress-related processes, but their exact participation in these processes generally remains obscure. In Pinus caribaea Morelet, the PcGER1 gene is expressed uniquely in embryo tissues, and encodes a GLP ionically bound to the walls of pine embryo cells maintained in 2,4-D-containing medium. We have cloned a genomic fragment including the 1520 bp 5'-upstream promoter region of PcGER1. This sequence contains, in its 1200 bp distal part, several cis elements (e.g. SEF4, 60 kDa protein, ABA RE and Dof recognition sites) present in genes responding to hormones and/or expressed in embryo or seed tissues, or during germination. The PcGER1 promoter sequence was cloned upstream of the GUS (beta-glucuronidase) reporter gene and transferred to tobacco Bright Yellow 2 (BY-2) cells via Agrobacterium tumefaciens-mediated transformation. Promoter activity and growth performances of transgenic asynchronous cell suspensions were analysed in the presence or absence of 2,4-D and/or BA. Optimal growth, maximum cell-wall yield and PcGER1 promoter activity were observed in the presence of 2,4-D and BA at day 4, the end of the exponential growth phase where 70-75% cells have a 2C DNA content. Analysis of promoter activity during the cell cycle in an aphidicoline-synchronized culture suggested that the expression is maximum in G1 cells. We also showed that under optimal growth conditions, 5' promoter deletions decreased the activity of the reporter gene. We discuss the function of this gene with regards to cell growth. Accession number: The PcGER1 promoter sequence was submitted to the genbank database under the accession number AY077704.

Glycerophosphocholine metabolism in higher plant cells. Evidence of a new glyceryl-phosphodiester phosphodiesterase

Glycerophosphocholine (GroPCho) is a diester that accumulates in different physiological processes leading to phospholipid remodeling. However, very little is known about its metabolism in higher plant cells. (31)P-Nuclear magnetic resonance spectroscopy and biochemical analyses performed on carrot (Daucus carota) cells fed with GroPCho revealed the existence of an extracellular GroPCho phosphodiesterase. This enzymatic activity splits GroPCho into sn-glycerol-3-phosphate and free choline. In vivo, sn-glycerol-3-phosphate is further hydrolyzed into glycerol and inorganic phosphate by acid phosphatase. We visualized the incorporation and the compartmentation of choline and observed that the major choline pool was phosphorylated and accumulated in the cytosol, whereas a minor fraction was incorporated in the vacuole as free choline. Isolation of plasma membranes, culture medium, and cell wall proteins enabled us to localize this phosphodiesterase activity on the cell wall. We also report the existence of an intracellular glycerophosphodiesterase. This second activity is localized in the vacuole and hydrolyzes GroPCho in a similar fashion to the cell wall phosphodiesterase. Both extra- and intracellular phosphodiesterases are widespread among different plant species and are often enhanced during phosphate deprivation. Finally, competition experiments on the extracellular phosphodiesterase suggested a specificity for glycerophosphodiesters (apparent K(m) of 50 microM), which distinguishes it from other phosphodiesterases previously described in the literature.

Ring up the curtain on DING proteins

DING proteins have a characteristic DINGGG- or closely related N-terminal sequence. One is found in human synovial fluid, and may be associated with rheumatoid arthritis. Other examples have receptor or signalling roles in various human and animal cells, or are involved in biomineralisation, and several of them bind to phytochemicals. As plant DING proteins have recently been discovered, we hypothesise that the DING protein-phytochemical association may represent one aspect of a ubiquitous receptor-linked signalling system. Several microbial proteins related to DING proteins have phosphatase activity, which may relate to biomineralisation in eukaryotic systems. Plant DING proteins and their microbial relatives may elicit allergic responses leading to arthritic disease.

Diphosphonucleotide phosphatase/phosphodiesterase from yellow lupin (Lupinus luteus L.) belongs to a novel group of specific metallophosphatases

A cDNA encoding previously purified and characterized diphosphonucleotide phosphatase/phosphodiesterase (PPD1) from yellow lupin (Lupinus luteus L.) was identified. The ppd1 gene encodes a protein containing a cleavable signal sequence. A functional expression of PPD1 in Saccharomyces cerevisiae confirmed the proper gene identification. A gene homologous to ppd1, encoding a putative membrane protein (PPD2), as well as fragments of two other genes encoding PPD3 and PPD4 proteins were also isolated. Amino acids composing the putative active center of PPD1 and PPD2 are similar to those present in known purple acid phosphatases, which suggests that the reported genes might encode a novel group of specific metallophosphatases. RT-PCR revealed that the corresponding PPD1 mRNA accumulates in stems and leaves, and PPD2 mRNA in stems, leaves and seedlings.

Physical and genetic mapping of barley (Hordeum vulgare) germin-like cDNAs

Germin with oxalate oxidase and superoxide dismutase activity is a homohexamer of six manganese-containing interlocked beta-jellyroll monomers with extreme resistance to heat and proteolytic degradation [Woo, E.-J., Dunwell, J. M., Goodenough, P. W., Marvier, A. C. & Pickersill, R. W. (2000) Nat. Struct. Biol. 7, 1036-1038]. This structure is conserved in germin-like proteins (GLPs) with other enzymatic functions and characteristic for proteins deposited in plant cell walls in response to pathogen attack and abiotic stress. Comparative nucleotide and amino acid sequence analyses of 49,610 barley expressed sequence tags identified 124 germin and germin-like cDNAs, which distributed into five subfamilies designated HvGER-I to HvGER-V. Representative cDNAs for these subfamilies hybridized to 67 bacterial artificial chromosome (BAC) clones from a library containing 6.3 genomic equivalents. Twenty-six BAC clones hybridized to the subfamily IV probe and identified a gene-rich region including clone 418E1 of 96 kb encoding eight GLPs (i.e., 1 gene per 12 kb). This BAC clone lacked highly repeated sequences and mapped to the subtelomeric region of the long arm of chromosome 4(4H). Among the six genes of the contig expressed in leaves, one specifies a protein known to be associated with papilla formation in the epidermis upon powdery mildew infection. Three structural genes for oxalate oxidase are present in subfamily I and eight GLPs of various functions in the other subfamilies. These genes map at loci in chromosomes 1(7H), 2 (2H), 3(3H), 4(4H), and 7(5H). Some are present on a single BAC clone. The results are discussed in relation to cereal genome organization.

Evolution of functional diversity in the cupin superfamily

The cupin superfamily of proteins is among the most functionally diverse of any described to date. It was named on the basis of the conserved beta-barrel fold ('cupa' is the Latin term for a small barrel), and comprises both enzymatic and non-enzymatic members, which have either one or two cupin domains. Within the conserved tertiary structure, the variety of biochemical function is provided by minor variation of the residues in the active site and the identity of the bound metal ion. This review discusses the advantages of this particular scaffold and provides an evolutionary analysis of 18 different subclasses within the cupin superfamily.

Oxalate decarboxylase requires manganese and dioxygen for activity. Overexpression and characterization of Bacillus subtilis YvrK and YoaN

The Bacillus subtilis oxalate decarboxylase (EC ), YvrK, converts oxalate to formate and CO(2). YvrK and the related hypothetical proteins YoaN and YxaG from B. subtilis have been successfully overexpressed in Escherichia coli. Recombinant YvrK and YoaN were found to be soluble enzymes with oxalate decarboxylase activity only when expressed in the presence of manganese salts. No enzyme activity has yet been detected for YxaG, which was expressed as a soluble protein without the requirement for manganese salts. YvrK and YoaN were found to catalyze minor side reactions: oxalate oxidation to produce H(2)O(2); and oxalate-dependent, H(2)O(2)-independent dye oxidations. The oxalate decarboxylase activity of purified YvrK was O(2)-dependent. YvrK was found to contain between 0.86 and 1.14 atoms of manganese/subunit. EPR spectroscopy showed that the metal ion was predominantly but not exclusively in the Mn(II) oxidation state. The hyperfine coupling constant (A = 9.5 millitesla) of the main g = 2 signal was consistent with oxygen and nitrogen ligands with hexacoordinate geometry. The structure of YvrK was modeled on the basis of homology with oxalate oxidase, canavalin, and phaseolin, and its hexameric oligomerization was predicted by analogy with proglycinin and homogentisate 1,2-dioxygenase. Although YvrK possesses two potential active sites, only one could be fully occupied by manganese. The possibility that the C-terminal domain active site has no manganese bound and is buried in an intersubunit interface within the hexameric enzyme is discussed. A mechanism for oxalate decarboxylation is proposed, in which both Mn(II) and O(2) are cofactors that act together as a two-electron sink during catalysis.

Adenosine diphosphate sugar pyrophosphatase prevents glycogen biosynthesis in Escherichia coli

An adenosine diphosphate sugar pyrophosphatase (ASPPase, EC ) has been characterized by using Escherichia coli. This enzyme, whose activities in the cell are inversely correlated with the intracellular glycogen content and the glucose concentration in the culture medium, hydrolyzes ADP-glucose, the precursor molecule of glycogen biosynthesis. ASPPase was purified to apparent homogeneity (over 3,000-fold), and sequence analyses revealed that it is a member of the ubiquitously distributed group of nucleotide pyrophosphatases designated as "nudix" hydrolases. Insertional mutagenesis experiments leading to the inactivation of the ASPPase encoding gene, aspP, produced cells with marginally low enzymatic activities and higher glycogen content than wild-type bacteria. aspP was cloned into an expression vector and introduced into E. coli. Transformed cells were shown to contain a dramatically reduced amount of glycogen, as compared with the untransformed bacteria. No pleiotropic changes in the bacterial growth occurred in both the aspP-overexpressing and aspP-deficient strains. The overall results pinpoint the reaction catalyzed by ASPPase as a potential step of regulating glycogen biosynthesis in E. coli.