Days After Infection Research Articles

'Candidatus Liberibacter asiaticus' infection alters the reflectance profile in asymptomatic citrus plants.

Huanglongbing (HLB) is the primary and most destructive disease affecting citrus, caused by a pathogen transmitted by an insect vector, Diaphorina citri. There are no curative methods for the disease, and rapid and accurate methods are needed for early detection in the field, even before symptoms appear. These will facilitate the faster removal of infected trees, preventing the spread of the bacteria through commercial citrus orchards. It was possible to determine ranges of hyperspectral bands that demonstrated significant differences in relative reflectance between treatments consisting of healthy and infected plants from the first days of evaluation, when plants infected with 'Candidatus Liberibacter asiaticus' (CLas) were still in the asymptomatic stage of the disease. From the Week 2 of evaluation [58 days after infection (DAI) of plants] until the last week, spectral differences were detected in the red edge region (660-750 nm). From the Week 6 onwards (86 DAI), spectral differences between healthy and symptomatic plants were observed in bands close to the visible region (520-680 nm). Spectral differences were detected in the leaves of C. sinensis infected by CLas before the appearance of symptoms, making it feasible to use the hyperspectral sensor to monitor the disease. Our results indicate the need for future studies to validate the use of hyperspectral sensors for managing and detecting HLB in commercial citrus orchards, contributing to the integrated management of the disease. © 2024 Society of Chemical Industry.

Long intergenic non-coding RNAs modulate proximal protein-coding gene expression and tolerance to Candidatus Liberibacter spp. in potatoes

Long intergenic non-coding RNAs (lincRNAs) are emerging as regulators of protein-coding genes (PCGs) in many plant and animal developmental processes and stress responses. In this study, we characterize the genome-wide lincRNAs in potatoes responsive to a vascular bacterial disease presumably caused by Candidatus Liberibacter solanacearum (CLso). Approximately 4397 lincRNAs were detected in healthy and infected potato plants at various stages of zebra chip (ZC) disease progression. Of them, ~65% (2844) were novel lincRNAs, and less than 1% (9) were orthologs of Arabidopsis and rice based on reciprocal BLAST analysis, suggesting species-specific expansion. Among the proximal lincRNAs within 50 kbp from a PCG, ~49% were transcribed from the same strand, while ~39% and ~15% followed convergent (head-to-head) and divergent (tail-to-tail) orientations, respectively. Approximately 30% (1308) were differentially expressed following CLso infection, with substantial changes occurring 21 days after infection (DAI). Weighted Gene Co-expression Network Analysis (WGCNA) of lincRNAs and PCGs identified 46 highly correlated lincRNA–PCG pairs exhibiting co-up or co-downregulation. Furthermore, overexpression of selected lincRNAs in transgenic potato hairy roots resulted in perturbation of neighboring PCG expression and conferred tolerance to CLso infection. Our results provide novel insights into potato lincRNAs’ identity, expression dynamics, and functional relevance to CLso infection.

Comprehensive analysis of hyperspectral features for monitoring canopy maize leaf spot disease

Accurate quantification of hyperspectral features altered by plant disease infection is pivotal for effective disease management. However, the sensitivity of hyperspectral features to plant disease progression remains elusive, primarily because these features are often influenced by plant growth and environmental factors in addition to the specific disease. This study explores the sensitivity of biophysical and spectral features as indicators for maize adaptation to leaf spot disease. Using high-resolution UAV hyperspectral imaging, we captured maize adaptation dynamics over 30 days post-infection. We evaluated the sensitivity and importance of hyperspectral features for disease monitoring, including biophysical parameters retrieved by the PROSAIL model, and spectral features, including spectral reflectance, vegetation indices (VIs), and wavelet features (WFs). Our findings reveal that WFs first indicate disease response as early as 6 days after infection (DAI), followed by VIs at DAI 8, and variations in chlorophyll content (Cab) become apparent by DAI 10. The Cab, plant senescence reflectance index (PSRI), and normalized photosynthetic reflectance index (NPRI) are determined to be important features at the early stage of the disease. Our experimental results show that the different feature sets are complementary at the early and severe stages of the disease. Our classification models integrating Cab, VIs, and WFs showed higher overall accuracy than models using only spectral features or VIs, with a maximum improvement of 9.36 %. However, these feature sets are redundant in the mild and initial severe disease stages, where models using only spectral features achieve the highest overall accuracy of 86.21 %. This study underscores the novel insights by offering an understanding of plant responses to disease infection and enhancing early detection strategies.

Comparative histopathology of virulent and avirulent Meloidogyne javanica populations on susceptible and resistant tomato plants.

The Mi-1.2 gene confers resistance to a wide range of Meloidogyne species, being the most important resistance factor employed in tomato breeding so far. However, many aspects related to the interaction of Mi-1.2-carrying tomato cultivars and virulent/avirulent Meloidogyne populations have not yet been clarified. Herein, comparative histopathological analyses were carried after inoculation of the homozygous (Mi-1.2/Mi-1.2) tomato rootstock 'Guardião' and the susceptible cultivar 'Santa Clara' (mi-1.2/mi-1.2) with virulent and avirulent populations of M. javanica. In the susceptible control, it was possible to visualize second stage juveniles (J2) of avirulent population and feeding sites from 2 to 30 days after infection (DAI) with females reaching maturity at 24-34 DAI. In the resistant rootstock, the Mi-1.2 gene-mediated resistance was related mainly to early defense responses (pre-infection and hypersensitive reaction), which led to an immunity-like phenotype that completely prevented the reproduction of the avirulent Meloidogyne population. On the other hand, J2s of the virulent M. javanica population were able to penetrate roots much more than the avirulent population, migrated and developed normally, showing intense and similar pattern of penetration from 4 to 34 DAI in the root tissues of both resistant and susceptible tomato genotypes. The total numbers of J2, J3, J4, and females counted in 'Santa Clara' for the virulent population of M. javanica were higher than in 'Guardião'.

Mode of inheritance of rice resistance to African rice gall midge

Development of rice (Oryza sativa) varieties with improved traits, like resistance to both biotic and abiotic stresses, is crucial, particularly for sub-Saharan Africa (SSA). Among the biotic stresses, the African rice gall midge (Orseolia oryzivora) is one of the most devastating pests/insects of rice in the region. The objective of this study was to determine the mode of inheritance of resistance to African rice gall midge (AfRGM) as a basis for developing insect resistant rice varieties in the SSA. Four resistant genotypes and four susceptible locally adapted genotypes of rice were crossed in half diallel crossing design. The F2 segregants and their corresponding parents, were evaluated in the cage experiment, against AfRGM in a 4 by 9 alpha lattice design, in three replications. Results showed a significant variation (P<0.05) in rice AfRGM resistance among genotypes. Significant general and specific combining abilities were observed, indicating that both additive and non-additive gene effects were important in rice AfRGM resistance. However, the non-additive effects predominated at 42 and 63 days after infection (DAI). High coefficients of genetic determination in the broad sense (0.96, 0.97 and 0.98, respectively), and moderate narrow sense (0.55, 0.45 and 0.39) at 21, 42 and 63 DAI, were obtained, with a moderate Baker’s ratio of 0.57, 0.46 and 0.40 in the 21, 42 and 63 DAI, respectively; indicating primarily non-additive inheritance among crosses.

A Preliminary Study on the Relationship between Parasitaemia and Cytokine Expression of Peripheral Blood Cells in Trypanosoma vivax-Experimentally Infected Cattle.

Simple SummaryInfections by Trypanosoma vivax in livestock have been reported with increasing frequency worldwide. Nevertheless, information regarding the immune response during the infection is scarce. Regarding that, cytokines play an important role as inflammation modulators, influencing the outcome of trypanosomosis. This study aimed to evaluate host cytokine production during T. vivax infection, in order to assess the increase or decrease of selected cytokines with the cattle’s ability to control the infection. While animals that showed an increase in IL-6 and IFNγ managed T. vivax parasitaemia satisfactorily, cattle that showed reduction of IL-1β, IL-2 and TNFα did not control the parasite multiplication. The presented results are preliminary and shed some light on the role of cytokines during T. vivax-infection.Trypanosoma vivax outbreaks have been reported with increasing frequency worldwide, causing significant economic losses in livestock. Though several studies have suggested that cytokine responses may influence infection caused by Trypanosoma sp., their exact role remains unclear and may vary according to the animal species and parasite strain. The present study aimed to evaluate cytokine expression of peripheral blood cells from three Girolando dairy cows experimentally infected with T. vivax. For this purpose, blood samples were collected prior to the inoculation on the day of inoculation (D0), the day after inoculation (D1), and then every seven days up to 119 days after infection (DAI). Each animal presented a unique pattern of cytokine expression. While a tendency of a Th1 cytokine response was observed during the patent phase (presence of circulating parasites), an increase of Th2 cytokine expression was found at the beginning of the sub-patent phase (low parasitaemia or aparasitaemic periods). In animals that presented a better control of parasitaemia, IL-6 and IFNγ increased during most of the trial period. On the other hand, the cow that presented reduction of IL-1β, IL-2, and TNFα during the entire period did not control parasitaemia properly. A balance between the Th1 and Th2 profile is beneficial for parasite control and animal health. The results found in the present study are a first step towards elucidating the dynamics of cattle’s inflammatory response against T. vivax, requiring future studies focusing on the role of key cytokines on the controlling of parasitaemia in different stages of bovine trypanosomosis.

South American Entamoeba dispar strains produce amoebic liver abscesses with different pathogenicities and evolutionary kinetics

Amoebiasis is a protozoan disease caused by Entamoeba histolytica, and presents a geographic distribution of worldwide amplitude, high incidence, sometimes accompanied by severe clinical manifestations such as amoebic colitis and Amoebic Liver Abscess (ALA), remaining as a public health problem in developing countries. Entamoeba dispar is another species of amoeba that infects approximately 12% of the world's population, and it has previously been classified as noninvasive. However, E. dispar has already been isolated from patients with symptomatic non-dysenteric colitis, as well as its DNA sequences were detected and genotyped in samples from patients with dysenteric colitis, and patients with ALA, suggesting that this species could also be involved in the development of lesions in the large intestine and liver of human beings. In this context, this study aims to evaluate the ability of isolated strains of Entamoeba dispar in South America to cause liver damage, and to better characterize histopathological findings in 3, 8, 12 and 16 days after infection (DAI). Firstly, we assessed whether trophozoites from MCR, ACFN, ICS, ADO and VEJ E. dispar strains, and EGG Entamoeba histolytica strain differed in their in vitro phagocytosis ability, being related to greater ability to phagocyte with greater virulence. Then, we investigate and characterize histopathological changes present in the liver of mice induced by different strains of E. dispar. Our results demonstrated that trophozoites from E. dispar strains are capable of phagocyting human erythrocytes, but in lower amounts than Entamoeba histolytica. In addition, we described and characterized the lesions in different periods after infection by different E. dispar strains, and identified ACFN as the most pathogenic strain, followed by MCR. The large areas of necrosis produced by the ACFN strain as the eighth DAI, which also show high parasitism, led to 100% mortality. On the other hand, the ICS, ADO and VEJ strains did not produce mortality, and this was correlated with the presence of well-developed chronic granulomatous inflammation, necrosis absorption throughout the infection, and regeneration of the liver parenchyma. The greater pathogenicity of the ACFN strain strongly suggests that this strain could be producing higher levels of virulence factors. As the experimental infection, the heterogeneity of biological behavior of different Entamoeba dispar strains could be involved in the development of undiagnosed human clinical conditions.

Over expression of the Q-type ZFP StZFP2 in potato increases resistance to potato late blight (Phytophthora infestans) infection

ABSTRACT Late blight in potato caused by Phytophthora infestans remains a major impediment to potato growers worldwide. Utilization of regulators that affect defence may augment control measures to achieve a basal defence against late blight. This work examines the effect of over-expressing the transcription factor StZFP2 in potato on P. infestans infection. StZFP2 is induced upon infestation by chewing insects such as Manduca sexta and the pathogen P. infestans. StZFP2 was transformed into potato under the control of the CaMV 35S promoter. Three over-expressing lines (OE-StZFP2) resulted in significantly lower lesion size five days after infection (DAI). The increased expression of StZFP2 slowed the spread of infection at 5DAI. Levels of StZFP2 and classic pathogen response marker genes, StPR-1b and StPR-2 were significantly lower in more resistant lines, suggesting that OE-StZFP2 affects this pathogen response.

The Fungus Raffaelea lauricola Modifies Behavior of Its Symbiont and Vector, the Redbay Ambrosia Beetle (Xyleborus Glabratus), by Altering Host Plant Volatile Production.

The redbay ambrosia beetle Xyleborus glabratus is the vector of the symbiotic fungus, Raffaelea lauricola that causes laurel wilt, a highly lethal disease to members of the Lauraceae family. Pioneer X. glabratus beetles infect live trees with R. lauricola, and only when tree health starts declining more X. glabratus are attracted to the infected tree. Until now this sequence of events was not well understood. In this study, we investigated the temporal patterns of host volatiles and phytohormone production and vector attraction in relation to laurel wilt symptomology. Following inoculations with R. lauricola, volatile collections and behavioral tests were performed at different time points. Three days after infection (DAI), we found significant repellency of X. glabratus by leaf odors of infected swamp bay Persea palustris as compared with controls. However, at 10 and 20 DAI, X. glabratus were more attracted to leaf odors from infected than non-infected host plants. GC-MS analysis revealed an increase in methyl salicylate (MeSA) 3 DAI, whereas an increase of sesquiterpenes and leaf aldehydes was observed 10 and 20 DAI in leaf volatiles. MeSA was the only behaviorally active repellent of X. glabratus in laboratory bioassays. In contrast, X. glabratus did not prefer infected wood over healthy wood, and there was no associated significant difference in their volatile profiles. Analyses of phytohormone profiles revealed an initial increase in the amount of salicylic acid (SA) in leaf tissues following fungal infection, suggesting that the SA pathway was activated by R. lauricola infection, and this activation caused increased release of MeSA. Overall, our findings provide a better understanding of X. glabratus ecology and underline chemical interactions with its symbiotic fungus. Our work also demonstrates how the laurel wilt pathosystem alters host defenses to impact vector behavior and suggests manipulation of host odor by the fungus that attract more vectors.

Meloidogyne incognita - rice (Oryza sativa) interaction: a new model system to study plant-root-knot nematode interactions in monocotyledons.

BackgroundPlant-parasitic nematodes developed strategies to invade and colonize their host plants, including expression of immune suppressors to overcome host defenses. Meloidogyne graminicola and M. incognita are root-knot nematode (RKN) species reported to damage rice (Oryza sativa L.) cultivated in upland and irrigated systems. Despite M. incognita wide host range, study of the molecular plant - RKN interaction has been so far limited to a few dicotyledonous model plants. The aim of this study was to investigate if the rice cv. Nipponbare widely used in rice genomic studies could be used as a suitable monocotyledon host plant for studying M. incognita pathogenicity mechanisms. Here we compared the ability of M. graminicola and M. incognita to develop and reproduce in Nipponbare roots. Next, we tested if RKNs modulates rice immunity-related genes expression in galls during infection and express the Mi-crt gene encoding an immune suppressor.ResultsRoot galling, mature females, eggs and newly formed J2s nematodes were obtained for both species in rice cultivated in hydroponic culture system after 4-5 weeks. Meloidogyne graminicola reproduced at higher rates than M. incognita on Nipponbare and the timing of infection was shorter. In contrast, the infection characteristics compared by histological analysis were similar for both nematode species. Giant cells formed from 2 days after infection (DAI) with M. graminicola and from 6 DAI with M. incognita. Real-time PCR (qRT-PCR) data indicated that RKNs are able to suppress transcription of immune regulators genes, such as OsEDS1, OsPAD4 and OsWRKY13 in young galls. Four M. incognita reference genes (Mi-eif-3, Mi-GDP-2, Mi-Y45F10D.4, and Mi-actin) were selected for normalizing nematode gene expression studies in planta and in pre-parasitic J2s. Meloidogyne incognita expressed the immune suppressor calreticulin gene (Mi-crt) in rice roots all along its infection cycle.ConclusionRKNs repress the transcription of key immune regulators in rice, likely in order to lower basal defence in newly-formed galls. The calreticulin Mi-CRT can be one of the immune-modulator effectors secreted by M. incognita in rice root tissues. Together, these data show that rice is a well suited model system to study host- M. incognita molecular interactions in monocotyledons.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-014-0023-4) contains supplementary material, which is available to authorized users.

Castor (Ricinus communis L.) Rc-LOX5 plays important role in wilt resistance

Phyto-oxylipins are a group of biologically active molecules that play an important role in plant defense. Their production begins with the oxygenation of polyunsaturated fatty acids by lipoxygenases (LOXs; EC 1.13.11.12) to form 9- or 13-hydroperoxides. These are substrates for several enzymes involved in the synthesis of final oxylipins, which can act as signal molecules and/or direct antimicrobials. Recent completion of the castor bean genome sequence now permits genome-wide analysis of the LOX gene family in castor as well as comparison with LOX in Arabidopsis. We identified 12 candidate LOX genes in the castor bean genome. Phylogenetic analysis indicated that these LOX members cluster into two groups, designated types 1 and 2, as expected from previous studies. Out of which six LOX gene specific primers were designed to amplify castor LOX genes i.e. LOX1, LOX2, LOX3, LOX4, LOX5 and Dox. Sequence analysis showed conserved five iron binding sites in the LOX domain of all the Rc-LOX, however, only LOX5 contained consensus (positions 547, 556, and 715) histidines residue. Expression analysis of LOX2, 3, 4, 5 and DOX genes in resistant and susceptible genotypes of castor at 0 days after infection (DAI), 5 DAI and 10 DAI (30 days after sowing) was carried out using quantitative real time (RT)-PCR during castor bean–Fusarium oxysporium f. sp. ricini interaction. Results suggest that 2 (LOX2 and LOX5) of 6 Rc-LOX genes were detectable. Resistant genotypes (48-1 and SKP-84) exhibited appreciably higher expression of LOX5 during castor bean–F. oxysporium interaction, which further suggest the participation of Rc-LOX5, a type-1 LOX predicted to be 9-LOX, in wilt resistance.

Antioxidant metabolism in pearl millet genotypes during compatible and incompatible interaction with downy mildew pathogen

In this study, the ascorbic acid content, lipid peroxidation product, reactive oxygen generation and scavenging enzyme activities were determined in pearl millet [Pennisetum glaucum (L.) R.Br.] leaves. These parameters were analysed at two stages: (i) pre-infection [45 days after sowing (DAS)] and (ii) post-infection [7 days after infection (DAI), i.e. 57 DAS]. Lipid peroxidation product (malondialdehyde content) was recorded higher in compatible interaction at pre-infection stage while it was increased in incompatible interaction at post-infection stage. Resistant genotypes had higher ascorbic acid content at both the stages of analysis. Superoxide dismutase (SOD) activity was higher in susceptible genotypes at pre-infection but after infection it was found to be higher in resistant genotypes. Ascorbate peroxidase, catalase (CAT) and lipoxygenase activities were higher in resistant genotypes at both the stages of analysis. Native PAGE isozyme banding pattern of SOD, CAT, APX and esterase showed some inducible band(s) due to disease infection.

Development of Graphidium strigosum (Nematoda, Haemonchidae) in its natural host, the rabbit (Oryctolagus cuniculus) and comparison with several Haemonchidae parasites of ruminants

The morphogenesis (studied for the first time) and the chronology of the life cycle of Graphidium strigosum (Dujardin, 1845) were studied in detail in its natural host, Oryctolagus cuniculus. Naive rabbits were each infected per os with G. strigosum infective larvae (L3). Animals were euthanized each day for the first 10 days after infection (DAI), then every 2 days from 12 to 40 DAI. The free living period lasted 5-8 days at 24°C. By 1 DAI, all the larvae were exsheathed in the stomach. The third molt occurred between 9 and 17 DAI. The last molt occurred between 24 and 32 DAI. The prepatent period lasted 42-44 DAI, while the patent period lasted at least 13 months. For each experiment, the morphology of the different stages of the life cycle was described. The chronology of the G. strigosum life cycle and its morphogenesis were compared to those of different Haemonchidae parasites of ruminants (Ostertagia ostertagi, Teladorsagia circumcincta, Haemonchus contortus, and Haemonchus placei) in their natural hosts.

Estimated egg production of Fasciola gigantica (Japanese strain) in goats experimentally infected with 50 metacercariae

Abstract Egg production capacity in Fasciola gigantica (Japanese strain) was estimated from egg count data obtained by the experimental infection of two goats. The goats were inoculated with a single dose of 50 metacercariae. The first goat was necropsied 132 days after infection (DAI) and the second goat 732 DAI. After patency, daily faecal production was collected and weighed and number of eggs per gram was counted. At necropsy, 23 flukes were recovered from the liver of the first goat, and five from the second goat. The mean number of eggs produced per day per worm (± 95 % confidence limits) was 9 477.9 (± 764.92) for the first goat at 106 to 132 DAI, and 8,064.1 (± 416.49) at 195 to 561 DAI for the second goat. The number of eggs produced per day per worm in F. gigantica (Japanese strain) has thus reached values ranged from approximately 8 000 to 10 000 eggs.

Resistance to Meloidogyne incognita expresses a hypersensitive-like response in Coffea arabica

Root-knot nematodes (RKN) are obligate parasite species of the genus Meloidogyne that cause great losses in Arabica coffee (Coffea arabica L.) plantations. Identification of resistant genotypes would facilitate the improvement of coffee varieties aiming at an environmental friendly and costless nematode control. In this work, the C. arabica genotype ‘UFV 408-28’ was found to be resistant to the most destructive RKN species M. incognita. Pathogenicity assays indicated that the highly aggressive populations of M. incognita races 1, 2 and 3 were not able to successfully reproduce on ‘UFV 408-28’ roots and displayed a low gall index (GI = 2). An average reduction of 87% reduction of the M. incognita population was observed on ‘UFV 408-28’ when compared to the susceptible cultivar ‘IAC 15’. By contrast, ‘UFV 408-28’ was susceptible to the related species M. exigua and M. paranaensis (GI = 5 and 4, respectively). Histological observations performed on sections of UFV408-28 roots infected with M. incognita race 1 showed that nematode infection could be blocked right after penetration or during migration and establishment stages, at 6 days, 7 days and 8 days after infection (DAI). Fluorescence and bright field microscopy observations showed that root cells surrounding the nematodes exhibited HR-like features such as accumulation of phenolic compounds and a necrotic cell aspect. In the susceptible ‘IAC 15’ roots, 6 DAI, feeding sites contained giant cells with a dense cytoplasm. Necrotic cells were never observed throughout the entire infection cycle. The HR-like phenotype observed in the ‘UFV 408-28’—M. incognita interaction suggests that the coffee resistance may be mediated by a R-gene based immunity system and may therefore provide new insights for understanding the molecular basis of RKN resistance in perennial crops.

Matrix metalloproteinases with gelatinolytic activity induced by Paracoccidioides brasiliensis infection

Matrix metalloproteinases (MMPs) modulate extracellular matrix turnover, inflammation and immunity. We studied MMP-9 and MMP-2 in experimental paracoccidioidomycosis. At 15 and 120 days after infection (DAI) with virulent Paracoccidioides brasiliensis, MMP-9 was positive by immunohistochemistry in multinucleated giant cells, in mononuclear cells with macrophage and lymphocyte morphologies and also in fungal cells in the lesions of susceptible and resistant mice. Using gelatin zymography, pro- and active MMP-9 and active MMP-2 were detected in all infected mice, but not in controls. Gelatinolytic activity was not observed in P. brasiliensis extracts. Semiquantitative analysis of gelatinolytic activities revealed weak or absent MMP-2 and strong MMP-9 activity in both mouse strains at 15 DAI, declining at 120 DAI. Avirulent P. brasiliensis-infected mice had residual lesions with MMP-9-positive pseudoxantomatous macrophages, but no gelatinase activity at 120 DAI. Our findings demonstrate the induction of MMPs, particularly MMP-9, in experimental paracoccidioidomycosis, suggesting a possible influence in the pattern of granulomas and in fungal dissemination.

Secondary bacterial infection in plasma endotoxin levels and the acute‐phase response of mice infected withTrypanosoma brucei brucei

Murine Trypanosoma brucei brucei infection leads to elevated plasma endotoxin-like activity levels not related to parasitaemia levels accompanied by the development of acute-phase response and increased plasma levels of serum amyloid P (SAP) and haptoglobin (Hp). To determine the source of the endotoxin-like activity and role of secondary bacterial infection in the pathogenesis of trypanosomosis, infected mice were treated with the antibiotic ciprofloxacin. Plasma endotoxin-like activity levels, irrespective of treatment, were elevated three- to fourfold, beginning 7 days after infection. Plasma protein concentrations increased markedly following infection from 7 days after infection (DAI). Peak Hp and SAP concentrations in ciprofloxacin-treated and -untreated infected mice were attained 7 and 14 DAI, respectively. Thereafter, both protein levels gradually declined until the end of the experiment, but Hp levels for non-treated mice declined up to 21 DAI and thereafter significantly increased on 28 and 35 DAI. Whole-trypanosome lysate and the membrane-enriched fraction demonstrated endotoxin-like activity, with the former having higher levels. The results suggest that the endotoxin-like activity in trypanosome fractions and plasma of infected mice is due to the trypanosome. Further elevation of haptoglobin during the late stages of infection in non-treated mice suggests the involvement of secondary bacterial infection.

Nitric oxide participation in granulomatous response induced by Paracoccidioides brasiliensis infection in mice

The role of nitric oxide (NO) in granulomas of Paracoccidioides brasiliensis-infected inducible NO synthase-deficient C57BL/6 mice (iNOS KO) and their wild-type counterparts and its association with osteopontin (OPN) and matrix metalloproteinases (MMPs) was studied. At 15 days after infection (DAI), iNOS KO mice showed compact and necrotic granulomas with OPN+ macrophages and multinucleated giant cells, whereas wild-type mice developed loose granulomas with many fungi and OPN+ cells distributed throughout the tissue. In addition, high OPN levels and fungal load were observed in iNOS KO mice. Both experimental groups had MMP-9 activity. At 120 DAI, iNOS KO had smaller granulomas with OPN+ cells, lower OPN levels, lower fungal load and decreased MMP-9 activity compared with wild-type mice. These findings suggest that NO has an important role in granuloma modulation, by controlling OPN and MMP production, as well as by inducing loose granulomas formation and fungal dissemination, resulting, at later phases, in progression of paracoccidioidomycosis.

Infection of Chinese cabbage by Plasmodiophora brassicae leads to a stimulation of plant growth: impacts on cell wall metabolism and hormone balance

The importance of plant hormones in clubroot infection has long been recognized. The morphological changes, such as cell division and cell elongation leading to gall formation are triggered in the early stages of infection. We analysed cell expansion by localizing Xyloglucan endoTransglucosylase/Hydrolase (XTH)-action and screened the endogenous concentrations of several classes of phytohormones by mass spectrometry in the early stages of Plasmodiophora brassicae infection in Chinese cabbage (Brassica rapa spp. pekinensis). Infected plants showed a general transient growth promotion early in infection. Furthermore a clear XTH action was visible in the epidermal layer of infected roots. Complex changes in the endogenous phytohormone profile were observed. Initially infection resulted in an increased total auxin pool. The auxin increase, together with an increased XTH action, results in wall loosening and consequently cell expansion. When the first secondary plasmodia are formed, thirteen days after infection (DAI), can be considered a switch point in phytohormone metabolism. Twenty-one DAI the plasmodia might act as a plant hormone sink resulting in a reduction in the active cytokinin pool and a lower indole-3-acetic acid content in the infected plants.

Effect of Pratylenchus zeae infection on the expression of isozyme activities in resistant and susceptible sugarcane clones

AbstractThe constitutive levels of both phenylalanine ammonia-lyase (PAL) and tyrosine ammonia-lyase (TAL) activities in roots and leaves were found to be greater in sugarcane clones resistant to the lesion nematode Pratylenchus zeae than in susceptible clones. Investigations on the sequential development of PAL and TAL activities were undertaken in resistant (Co 7717) and susceptible (CoC 671) sugarcane clones infected with P. zeae. PAL activity in both roots and leaves of the resistant clone showed a maximum percentage increase, compared with non-infected controls, at 35 and 14 days after infection (DAI), respectively. However, in the susceptible clone the maximum percentage decrease compared with the non-infected clone was observed at 3 and 14 DAI. TAL activity in the resistant clone showed the maximum percentage increase compared with the non-infected control at 28 DAI in roots and 7 DAI in leaves, whereas in the susceptible clone the maximum percentage decrease compared with the non-infected control was at 35 DAI in roots and 28 DAI in leaves. In experiments on the induction of enzyme response to infection by P. zeae, eight resistant and eight susceptible clones were analysed 14 days after P. zeae infection. Among the eight resistant clones six showed increased PAL activity compared with non-infected clones. Four susceptible infected clones showed a decrease as compared with non-infected clones, while the remaining four infected clones showed an increased enzyme activity compared to non-infected clones. Superoxide dismutase (SOD) activity increased quantitatively in both roots and leaves from nematode-infected susceptible clones compared to non-infected clones. The SOD activity decreased in roots and leaves from nematode infected resistant clones, when compared to the non-infected-resistant clones. In native PAGE analysis of SOD and esterase activities the major differences between infected and non-infected clones of resistant and susceptible sugarcane were observed in low and medium electrophoretic mobility ranges.