Infected Epidermal Cells Research Articles

Golovinomyces cichoracearum effector-associated nuclear localization of RPW8.2 amplifies its expression to boost immunity in Arabidopsis.

Arabidopsis RESISTANCE TO POWDERY MILDEW 8.2 (RPW8.2) is specifically induced by the powdery mildew (PM) fungus (Golovinomyces cichoracearum) in the infected epidermal cells to activate immunity. However, the mechanism of RPW8.2-induction is not well understood. Here, we identify a G. cichoracearum effector that interacts with RPW8.2, named Gc-RPW8.2 interacting protein 1 (GcR8IP1), by a yeast two-hybrid screen of an Arabidopsis cDNA library. GcR8IP1 is physically associated with RPW8.2 with its REALLY INTERESTING NEW GENE finger domain that is essential and sufficient for the association. GcR8IP1 was secreted and translocated into the nucleus of host cell infected with PM. Association of GcR8IP1 with RPW8.2 led to an increase in RPW8.2 in the nucleus. In turn, the nucleus-localized RPW8.2 promoted the activity of the RPW8.2 promoter, resulting in transcriptional self-amplification of RPW8.2 to boost immunity at infection sites. Additionally, ectopic expression or host-induced gene silencing of GcR8IP1 supported its role as a virulence factor in PM. Altogether, our results reveal a mechanism of RPW8.2-dependent defense strengthening via altered partitioning of RPW8.2 and transcriptional self-amplification triggered by a PM fungal effector, which exemplifies an atypical form of effector-triggered immunity.

Microscope studies of symptomless growth of Botrytis cinerea in Lactuca sativa and Arabidopsis thaliana.

The grey mould pathogen Botrytis cinerea forms systemic associations in some hosts, spreading into plant organs produced a considerable time after initial infection. These infections may have no macroscopic symptoms during much of the hosts' lifetime and are at least partially within the host tissue. The aim of the studies reported here was to locate and visualize these infections at a cellular level in Lactuca sativa (lettuce) and Arabidopsis thaliana. Symptomless but infected plants were produced by dry spore inoculation of plants growing in conditions previously shown to result in fungal spread from the initial inoculation site to newly developing plant organs. Tissue taken from inoculated plants was examined using confocal laser scanning microscopy. Two B. cinerea isolates were used: B05.10 and its GFP-labelled derivative Bcgfp1-3. Spore germination on leaf surfaces was followed by development of subcuticular inclusions and plant cell damage in single infected epidermal cells and sometimes a few nearby cells. Sparsely branched long hyphae arose and spread from the inclusions, mostly on the outer surface of the epidermal layer but occasionally below the cuticle or epidermal cells, where further inclusions formed. This was consistent with the pattern in time of recovery of B. cinerea from surface-sterilized leaf tissue. In the late symptomless phase, mycelium arising from internal fungal inclusions formed mycelial networks on the surface of leaves. Symptomless exterior mycelium grew on the roots in A. thaliana.

Subcuticular−Intracellular Hemibiotrophy of Colletotrichum lupini in Lupinus mutabilis

Anthracnose caused by Colletotrichum lupini is the most important disease affecting lupin cultivation worldwide. Lupinus mutabilis has been widely studied due to its high protein and oil content. However, it has proved to be sensitive to anthracnose, which limits the expansion of its cultivation. In this work, we seek to unveil the strategy that is used by C. lupini to infect and colonize L. mutabilis tissues using light and transmission electron microscopy (TEM). On petioles, pathogen penetration occurred from melanized appressoria, subcuticular intramural hyphae were seen 2 days after inoculation (dai), and the adjacent host cells remained intact. The switch to necrotrophy was observed 3 dai. At this time, the hyphae extended their colonization to the epidermal, cortex, and vascular cells. Wall degradation was more evident in the epidermal cells. TEM observations also revealed a loss of plasma membrane integrity and different levels of cytoplasm disorganization in the infected epidermal cells and in those of the first layers of the cortex. The disintegration of organelles occurred and was particularly visible in the chloroplasts. The necrotrophic phase culminated with the development of acervuli 6 dai. C. lupini used the same infection strategy on stems, but there was a delay in the penetration of host tissues and the appearance of the first symptoms.

Rolling circle amplification of begomoviral DNA from a single nucleus isolated by laser dissection microscopy

Laser dissection microscopy (LDM) is a method for isolating organelles, a specific cell or cells/tissue of interest from microscopic regions with the help of a laser. Here we describe a LDM-based isolation of begomovirus infected Nicotiana benthamiana epidermal cells and nuclei, in combination with a fast method to prepare non-fixed leaf epidermal samples for LDM. The bipartite Abutilon mosaic virus (AbMV) was used in which the coat protein gene of DNA A was deleted and replaced by the open reading frame (ORF) coding for the green fluorescent protein (GFP, accession: U87624), agro-infiltrated together with DNA B, to visualize infected cells. GFP expressing epidermal cells or nuclei were isolated by LDM with the MMi Cellcut system and viral circular DNA was amplified by rolling circle amplification (RCA). Subsequently, the RCA product was incubated with the restriction enzymes BamHI and PstI and restriction fragments were separated on an agarose gel to prove presence of the viral genome. It was shown that even a single-isolated nucleus harbored enough material to produce a sufficient restriction fragment pattern to identify a begomovirus infected cell/nucleus.

Serum Levels of Interleukin 17 in Patients with Human Papilloma Virus Infection

Warts (verrucas) are an extremely common, benign, and usually self-limited skin disease. Infection of epidermal cells with the human papillomavirus (HPV) results in cell proliferation and a thickened, warty papule on the skin. The aim of this study was to evaluate serum levels of Interleukin 17 in patients with verrucas,correlate their levels with different demographic and clinical data. Method: This present study included: patient group(1) included 30 verruca patients. In addition,15apparently healthy, age and sex matched individuals included as a control group (Group 2). All patients were selected from outpatient clinic of Dermatology ans Andrology department of Benha University Hospital from Jan 2020 t0 July 2020. Informed consents were obtained from all participants. The study was approved by the local ethics committee on research involving human subjects, Faculty of Medicine , Benha University. Results and conclusion: it is concluded that IL 17 levels are lower in verruca patients than controls.

Effects of the cucumber mosaic virus 2a protein on aphid-plant interactions in Arabidopsis thaliana.

The cucumber mosaic virus (CMV) 2a RNA‐dependent RNA polymerase protein has an additional function in Arabidopsis thaliana, which is to stimulate feeding deterrence (antixenosis) against aphids. Antixenosis is thought to increase the probability that aphids, after acquiring CMV particles from brief probes of an infected plant's epidermal cells, will be discouraged from settling and instead will spread inoculum to neighbouring plants. The amino acid sequences of 2a proteins encoded by a CMV strain that induces antixenosis in A. thaliana (Fny‐CMV) and one that does not (LS‐CMV) were compared to identify residues that might determine the triggering of antixenosis. These data were used to design reassortant viruses comprising Fny‐CMV RNAs 1 and 3, and recombinant CMV RNA 2 molecules encoding chimeric 2a proteins containing sequences derived from LS‐CMV and Fny‐CMV. Antixenosis induction was detected by measuring the mean relative growth rate and fecundity of aphids (Myzus persicae) confined on infected and on mock‐inoculated plants. An amino acid sequence determining antixenosis induction by CMV was found to reside between 2a protein residues 200 and 300. Subsequent mutant analysis delineated this to residue 237. We conjecture that the Fny‐CMV 2a protein valine‐237 plays some role in 2a protein‐induced antixenosis.

The isoelectric point of proteins influences their translocation to the extrahaustorial matrix of the barley powdery mildew fungus.

Many biotrophic fungal plant pathogens develop feeding structures, haustoria, inside living plant cells, which are essential for their success. Extrahaustorial membranes (EHMs) surround haustoria and delimit the extrahaustorial matrices (EHMxs). Little is known about transport mechanisms across EHMs and what properties proteins and nutrients need in order to cross these membranes. To investigate this further, we expressed fluorescent proteins in the cytosol of infected barley leaf epidermal cells after particle bombardment and investigated properties that influenced their localisation in the powdery mildew EHMx. We showed that this translocation is favoured by a neutral isoelectric point (pI) between 6.0 and 8.4. However, for proteins larger than 50 kDa, pI alone does not explain their localisation, hinting towards a more complex interplay between pI, size, and sequence properties. We discuss the possibility that an EHM translocon is involved in protein uptake into the EHMx.

Dual and Opposing Roles of Xanthine Dehydrogenase in Defense-Associated Reactive Oxygen Species Metabolism in Arabidopsis.

While plants produce reactive oxygen species (ROS) for stress signaling and pathogen defense, they need to remove excessive ROS induced during stress responses in order to minimize oxidative damage. How can plants fine-tune this balance and meet such conflicting needs? Here, we show that XANTHINE DEHYDROGENASE1 (XDH1) in Arabidopsis thaliana appears to play spatially opposite roles to serve this purpose. Through a large-scale genetic screen, we identified three missense mutations in XDH1 that impair XDH1's enzymatic functions and consequently affect the powdery mildew resistance mediated by RESISTANCE TO POWDERY MILDEW8 (RPW8) in epidermal cells and formation of xanthine-enriched autofluorescent objects in mesophyll cells. Further analyses revealed that in leaf epidermal cells, XDH1 likely functions as an oxidase, along with the NADPH oxidases RbohD and RbohF, to generate superoxide, which is dismutated into H2O2 The resulting enrichment of H2O2 in the fungal haustorial complex within infected epidermal cells helps to constrain the haustorium, thereby contributing to RPW8-dependent and RPW8-independent powdery mildew resistance. By contrast, in leaf mesophyll cells, XDH1 carries out xanthine dehydrogenase activity to produce uric acid in local and systemic tissues to scavenge H2O2 from stressed chloroplasts, thereby protecting plants from stress-induced oxidative damage. Thus, XDH1 plays spatially specified dual and opposing roles in modulation of ROS metabolism during defense responses in Arabidopsis.

Histopathology of S. tanaceti infection in pyrethrum leaf lamina

The infection process and life cycle of S. tanaceti in leaf lamina of pyrethrum plants was investigated using histopathology. Conidia attached firmly to the leaf surface before the infection hyphae penetrated directly into the epidermal cells of the leaf without forming appressoria. The maximum germination of conidia on leaf surface was 85 % at 54 HAI. Infection hyphae infected the epidermal and palisade parenchyma cells through the middle lamella. Brown lesions on the leaf were a result of infected necrotic epidermal cells. Extensive colonization through both intra- and intercellular hyphae along with pycnidia formation caused enormous damage to the infected cells at 12 DAI. Unlike the quadruple stain, both single and dual stains had very limited ability to visualise infection structures. These results have provided a better understanding of the physical interaction between the pathogen and the pyrethrum leaf tissues and will help to elucidate the complete disease cycle of S. tanaceti on pyrethrum plant.

LB1.5 Initial interactions of herpes simplex virus with human skin dendritic cells

Introduction The mechanism by which immunity to herpes simplex virus (HSV) is initiated is not completely defined. HSV initially infects the stratified squamous epithelium of the anogenital mucosa prior to entering nerve endings. We have recently reported that topical application of HSV-1 to human foreskin explants results in infection of epidermal Langerhans cells (LCs) which then emigrate into the dermis where they expressed the maturation marker CD80 and formed large cell clusters with BDCA3+ subsets of DC-SIGN+ and dermal dendritic cells (DCs) and. HSV-expressing LC fragments were observed inside the dermal DCs/macrophages. No other infected epidermal cells interacted with the dermal DCs (Kim et al. Plos Pathogens, 2015). Methods Therefore, we isolated LCs and dermal DCs from large abdominal skin specimens by collagenase digestion and flow sorting. LCs were pulsed with fluorescent tagged HSV and co-cultured with a subset of (BDCA3+) dermal DCs. Results All infected LCs showed markers of apoptosis at 18 hr p.i. Approximately 50% of BDCA3+ DCs co-localised with infected LCs and in some cases fragments of infected LCs were observed within the dermal DC cytoplasm. Such colocalizaton of HSV antigen bearing LCs and dermal DC subsets, was also detected within biopsies of initial genital herpes lesions. The mechanism of interaction of apoptotic LCs and dermal DCs, and uptake by phagocytosis are being determined. Conclusion Thus, a viral antigen relay takes place where HSV infected LCs slowly die by apoptosis during migration to the dermis and are taken up by dermal DCs by phagocytosis for subsequent antigen presentation. This provides a rationale for targeting these dermal DCs for mucosal or perhaps intradermal HSV immunisation. Disclosure of interest statement No pharmaceutical grants were received in the development of this study.

Exploring mechanisms of Interleukin-1α release from HSV-1 infected keratinocytes during active skin infection (INM6P.340)

Abstract IL-1 cytokines, IL-1α and IL-1β, have been widely studied in a variety of disease models. These molecules are mostly known for their inflammatory properties; however, they have been shown to have pleiotropic effects under diverse circumstances and within different cell types. Recently, the herpes simplex virus-1 (HSV-1) was shown to inhibit IL-1β release during infection and consequently possibly blocking IL-1β dependent immune responses. We previously demonstrated that IL-1α is expressed and released from cells exposed to bacteria. Utilizing a mouse model of HSV-1 skin infection, we recently further showed that an intracellular store of preformed IL-1α is released from keratinocytes soon after infection, independent of inflammatory caspase activation. IL-1α signaling through its receptor, IL-1R1, was subsequently responsible for leukocyte recruitment to infected epidermal cells. This showed, for the first time, this cytokine’s ability to act as an alarmin during cutaneous viral infection. Consequently, IL-1R1 knockout mice had an increased mortality rate compared to wild type mice due to viral dissemination. Recent studies have aimed to evaluate mechanisms whereby IL-1α is released from infected keratinocytes and discover potential proteins involved. These experiments will help to elucidate the role of IL-1α during viral infection while furthering our understanding of IL-1 signaling mechanisms.

Relay of herpes simplex virus between Langerhans cells and dermal dendritic cells in human skin.

The mechanism by which immunity to Herpes Simplex Virus (HSV) is initiated is not completely defined. HSV initially infects mucosal epidermis prior to entering nerve endings. In mice, epidermal Langerhans cells (LCs) are the first dendritic cells (DCs) to encounter HSV, but it is CD103+ dermal DCs that carry viral antigen to lymph nodes for antigen presentation, suggesting DC cross-talk in skin. In this study, we compared topically HSV-1 infected human foreskin explants with biopsies of initial human genital herpes lesions to show LCs are initially infected then emigrate into the dermis. Here, LCs bearing markers of maturation and apoptosis formed large cell clusters with BDCA3+ dermal DCs (thought to be equivalent to murine CD103+ dermal DCs) and DC-SIGN+ DCs/macrophages. HSV-expressing LC fragments were observed inside the dermal DCs/macrophages and the BDCA3+ dermal DCs had up-regulated a damaged cell uptake receptor CLEC9A. No other infected epidermal cells interacted with dermal DCs. Correspondingly, LCs isolated from human skin and infected with HSV-1 in vitro also underwent apoptosis and were taken up by similarly isolated BDCA3+ dermal DCs and DC-SIGN+ cells. Thus, we conclude a viral antigen relay takes place where HSV infected LCs undergo apoptosis and are taken up by dermal DCs for subsequent antigen presentation. This provides a rationale for targeting these cells with mucosal or perhaps intradermal HSV immunization.

Differential Effects of Viral Coat Protein on Induction of Hypersensitive Response and Systemic Movement of Tobacco Mosaic Virus and Tobacco Mild Green Mosaic Virus in Nicotiana megalosiphon

Tobacco mosaic virus (TMV) and Tobacco mild green mosaic virus (TMGMV) are both known to induce hypersensitive response (HR) local lesions in Nicotiana megalosiphon, a hybrid plant from a cross between N. suaveolens and N. fragrans, but only TMV is capable of systemic movement. Therefore, the determinants of induction of hypersensitive response and systemic movement of TMV and TMGMV in N. megalosiphon were further analyzed. HR was shown to be independent of the temperature indicating that the resistance responses are different from N gene responses induced in tobacco (N. tabacum cv. Xanthi-nc.) to TMV. Comparison of lesion growth between wild-type and transgenic tobacco plants encoding salicylate hydroxylase (nahG) indicated that TMV spread similarly in N. megalosiphon and Xanthi-nc./nahG plants. In addition, exogenous application of SA did not prevent systemic movement of TMV. Coat protein-deficient TMV failed to induce HR and move systemically in N. megalosiphon indicating that CP is the inducer of HR and determinant for systemic movement. However, single epidermal cells expressing TMV-CP did not undergo cell death suggesting that formation of HR cell death requires viral movement out of the initially infected epidermal cells or the presence of intact virus particles. Furthermore, comparison of different TMV strains, including virus vector carrying the CP of TMGMV-U5 in place of TMV-CP, showed no differences in the induction of HR and timing of systemic virus movement suggesting that CP is not the determinant for differential invasion of TMV and TMGMV.

Distinct APC subtypes drive spatially segregated CD4+ and CD8+ T-cell effector activity during skin infection with HSV-1.

Efficient infection control requires potent T-cell responses at sites of pathogen replication. However, the regulation of T-cell effector function in situ remains poorly understood. Here, we show key differences in the regulation of effector activity between CD4+ and CD8+ T-cells during skin infection with HSV-1. IFN-γ-producing CD4+ T cells disseminated widely throughout the skin and draining lymph nodes (LN), clearly exceeding the epithelial distribution of infectious virus. By contrast, IFN-γ-producing CD8+ T cells were only found within the infected epidermal layer of the skin and associated hair follicles. Mechanistically, while various subsets of lymphoid- and skin-derived dendritic cells (DC) elicited IFN-γ production by CD4+ T cells, CD8+ T cells responded exclusively to infected epidermal cells directly presenting viral antigen. Notably, uninfected cross-presenting DCs from both skin and LNs failed to trigger IFN-γ production by CD8+ T-cells. Thus, we describe a previously unappreciated complexity in the regulation of CD4+ and CD8+ T-cell effector activity that is subset-specific, microanatomically distinct and involves largely non-overlapping types of antigen-presenting cells (APC).

Ectopic Expression of RESISTANCE TO POWDERY MILDEW8.1 Confers Resistance to Fungal and Oomycete Pathogens in Arabidopsis

Broad-spectrum disease resistance is a highly valuable trait in plant breeding and attracts special attention in research. The Arabidopsis gene locus RESISTANCE TO POWDERY MILDEW 8 (RPW8) contains two adjacent homologous genes, RPW8.1 and RPW8.2, and confers broad-spectrum resistance to powdery mildew. Remarkably, the RPW8.2 protein is specifically localized to the extrahaustorial membrane (EHM) encasing the feeding structure of powdery mildew whereby RPW8.2 activates haustorium-targeted defenses. Here, we show that ectopic expression of the yellow fluorescent protein (YFP)-tagged RPW8.1 from the native promoter leads to unique cell death lesions and enhances resistance to virulent fungal and oomycete pathogens that cause powdery mildew and downy mildew diseases, respectively. In powdery mildew-infected plants, RPW8.1-YFP accumulates at higher levels in the mesophyll cells underneath the infected epidermal cells where RPW8.2-YFP is mainly expressed. This cell type-preferential protein accumulation pattern largely correlates with that of H(2)O(2) accumulation, suggesting that RPW8.1 may spatially collaborate with RPW8.2 in activation of resistance to powdery mildew. Interestingly, when ectopically expressed from the RPW8.2 promoter, RPW8.1-YFP is also targeted to the EHM of powdery mildew and the transgenic plants display resistance to both powdery mildew and downy mildew. Using YFP as a reporter, we further reveal that the RPW8.1 promoter is constitutively active but induced to higher levels in cells at the infection site, whereas the RPW8.2 promoter is activated specifically in cells at the infection site. Taken together, our results suggest that RPW8.1 (and its promoter) is functionally distinct from RPW8.2 and may have a higher potential in engineering broad-spectrum resistance in plants.

Characterization of mechanisms of resistance against Didymella pinodes in Pisum spp.

Ascochyta blight caused by Didymella pinodes is a serious disease of pea (Pisum sativum ssp. sativum) to which little resistance has been identified so far. Only incomplete resistance is available in pea germplasm although higher levels of resistance have been reported in related Pisum species. In this study we characterized histochemically the underlying resistance mechanisms in these wild species and in the pea cv. Radley, the pea cultivar with the highest level of resistance to D. pinodes. Resistance was characterized by a reduced success of colony establishment and lesion size. Histologically this was associated with higher frequency of epidermal cell death and protein cross-linking in infected epidermal cells but not with H2O2 accumulation and peroxidase activity.

Colletotrichum truncatum Pathosystem on Capsicum spp: infection, colonization and defence mechanisms

The disease cycle of the chili (Capsicum annuum) anthracnose fungus Colletotrichum truncatum (formerly C. capsici) was elucidated from a study of infection and colonization of seed, leaves and fruit. Microscopic observations of detached leaves and fruit inoculated with a virulent pathotype (F83B), revealed direct cuticle penetration and, intramural, endophytic and necrotrophic phases of colonization. Seedling and fruit ripening stages were very susceptible to infection with the pathogen causing pre- and post-emergence damage and postharvest fruit rot. Furthermore, a quiescent stage, following leaf infection during the vegetative phase of plant growth served as a potential primary inoculum source for fruit infection. Leaf epidermal cells of the resistant C. chinense PBC932 expressed a strong hypersensitive response 48 h after infection (HAI) to both highly virulent (F83B) and less virulent (BRIP 26,974) pathotypes. Infected cells had thickened cell walls, cytoplasm aggregation, and high levels of reactive oxygen species produced 12 HAI. In contrast, the infected epidermal cells of the susceptible C. annuum cultivar Bangchang showed necrosis and rapid cell death after infection by either pathotype. Knowledge of the disease cycle of C. truncatum will be helpful in understanding the behaviour of the pathogen in chili fields which will lead to more efficient application of control measures.

Characterization of three Colletotrichum acutatum isolates from Capsicum spp.

Colletotrichum acutatum causes anthracnose on peppers (Capsicum spp.), resulting in severe yield losses in Taiwan. Fungal isolates Coll-153, Coll-365 and Coll-524 collected from diseased peppers were found to differ in pathogenicity. Pathogenicity assays on various index plants revealed that Coll-524 was highly virulent and Coll-153 was moderately virulent to three commercially available pepper cultivars. Both isolates induced anthracnose lesions and produced abundant conidia. Coll-365 was only weakly virulent on pepper fruit, where it caused small lesions and hardly produced conidia on pepper fruit. However, Coll-365 was highly pathogenic to tomato fruit and mango leaves, where it caused anthracnose lesions and formed acervuli and conidia. All three isolates showed similar abilities in the attachment and germination of conidia, formation of highly branched hyphae and appressoria, penetration of cuticles, and infection of epidermal cells on chili peppers. Coll-365 accumulated less turgor pressure in appressoria but produced higher levels of cutinase and protease activity than Coll-153 and Coll-524 did. All three isolates invaded the neighbouring cells through plasmodesmata in chili peppers and showed similar pectinase or cellulase activities in culture. However, the most virulent strain Coll-524 expressed stronger laccase activity and was more resistant to capsaicin compared to Coll-153 and Coll-365. The three isolates are different in numbers and sizes of double-stranded RNAs. Depending on the cultivar genotypes, cellular resistance of chili pepper to C. acutatum might rely on the ability to restrict penetration, colonization, or conidiation of the pathogen. We conclude that the differences in pathogenicity among the three C. acutatum isolates of pepper are attributed to their ability to colonize the host plant.

Amelioration of radiation-induced skin injury by adenovirus-mediated heme oxygenase-1 (HO-1) overexpression in rats

ObjectiveRadiation-induced skin injury remains a serious concern for radiation therapy. Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme catabolism, has been reported to have potential antioxidant and anti-apoptotic properties. However, the role of HO-1 in radiation-induced skin damage remains unclear. This study aims to elucidate the effects of HO-1 on radiation-induced skin injury in rats.MethodsA control adenovirus (Ad-EGFP) and a recombinant adenovirus (Ad-HO1-EGFP) were constructed. Rats were irradiated to the buttock skin with a single dose of 45 Gy followed by a subcutaneous injection of PBS, 5 × 109 genomic copies of Ad-EGFP or Ad-HO1-EGFP (n = 8). After treatment, the skin MDA concentration, SOD activity and apoptosis were measured. The expression of antioxidant and pro-apoptotic genes was determined by RT-PCR and real-time PCR. Skin reactions were measured at regular intervals using the semi-quantitative skin injury score.ResultsSubcutaneous injection of Ad-HO1-EGFP infected both epidermal and dermal cells and could spread to the surrounding regions. Radiation exposure upregulated the transcription of the antioxidant enzyme genes, including SOD-1, GPx2 and endogenous HO-1. HO-1 overexpression decreased lipid peroxidation and inhibited the induction of ROS scavenging proteins. Moreover, HO-1 exerted an anti-apoptotic effect by suppressing FAS and FASL expression. Subcutaneous injection of Ad-HO1-EGFP demonstrated significant improvement in radiation-induced skin injury.ConclusionsThe present study provides evidences for the protective role of HO-1 in alleviating radiation-induced skin damage in rats, which is helpful for the development of therapy for radiation-induced skin injury.

Expression of a bacterial chitosanase in rice plants improves disease resistance to the rice blast fungus Magnaporthe oryzae

Plant fungal pathogens change their cell wall components during the infection process to avoid degradation by host lytic enzymes, and conversion of the cell wall chitin to chitosan is likely to be one infection strategy of pathogens. Thus, introduction of chitosan-degradation activity into plants is expected to improve fungal disease resistance. Chitosanase has been found in bacteria and fungi, but not in higher plants. Here, we demonstrate that chitosanase, Cho1, from Bacillus circulans MH-K1 has antifungal activity against the rice blast fungus Magnaporthe oryzae. Introduction of the cho1 gene conferred chitosanase activity to rice cells. Transgenic rice plants expressing Cho1 designed to be localized in the apoplast showed increased resistance to M. oryzae accompanied by increased generation of hydrogen peroxide in the infected epidermal cells. These results strongly suggest that chitosan exists in the enzyme-accessible surface of M. oryzae during the infection process and that the enhancement of disease resistance is attributable to the antifungal activity of the secreted Cho1 and to increased elicitation of the host defense response.