Inducible defense-related proteins have been described in many plant species upon infection with oomycetes, fungi, bacteria, or viruses, or insect attack. Several types of proteins are common and have been classified into 17 families of pathogenesis-related proteins (PRs). Others have so far been found to occur more specifically in some plant species. Most PRs and related proteins are induced through the action of the signaling compounds salicylic acid, jasmonic acid, or ethylene, and possess antimicrobial activities in vitro through hydrolytic activities on cell walls, contact toxicity, and perhaps an involvement in defense signaling. However, when expressed in transgenic plants, they reduce only a limited number of diseases, depending on the nature of the protein, plant species, and pathogen involved. As exemplified by the PR-1 proteins in Arabidopsis and rice, many homologous proteins belonging to the same family are regulated developmentally and may serve different functions in specific organs or tissues. Several defense-related proteins are induced during senescence, wounding or cold stress, and some possess antifreeze activity. Many defense-related proteins are present constitutively in floral tissues and a substantial number of PR-like proteins in pollen, fruits, and vegetables can provoke allergy in humans. The evolutionary conservation of similar defense-related proteins in monocots and dicots, but also their divergent occurrence in other conditions, suggest that these proteins serve essential functions in plant life, whether in defense or not.

/pdf/significance-of-inducible-defense-related-proteins-in-1xu2abfq16.pdf

Significance of Inducible Defense-related Proteins in Infected Plants

Recently a novel DNA virus (Torque Teno Virus (TTV) has been identified in Japan and shown to be associated with elevated aminotransferase s levels after transfusion. However the exact role of TTV in pathogenesis of liver disease is yet to be established. The purpose of this study was to determine the prevalence of TTV in thalassemic patients and its relationship with elevated alanine-aminotransfrase (ALT) and aspartateaminotransfrase (AST). This cross-sectional analysis study was conducted on 452 thallasemic patients. Serums were collected from all of the patients, first ALT and AST levels were determined. Then, after DNA extraction, TTV DNA was amplified and detected using semi-nested PCR, followed by gel electrophoresis. Demographic characteristics and clinical data were collected from each participant for statistical analysis. The findings showed that 160 of 452 (35.4%) samples had TTV DNA detected by PCR. From 160 TTV DNA positive, 98 (61.20%) were female and 62 (38.80%) of them were male (P=0.549). The mean ALT and AST values in TTV positive group were higher than in TTV negative group, and the difference was statistically significant (p<0.0001). The result showed that the prevalence of TTV in thalassemic patients in Jahrom is less than other studies in Iran and the mean ALT and AST values in TTV positive individuals were about 2 times more than in TTV negative individuals.

/pdf/molecular-prevalence-and-clinical-importance-of-torque-teno-2fi9z1ixeg.pdf

Molecular Prevalence and Clinical Importance of Torque Teno Virus Infection in Thalassemia Patients as High Risk Individuals

Flavonoids are small molecular secondary metabolites synthesized by plants with various biological activities. Due to their physical and biochemical properties, they are capable of participating in plants' interactions with other organisms (microorganisms, animals and other plants) and their reactions to environmental stresses. The majority of their functions result from their strong antioxidative properties. Although an increasing number of studies focus on the application of flavonoids in medicine or the food industry, their relevance for the plants themselves also deserves extensive investigations. This review summarizes the current knowledge on the functions of flavonoids in the physiology of plants and their relations with the environment.

Flavonoids as Important Molecules of Plant Interactions with the Environment

The chalcone synthase superfamily of type III polyketide synthases.

In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.

/pdf/in-posidonia-oceanica-cadmium-induces-changes-in-dna-3cu7uj83mr.pdf

In Posidonia oceanica cadmium induces changes in DNA methylation and chromatin patterning

A cDNA clone was isolated by differential hybridization from a library prepared from barley leaves inoculated with the fungus Blumeria graminis f.sp. hordei (Bgh). The open reading frame of the insert (designated HvCHS2) encoded a polypeptide with 72–79% identity to chalcone synthases (CHS) and 65–68% identity to stilbene synthases. Alignments of the amino acid sequence of HvCHS2 with the consensus sequence of naringenin-CHS (EC 2.3.1.74) reveals significant differences between HvCHS2 and naringenin-CHS. HvCHS2 transcripts accumulate strongly in barley leaves in response to inoculation with Bgh, whereas only insignificant accumulation of barley naringenin-CHS (CHS1) transcripts is seen upon the inoculation. The accumulation of HvCHS2 transcripts is also elicited by UV light. To compare the activity of HvCHS2 with the activity of CHS1, the two enzymes were expressed in Escherichia coli. Both HvCHS2 and CHS1 catalyse the formation of chalcones. However, HvCHS2 and CHS1 differ in their substrate requirements. CHS1 uses cinnamoyl-CoA and 4-coumaroyl-CoA at comparable rates whereas feruloyl-CoA is a poor substrate for this enzyme. In contrast, HvCHS2 converts feruloyl-CoA and caffeoyl-CoA at the highest rate whereas cinnamoyl-CoA is a poor substrate. Thus, HvCHS2 is a novel pathogen and UV light induces homoeriodictyol/eriodictyol CHS involved in the direct production of flavonoids possessing multi-substituted B-rings.

A chalcone synthase with an unusual substrate preference is expressed in barley leaves in response to UV light and pathogen attack

We have shown previously that transcripts corresponding to the cDNA clone pBH72-F1, with similarities to O-methyltransferases (OMT), accumulated in barley leaves in response to attack by the pathogenic fungus Blumeria graminis (Plant Mol Biol 26 (1994) 1797) To investigate the accumulation pattern in the defence response and the organ localization of the pBH72-F1-encoded polypeptide (F1-OMT), an antiserum was raised against Escherichia coli expressed F1-OMT The 43 kDa protein was absent in normal leaves but accumulated strongly in response to pathogen attack The F1-OMT protein accumulated faster in barley lines inoculated with an avirulent B graminis isolates compared to a virulent isolate Additionally, F1-OMT related proteins were detected in developing kernels F1-OMT was expressed as a functional enzyme in E coli and the substrate specificity was investigated The enzyme exhibited OMT activity towards flavonoid aglycones with the highest activity against apigenin (4',5,7-trihydroxyflavone) In contrast, caffeic acid did not serve as substrate for F1-OMT The product of F1-OMT was analyzed by HPLC and GC-MS and found to be genkwanin (4',5-dihydroxy-7-methoxyflavone) Initial velocity data were best represented by a sequential bi-bi mechanism, and kinetic parameters of KSAM = 109 microM, Kapigenin = 46 microM and a specific activity of 045 mukat/g were obtained Barley F1-OMT, apigenin 7-O-methyltransferase, is suggested to be involved in the production of a methylated flavonoid phytoalexin

A flavonoid 7-O-methyltransferase is expressed in barley leaves in response to pathogen attack

14-3-3 proteins form a family of highly conserved proteins with central roles in many eukaryotic signalling networks. In plants, they bind to and activate the plasma membrane H+-ATPase, creating a binding site for the phytotoxin fusicoccin. Barley 14-3-3 transcripts accumulate in the epidermis upon inoculation with the powdery mildew fungus. We have isolated a cDNA encoding a plasma membrane H+-ATPase (HvHAI), which is also induced by powdery mildew attack. The C-terminal domain of this H+-ATPase interacts with 14-3-3 proteins in the yeast two-hybrid system. Inoculation with the powdery mildew fungus, or treatment with fusicoccin, results in an increase in fusicoccin binding ability of barley leaf membranes. Overlay assays show a fungus-induced increase in binding of digoxygenin-labelled 14-3-3 protein to several proteins including a 100 kDa membrane protein, probably the plasma membrane H+-ATPase. These effects are seen specifically in the inoculated epidermis and not in the whole leaf. We propose that 14-3-3 proteins are involved in an epidermis-specific response to the powdery mildew fungus, possibly via an activation of the plasma membrane H+-ATPase.

Do 14-3-3 proteins and plasma membrane H + -ATPases interact in the barley epidermis in response to the barley powdery mildew fungus?

A cDNA clone, pBH72-F1 (F1), was isolated from a cDNA library prepared from barley leaves 72 h after inoculation with Erysiphe graminis f.sp. hordei. The 1388 bp nucleotide sequence of pBH72-F1 contains an open reading frame encoding a 42.3 kDa polypeptide of 390 amino acids which shows sequence similarity to O-methyltransferases (OMTs) from different plant species; the highest identity (41%) was observed with a putative OMT expressed in roots of maize. A phylogenetic analysis shows that the barley and maize sequences are distinctly different from the ortho-diphenol-OMTs involved in lignin formation. A putative S-adenosyl-L-methionine-binding motif (KELVDDSITN) determined for a rabbit protein-carboxyl OMT is partially conserved in the encoded amino acid sequence. Genomic Southern blot hybridization shows that pBH72-F1 probably represents a single copy gene. The F1 clone corresponds to a gene transcript exhibiting a relatively late accumulation in mildew-infected barley leaves compared to other pathogen-induced transcripts, such as transcripts encoding PR proteins, a peroxidase, and transcripts homologous to a maize caffeic acid OMT. No transcript was detected in plants exhibiting papilla resistance at time points when resistance is thought to be manifested. The atypical transcript accumulation pattern for F1 was also observed after infection by other pathogens and after UV-light treatment.

A putative O-methyltransferase from barley is induced by fungal pathogens and UV light

Summary Two barley (Hordeum vulgare L.) cDNA clones (pBH6-12 and pBH6-17) were isolated from a cDNA library prepared from leaves 6 h after inoculation with Blumeria graminis f.sp. hordei (Bgh). The two transcripts accumulate strongly in response to Bgh, peaking around 6, 15-24 and 48-96 h after inoculation, concomitant with fungal penetration attempts, hypersensitive response and fungal growth. The encoded proteins, HvPR-17a and HvPR-17b, belong to a new family of plant pathogenesis-related proteins, designated 'PR-17'. The family also include NtPRp27 from tobacco (Okushima et al., 2000, Plant Mol. Biol.42, 479-488) and WCI-5 from wheat (Gorlach et al., 1996, Plant Cell8, 629-643), responsive to viral and fungal infection, respectively. Antisera were raised to HvPR-17a and HvPR-17b, and the proteins exhibit apparent molecular weights of 26 and 24 kDa, respectively. They accumulate in the mesophyll apoplast following Bgh-inoculation, as well as in the leaf epidermis, the only tissue to be invaded by the fungus. Several homologous plant proteins exist, and a highly conserved part of the members of this new protein family show similarity to the active site and to the peptide-binding groove of the exopeptidase 'aminopeptidase N' from eukaryotes and the endopeptidase 'thermolysin' from bacteria.

The molecular characterization of two barley proteins establishes the novel PR-17 family of pathogenesis-related proteins.

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