Pyridoxal phosphate, pyridoxamine phosphate, and folic acid based on ceRNA regulatory network as potential biomarkers for the diagnosis of pulmonary tuberculosis.

BACKGROUND: Pulmonary tuberculosis (TB) is a serious disease burden worldwide, and its effective early diagnosis is still facing challenges. Knowledge, acquired from multi-omics integration analysis about the association between different types of differentially expressed molecules in the plasma of TB patients and the disease traits, is anticipated to improve the accuracy of TB diagnosis through the "integrative pattern". METHODS: In this study, the lncRNA-miRNA-mRNA interaction network was constructed based on the competing endogenous RNA (ceRNA) hypothesis by integrating our previous data sets of lncRNA, mRNA, miRNA, and metabolites. Moreover, the key regulatory axis was established by co-expression analysis and verified at the level of metabolites. RESULTS: A ceRNA regulatory network consisting of 23 lncRNAs, 10 miRNAs, and 113 mRNAs was constructed. The analysis results suggested that lncRNA (OSBPL10-AS1), miRNA (has-miR-485-5p), and mRNA (SLC23A2) might be involved in the regulation of vitamin metabolism in patients with TB. Metabolite analysis showed that compared with the normal control group, TB patients had abnormal vitamin metabolism, and the expression levels of pyridoxal phosphate, pyridoxamine phosphate, and folic acid were significantly different between the two groups (p < 0.05). CONCLUSION: Integrated multi-omics analysis showed that vitamin metabolism disorder may be one of the pathological characteristic of TB. OSBPL10-AS1, hsa-miR-485-5p, SLC23A2, pyridoxal phosphate, pyridoxamine phosphate, and folic acid may collectively constitute the "integrative pattern" of multiple biomarkers, which may provide an accurate diagnosis of TB.

A group of serum proteins as potential diagnostic biomarkers for Yin-deficiency-heat syndrome.

Yin-deficiency-heat (YDH) syndrome is a very common subhealth status in Traditional Chinese Medicine. However, currently, there is no unified standard for diagnosing YDH syndrome. We applied the iTRAQ-2D LC-MS/MS method to explore the potential of serum protein profiles as biomarker for YDH syndrome. A total of 120 differentially expressed proteins (79 downregulated and 41 upregulated) were identified by the proteomic profiling. The results of KEGG pathway analysis showed that the functions of the differentially expressed proteins were mainly involved in complement and coagulation cascades. The clinical data showed that YDH syndrome was closely related to inflammation and coagulation, compared with the healthy controls. The ELISA validation results indicated that the expression levels of ALB, CFI, and KLKB1 were downregulated in the YDH syndrome group (p < .05). Moreover, we established a decision tree model based on the combination of these three proteins and achieved a sensitivity of 87.5%, a specificity of 84.4%, and AUC of 0.891. The results indicated that the combination of ALB, CFI, and KLKB1 may serve as potential biomarkers for diagnosing YDH syndrome. Our study can provide a new method for YDH syndrome diagnosis, and may also provide an experimental basis to understand the molecular mechanism of YDH syndrome.

Screening of potential biomarkers for Yin-deficiency-heat syndrome based on UHPLC-MS method and the mechanism of Zhibai Dihuang granule therapeutic effect.

BACKGROUND: Yin-deficiency-heat (YDH) syndrome is a subhealth state of the individual, mainly manifested as oral ulcers, dry mouth, constipation, and other symptoms. Zhibai Dihuang granule (ZDG), as a classic traditional Chinese medicine, is effective in treating YDH syndrome. We screened the potential biomarkers for diagnosing YDH syndrome, and explored the mechanisms of the therapeutic effect of ZDG. METHODS: Plasma samples from the Pinghe (PH, healthy control) group, the Shanghuo (SH, YDH syndrome) group, and the ZDG treated group (therapeutic group) were analyzed by using metabolomics profiling. The data were analyzed by multivariate statistical and bioinformatics analyses. RESULTS: We screened four differential metabolites such as, decanoylcarnitine, dodecanoylcarnitine, phosphatidylcholine (PC), and Aspartate (Asp) Arginine (Arg) Proline (Pro) in the SH group and the PH group. The results showed that the combination of above four metabolites could serve as a potential biomarker for the early diagnosis of YDH syndrome. The metabolites decanoylcarnitine and glucose were found to be differentially expressed in the YDH syndrome group and tended to be normalized after ZDG treatment. CONCLUSION: The increased levels of four differential metabolites (decanoylcarnitine, dodecanoylcarnitine, PC, and Asp Arg Pro) revealed that individuals with YDH syndrome may have increased energy metabolism in the body, which could lead to disorders of fatty acids ß-oxidation and immune function. The levels of two differential metabolites including decanoylcarnitine and glucose returned to normal after ZDG treatment, indicating that ZDG could treat YDH syndrome by regulating glucose metabolism and fatty acids ß-oxidation. Our study provides a new method for the diagnosis of YDH syndrome, and may provide theoretical basis for novel therapeutic strategies of YDH syndrome.

Serum proteins TGFBI, PCSK9, and CCL14 are potential biomarkers for different traditional Chinese medicine syndromes of multidrug-resistant tuberculosis.

Patients with multidrug-resistant tuberculosis (MDR-TB) tend to have a long course of anti-TB treatment and severe side effects. Traditional Chinese Medicine (TCM) has a synergistic effect in attenuation of MDR-TB. However, the lack of objective biological standards to classify and diagnose MDR-TB TCM syndromes could result in less effective TCM treatment. Therefore, in this study, we identified differentially expressed proteins (DEPs) in serum of individuals with MDR-TB TCM syndromes by applying isobaric tags for relative and absolute quantification coupled with two-dimensional liquid chromatography-tandem mass spectrometry (iTRAQ-2DLC-MS/MS) method and bioinformatics analysis. The functional analysis of DEPs was also performed. Additionally, DEPs among three different TCM syndromes of MDR-TB were validated by enzyme-linked immunosorbent assay (ELISA). Finally, a receiver operating characteristic (ROC) curve was performed to estimate the diagnostic ability of DEPs. A total of 71 DEPs were identified in the three different MDR-TB TCM syndrome groups such as the pulmonary Yin deficiency (PYD) syndrome group, the Hyperactivity of Fire due to Yin deficiency (HFYD) syndrome group, and the deficiency of Qi and Yin (DQY) syndrome group. The results showed that the expression level of transforming growth factor-beta-induced protein ig-h3 (TGFBI) was lower in the PYD syndrome group (p = .002), the proprotein convertase subtilisin/kexin type 9 (PCSK9) was overexpressed in the HFYD syndrome group (p < .0001), and the C-C motif chemokine ligand 14 (CCL14) expression level was reduced in the DQY syndrome group (p = .004). Our study demonstrated that serum TGFBI, PCSK9, and CCL14 may serve as potential novel biomarkers for PYD syndrome, HFYD syndrome and DQY syndrome of MDR-TB, respectively. The study provides a biological basis for MDR-TB TCM syndromes classification and can be of great significance for the treatment of different TCM syndromes.

Study on potential biomarkers of energy metabolism-related to early-stage Yin-deficiency-heat syndrome based on metabolomics and transcriptomics.

Yin-deficiency-heat (YDH) syndrome is a common sub-health state of the human body in traditional Chinese medicine (TCM). However, due to the lack of objective quantitative diagnostic indicators, patients with early-stage YDH syndrome cannot be treated in time and can develop a pathological (disease) state. Therefore, it is necessary to apply modern diagnostic techniques in order to identify the biological markers for the diagnosis of early-stage YDH syndrome. In the present study, we performed Solexa sequencing and non-targeted metabolomics analysis using high-performance liquid chromatography coupled with mass spectrometry to screen differentially expressed mRNAs and differential metabolites in individuals with early-stage YDH syndrome and healthy controls. Bioinformatics methods were used to perform enrichment analysis of differentially expressed mRNAs and differential metabolites for biological functions and signaling pathways. Furthermore, we found that differentially expressed mRNAs and differential metabolites were related to energy metabolism. Real-time PCR was used to validate the mRNA expression in the serum of subjects with early-stage YDH syndrome. We found that the mitochondrially encoded NADH dehydrogenase 2 (MT-ND2) mRNA was differentially expressed in the serum of individuals with early-stage YDH syndrome. Receiver operating characteristic (ROC) curve and logistic regression analysis were used to evaluate the efficacy of the diagnostic model based on eight differential metabolites. We combined the three metabolites such as Glycine, Sphingomyelin, and Isocitrate to establish the diagnostic model with a sensitivity of 0.853 and a specificity of 0.800. The combination of the above three metabolites may serve as a potential biomarker for the diagnosis of early-stage YDH syndrome. Our study reveals potential biomarker for the diagnosis of early-stage YDH syndrome and also provides a new method for the quantification and objectification of TCM syndromes.

Plasma metabolites Xanthine, 4-Pyridoxate, and d-glutamic acid as novel potential biomarkers for pulmonary tuberculosis.

BACKGROUND: The lack of rapid and efficient diagnostic methods has been one of the most frustrating challenges in controlling the pulmonary tuberculosis (TB) epidemic. This study was aimed to identify novel non-invasive biomarkers for pulmonary TB. METHODS: The subjects in this study were divided into four groups: the pulmonary TB group, the community-acquired pneumonia (CAP) group, the lung cancer (LC) group, and the normal control (NC) group. Plasma small molecule metabolites were investigated in each group by using ultra-high performance liquid chromatography coupled with Q Exactive mass spectrometry. Multivariate statistical methods and bioinformatics were used to analyze the data. RESULTS: We identified three differential plasma metabolites such as, Xanthine, 4-Pyridoxate and d-glutamic acid in the pulmonary TB group, compared to the other groups (CAP, LC and NC). The pathway enrichment analysis indicated that the energy source in pulmonary TB was multi-center, which might be involved in maintaining the reproductive ability and virulence of Mycobacterium tuberculosis. CONCLUSION: The results suggested that Xanthine, 4-Pyridoxate, and d-glutamic acid may serve as potential biomarkers for pulmonary TB. The present study provides experimental basis for developing potential biomarkers of pulmonary TB.

l-Histidine, arachidonic acid, biliverdin, and l-cysteine-glutathione disulfide as potential biomarkers for cured pulmonary tuberculosis.

Lack of laboratory standards for cured tuberculosis (TB) can lead to early discharge of untreated TB patients from the hospital, resulting in increased risk of TB spread and of developing drug resistant Mycobacterium tuberculosis (Mtb). We used ultra-high performance liquid chromatography coupled with mass spectrometry (LC-MS) to detect heparin anticoagulant in plasma of untreated TB patients, two-month treated TB patients, cured TB subjects, and healthy controls. Screening of differentially expressed metabolites resulted in identification of four differentially expressed metabolites such as, l-Histidine, Arachidonic acid (AA), Biliverdin, and l-Cysteine-glutathione disulfide after 6 months of TB treatment. Among them, l-Cysteine-glutathione disulfide and AA could be identified after 2 months of TB treatment. We established a cured TB model with an area under the curve (AUC) of 0.909 (95% CI, 0.802-0.970), 86.2% sensitivity, and 85.2% specificity. The diagnostic model fitted from the four differential metabolites in combination (l-Histidine, AA, Biliverdin, and l-Cysteine-glutathione disulfide) can be used as potential biomarkers for cured TB. Our study provided laboratory standards for hospital discharge of TB patients, as well as experimental basis for evaluating the efficacy of anti-TB drugs.

Screening and identification of potential protein biomarkers for evaluating the efficacy of intensive therapy in pulmonary tuberculosis.

This research aimed to discover potential biomarkers for evaluating the therapeutic efficacy of intensive therapy in pulmonary tuberculosis (TB). Protein profiles in 2-months intensively treated TB patients, untreated TB patients, and healthy controls were investigated with iTRAQ-2DLC-MS/MS technique. 71 differential proteins were identified in 2-months intensively treated TB patients. Significant differences in complement component C7 (CO7), apolipoprotein A-IV (APOA4), apolipoprotein C-II (APOC2), and angiotensinogen (ANGT) were found by ELISA validation. CO7 and ANGT were also found significantly different in sputum negative patients, compared with sputum positive patients after intensive treatment. Clinical analysis showed that after 2-months intensive treatment several indicators were significantly changed, and the one-year cure rate of sputum negative patients were significantly higher than sputum positive patients. Diagnostic models consisting of APOC2, CO7 and APOA4 were established to distinguish intensively treated TB patients from untreated TB patients and healthy controls with the AUC value of 0.910 and 0.935. Meanwhile, ANGT and CO7 were combined to identify sputum negative and sputum positive TB patients after intensive treatment with 89.36% sensitivity, 71.43% specificity, and the AUC value of 0.853. The results showed that APOC2, CO7, APOA4, and ANGT may be potential biomarkers for evaluating the efficacy of intensive anti-TB therapy.

The Chinese herbal formula Zhibai Dihuang Granule treat Yin-deficiency-heat syndrome rats by regulating the immune responses.

ETHNOPHARMACOLOGICAL RELEVANCE: Zhibai Dihuang Granule (ZDG), a traditional Chinese medicine (TCM) made from eight Chinese herbs, has been classically used to treat Yin-deficiency-heat (YDH) syndrome. ZDG is well known with the therapeutic efficacy of nourishing Yin and decreasing internal heat in clinic, but the mechanism of ZDG's therapeutic effect is still not clear. MATERIALS AND METHODS: High doses of triiodothyronine (T3) were given intraperitoneally to induce Hyperthyroid YDH syndrome in SD rats. The animals were then treated with ZDG for one week. The iTRAQ-coupled with two-dimensional liquid chromatography-tandem mass spectrometry (2D LC-MS/MS) technique was used to screen the differentially expressed serum proteins between ZDG treated rats and YDH syndrome rats. The differentially expressed proteins were analyzed by bioinformatics method and were verified by enzyme-linked immunosorbent assay (ELISA). RESULTS: A total of 55 differentially expressed proteins were identified, including 23 up-regulated proteins (>1.25 fold, p < 0.05) and 32 down-regulated proteins (<0.80 fold, p < 0.05). Among the differentially expressed proteins, 26 proteins returned to normal after ZDG treatment. Bioinformatics analysis showed that these proteins were mainly involved in immune response, including regulation of immune system process, complement activation, and humoral immune response mediated by circulating immunoglobulin. ELISA revealed significantly increased levels of Zinc-alpha-2-glycoprotein (Azgp1), L-selectin, C-reactive protein (Crp), Plasminogen (Plg), Kininogen 1 (Kng1), and significantly decreased levels of Mannose binding lectin 2 (Mbl2) and Complement C1qb chain (C1qb) in ZDG treated rats compared with YDH syndrome rats. Bioinformatics analyses indicated that Azgp1 participated in antigen processing and presentation, Crp, C1qb, and Mbl2 were involved in complement activation, while L-selectin, Plg, and Kng1 were involved in regulating the inflammatory response. CONCLUSIONS: Our study provides experimental evidence to understand the therapeutic mechanism of ZDG in YDH syndrome. The results suggested that ZDG may regulate the complement activation and inflammatory response, and promote the ability to recognize antigens to alleviate YDH syndrome.

Screening and identification of four serum miRNAs as novel potential biomarkers for cured pulmonary tuberculosis.

Rapid and efficient methods for the determination of cured pulmonary tuberculosis (TB) are lacking. We screened serum miRNAs using the Solexa sequencing method among untreated TB patients, two-month treated TB patients, cured TB patients, and healthy controls. A total of 100 differentially expressed miRNAs were identified in cured TB patients, including 37 up-regulated (fold change >1.50, P < 0.05) and 63 down-regulated (fold change <0.60, P < 0.05) miRNAs. Gene ontology (GO) enrichment analysis revealed that most of the predicted genes were present in the nucleus with a strong protein binding function. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis strongly suggested alterations in the metabolic pathways. Following quantitative real time chain reaction (qRT-PCR), significantly reduced expression levels of miR-21-5p (0.30, P < 0.001), miR-92a-3p (0.63, P < 0.001), and miR-148b-3p (0.17, P < 0.001) were found in the cured TB patients compared with the untreated TB patients, while significantly increased expression levels of miR-21-5p (2.09, P = 0.001), miR-92a-3p (1.40, P = 0.005), and miR-148b-3p (4.80, P = 0.003) were found in the untreated TB patients compared with the healthy controls. And significantly increased level of miR-125a-5p was found between two-month treated TB patients and untreated TB patients (1.81, P = 0.004). We established a cured TB model with 83.96% accuracy by four miRNAs (miR-21-5p, miR-92a-3p, miR-148b-3p, and miR-125a-5p), and also established a diagnostic model with 70.09% accuracy. Our study provides experimental data for establishing objective indicators of cured TB, and also provides a new experimental basis to understand the pathogenesis and prognosis of TB.

iTRAQ-based proteomic analysis to identify the molecular mechanism of Zhibai Dihuang Granule in the Yin-deficiency-heat syndrome rats.

BACKGROUND: Zhibai Dihuang Granule (ZDG) is a traditional Chinese medicine which has been used to treat Yin-deficiency-heat (YDH) syndrome for thousands of years in China. However, little work has been conducted to explore the molecular mechanism of ZDG in YDH syndrome, and the processes of YDH syndrome prevention and treatment have been developed slowly. The present study was aimed to explore the therapeutic mechanism of ZDG on YDH syndrome. METHODS: The YDH syndrome rats were induced by hot Chinese herbs, then treated by ZDG orally for 1 week. Body weight was measured every 2 days. After sacrifice, blood samples were collected and the thymus, adrenal glands, spleen, and liver were immediately removed and weighed. iTRAQ-based proteomics approach was applied to explore the serum protein alterations with the treatment of ZDG, and to investigate the underlying mechanism of ZDG in treating YDH syndrome. RESULTS: The body weights of YDH syndrome rats were significantly decreased compared with control group, and increased in ZDG treated rats. The relative weights of thymus in YDH syndrome rats were increased compared with the control rats, and significantly decreased in after ZDG treatment. In the proteomic analyses, seventy-one proteins were differentially expressed in the YDH syndrome group and the ZDG treated group, including 10 up-regulated and 61 down-regulated proteins. Gene ontology analysis revealed that the differentially expressed proteins were mostly related to immune response, and pathway enrichment analysis showed that these proteins were enriched in coagulation and complement cascades. Enzyme-linked immunosorbent assay was performed to detect the protein levels in coagulation and complement cascades, and the results showed that complement component 5 levels were significantly increased, while fibrinogen gamma chain levels were significantly decreased in the ZDG treated group. CONCLUSIONS: We found that ZDG treatment could lead to proteins alteration in immune response, especially in coagulation and complement cascades. ZDG can up-regulate the proteins in the complement cascade to eliminate pathogens, and down-regulate the proteins in the coagulation cascade to suppress inflammation. Our study provides experimental basis to understand the therapeutic mechanism of ZDG and revealed that ZDG can regulate coagulation and complement cascades in treating YDH syndrome.

Screening and identification of lncRNAs as potential biomarkers for pulmonary tuberculosis.

Pulmonary tuberculosis (TB) is among the diseases with the highest morbidity and mortality worldwide. Effective diagnostic methods for TB are lacking. In this study, we investigated long non-coding RNAs (lncRNAs) in plasma using microarray and the potential diagnostic value of lncRNAs for TB. We found a total of 163 up-regulated lncRNAs and 348 down-regulated lncRNAs. Gene ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) and coding-noncoding co-expression (CNC) analyses showed that functions of differentially expressed lncRNAs were mainly enriched in the regulation of alpha-beta T cell activation and the T cell receptor signalling pathway. Four differentially expressed lncRNAs, NR_038221 (fold change = 3.79, P < 0.01), NR_003142 (fold change = 1.69, P < 0.05), ENST00000570366 (fold change = 3.04, P < 0.05), and ENST00000422183 (fold change = 2.11, P < 0.001), were verified using RT-qPCR. Among those, NR_038221, NR_003142, and ENST00000570366 were found to be up-regulated, while ENST00000422183 was down-regulated. The value of the area under the curve (AUC) for the diagnostic model consisting of the four lncRNAs was 0.845 (sensitivity = 79.2%, specificity = 75%). We further predicted 85 mRNAs and 404 miRNAs that potentially interact with these lncRNAs. Our study revealed the potential value of lncRNAs as biomarkers for early diagnosis of TB and the underlying mechanisms of these abnormally expressed lncRNAs in the pathogenesis of TB.

Serum amyloid A, protein Z, and C4b-binding protein ß chain as new potential biomarkers for pulmonary tuberculosis.

The aim of this study was to discover novel biomarkers for pulmonary tuberculosis (TB). Differentially expressed proteins in the serum of patients with TB were screened and identified by iTRAQ-two dimensional liquid chromatography tandem mass spectrometry analysis. A total of 79 abnormal proteins were discovered in patients with TB compared with healthy controls. Of these, significant differences were observed in 47 abnormally expressed proteins between patients with TB or pneumonia and chronic obstructive pulmonary disease (COPD). Patients with TB (n = 136) exhibited significantly higher levels of serum amyloid A (SAA), vitamin K-dependent protein Z (PROZ), and C4b-binding protein ß chain (C4BPB) than those in healthy controls (n = 66) (P<0.0001 for each) albeit significantly lower levels compared with those in patients with pneumonia (n = 72) (P<0.0001 for each) or COPD (n = 72) (P<0.0001, P<0.0001, P = 0.0016, respectively). After 6 months of treatment, the levels of SAA and PROZ were significantly increased (P = 0.022, P<0.0001, respectively), whereas the level of C4BPB was significantly decreased (P = 0.0038) in treated TB cases (n = 72). Clinical analysis showed that there were significant differences in blood clotting and lipid indices in patients with TB compared with healthy controls, patients with pneumonia or COPD, and treated TB cases (P<0.05). Correlation analysis revealed significant correlations between PROZ and INR (rs = 0.414, P = 0.044), and between C4BPB and FIB (rs = 0.617, P = 0.0002) in patients with TB. Receiver operating characteristic curve analysis revealed that the area under the curve value of the diagnostic model combining SAA, PROZ, and C4BPB to discriminate the TB group from the healthy control, pneumonia, COPD, and cured TB groups was 0.972, 0.928, 0.957, and 0.969, respectively. Together, these results suggested that SAA, PROZ, and C4BPB may serve as new potential biomarkers for TB. Our study may thus provide experimental data for the differential diagnosis of TB.

Expression of a serine protease gene prC is up-regulated by oxidative stress in the fungus Clonostachys rosea: implications for fungal survival.

BACKGROUND: Soil fungi face a variety of environmental stresses such as UV light, high temperature, and heavy metals. Adaptation of gene expression through transcriptional regulation is a key mechanism in fungal response to environmental stress. In Saccharomyces cerevisiae, the transcription factors Msn2/4 induce stress-mediated gene expression by binding to the stress response element. Previous studies have demonstrated that the expression of extracellular proteases is up-regulated in response to heat shock in fungi. However, the physiological significance of regulation of these extracellular proteases by heat shock remains unclear. The nematophagous fungus Clonostachys rosea can secret an extracellular serine protease PrC during the infection of nematodes. Since the promoter of prC has three copies of the stress response element, we investigated the effect of environmental stress on the expression of prC. METHODOLOGY/PRINCIPAL FINDINGS: Our results demonstrated that the expression of prC was up-regulated by oxidants (H(2)O(2) or menadione) and heat shock, most likely through the stress response element. After oxidant treatment or heat shock, the germination of conidia in the wild type strain was significantly higher than that in the prC mutant strain in the presence of nematode cuticle. Interestingly, the addition of nematode cuticle significantly attenuated the production of reactive oxygen species (ROS) induced by oxidants and heat shock in the wild type strain, but not in prC mutant strain. Moreover, low molecule weight (<3 kD) degradation products of nematode cuticle suppressed the inhibitory effect of conidial germination induced by oxidants and heat shock. CONCLUSIONS/SIGNIFICANCE: These results indicate that PrC plays a protective role in oxidative stress in C. rosea. PrC degrades the nematode cuticle to produce degradation products, which in turn offer a protective effect against oxidative stress by scavenging ROS. Our study reveals a novel strategy for fungi to adapt to environmental stress.

Regulation of subtilisin-like protease prC expression by nematode cuticle in the nematophagous fungus Clonostachys rosea.

Nematophagous fungi have been used as biological control agents against nematodes parasitic to plants and animals. These fungi can secret subtilisin-like extracellular serine proteases during the infection of nematodes. The expression of these subtilisin-like serine proteases is regulated by nitrogen sources, including nematode cuticle. However, the mechanisms underlying the nitrogen sources-induced expression of these serine proteases is not well understood. In this study, we investigated the effect of nitrogen sources on the expression of a subtilisin-like extracellular protease, prC, in the nematophagous fungus Clonostachys rosea. Disruption of prC attenuated infection of the fungus to nematodes, indicating that this gene functions as a virulence factor. The inhibition of basal expression of prC by the preferred nitrogen sources (glutamine, ammonia) occurred at the transcriptional level. In contrast, nematode cuticle induced the expression of prC at the post-transcriptional level. The inducible expression of prC by nematode cuticle was significantly suppressed by glutamine, ammonia and phenylmethylsulfonyl fluoride (an inhibitor of serine protease). Thus, the existence of active PrC, albeit at a low level in the medium, is probably essential for further induction of this gene by nematode cuticle. Moreover, the low molecule weight (< 3 kD) degradation products of nematode cuticle could significantly induce the expression of prC. Ammonia suppresses the virulence of C. rosea against nematodes, probably by inhibiting prC expression. Thus, the nematophagous fungi probably could not function well as biocontrol agents in fields fertilized with a large amount of ammonium salt.

PacC in the nematophagous fungus Clonostachys rosea controls virulence to nematodes.

Nematophagous fungi are commonly used as biological control agents of plant and animal parasitic nematodes. However, relatively little is known of the environmental attributes conferring pathogenicity in these fungi. In this report, we investigated the role of PacC-mediated pH response in the pathogenesis of the nematophagous fungus Clonostachys rosea. We identified a pacC orthologue from this fungus and found that its transcript was elevated in C. rosea during the early stage of its infection of nematode. Disruption of pacC resulted in slowed growth at alkaline pH, altered filamentation, reduced conidiation and attenuated virulence to nematodes. The expression of an extracellular serine protease PrC, a putative virulence factor, was downregulated in the pacC mutants. The PrC transcript levels were significantly higher under alkaline growth conditions than under acidic growth conditions. Promoter activity analysis and electrophoretic mobility shift assay indicated that the regulation of PrC by pH via the PacC pathway occurred at the transcriptional level. In conclusion, PacC functions as a positive regulator of virulence to nematodes in C. rosea.