The CsPbs2-interacting protein oxalate decarboxylase CsOxdC3 modulates morphosporogenesis, virulence, and fungicide resistance in Colletotrichum siamense.

The HOG MAPK pathway mediates diverse cellular and physiological processes, including osmoregulation and fungicide sensitivity, in phytopathogenic fungi. However, the molecular mechanisms underlying HOG MAPK pathway-associated stress homeostasis and pathophysiological developmental events are poorly understood. Here, we demonstrated that the oxalate decarboxylase CsOxdC3 in Colletotrichum siamense interacts with the protein kinase kinase CsPbs2, a component of the HOG MAPK pathway. The expression of the CsOxdC3 gene was significantly suppressed in response to phenylpyrrole and tebuconazole fungicide treatments, while that of CsPbs2 was upregulated by phenylpyrrole and not affected by tebuconazole. We showed that targeted gene deletion of CsOxdC3 suppressed mycelial growth, reduced conidial length, and triggered a marginal reduction in the sporulation characteristics of the ΔCsOxdC3 strains. Interestingly, the ΔCsOxdC3 strain was significantly sensitive to fungicides, including phenylpyrrole and tebuconazole, while the CsPbs2-defective strain was sensitive to tebuconazole but resistant to phenylpyrrole. Additionally, infection assessment revealed a significant reduction in the virulence of the ΔCsOxdC3 strains when inoculated on the leaves of rubber tree (Hevea brasiliensis). From these observations, we inferred that CsOxdC3 crucially modulates HOG MAPK pathway-dependent processes, including morphogenesis, stress homeostasis, fungicide resistance, and virulence, in C. siamense by facilitating direct physical interactions with CsPbs2. This study provides insights into the molecular regulators of the HOG MAPK pathway and underscores the potential of deploying OxdCs as potent targets for developing fungicides.

NADPH Oxidases Play a Role in Pathogenicity via the Regulation of F-Actin Organization in Colletotrichum gloeosporioides.

Multiunit-flavoenzyme NADPH oxidases (NOXs) play multiple roles in living cells via regulating signaling pathways. In several phytopathogenic fungi, NOXs are required for the polarized growth of hyphal tips and pathogenicity to host plants, but the possible mechanisms are still elusive. In our previous study, CgNOXA, CgNOXB, and CgNOXR were identified as components of the NOX complex in Colletotrichum gloeosporioides. The growth and the inoculation assays revealed that CgNOXA/B and CgNOXR regulate vegetative growth and are required for the full pathogenicity of C. gloeosporioides to Hevea leaves. We further demonstrated that the vital roles of CgNOXB and CgNOXR in appressorium formation and the development of invasion hyphae account for their functions in pathogenicity. Moreover, CgNOXB and CgNOXR regulate the production and distribution of ROS in hyphal tips and appressoria, control the specialized remodeling of F-actin in hyphal tips and appressoria, and are involved in fungal cell wall biosynthesis. Taken together, our findings highlight the role of NOXs in fungal pathogenicity through the organization of the actin cytoskeleton.

Discovery of non-squalene triterpenes.

All known triterpenes are generated by triterpene synthases (TrTSs) from squalene or oxidosqualene1. This approach is fundamentally different from the biosynthesis of short-chain (C10-C25) terpenes that are formed from polyisoprenyl diphosphates2-4. In this study, two fungal chimeric class I TrTSs, Talaromyces verruculosus talaropentaene synthase (TvTS) and Macrophomina phaseolina macrophomene synthase (MpMS), were characterized. Both enzymes use dimethylallyl diphosphate and isopentenyl diphosphate or hexaprenyl diphosphate as substrates, representing the first examples, to our knowledge, of non-squalene-dependent triterpene biosynthesis. The cyclization mechanisms of TvTS and MpMS and the absolute configurations of their products were investigated in isotopic labelling experiments. Structural analyses of the terpene cyclase domain of TvTS and full-length MpMS provide detailed insights into their catalytic mechanisms. An AlphaFold2-based screening platform was developed to mine a third TrTS, Colletotrichum gloeosporioides colleterpenol synthase (CgCS). Our findings identify a new enzymatic mechanism for the biosynthesis of triterpenes and enhance understanding of terpene biosynthesis in nature.

Identification of Copper-Containing Oxidoreductases in the Secretomes of Three Colletotrichum Species with a Focus on Copper Radical Oxidases for the Biocatalytic Production of Fatty Aldehydes.

Copper radical alcohol oxidases (CRO-AlcOx), which have been recently discovered among fungal phytopathogens, are attractive for the production of fragrant fatty aldehydes. With the initial objective to investigate the secretion of CRO-AlcOx by natural fungal strains, we undertook time course analyses of the secretomes of three Colletotrichum species (C. graminicola, C. tabacum, and C. destructivum) using proteomics. The addition of a copper-manganese-ethanol mixture in the absence of any plant-biomass mimicking compounds to Colletotrichum cultures unexpectedly induced the secretion of up to 400 proteins, 29 to 52% of which were carbohydrate-active enzymes (CAZymes), including a wide diversity of copper-containing oxidoreductases from the auxiliary activities (AA) class (AA1, AA3, AA5, AA7, AA9, AA11, AA12, AA13, and AA16). Under these specific conditions, while a CRO-glyoxal oxidase from the AA5_1 subfamily was among the most abundantly secreted proteins, the targeted AA5_2 CRO-AlcOx were secreted at lower levels, suggesting heterologous expression as a more promising strategy for CRO-AlcOx production and utilization. C. tabacum and C. destructivum CRO-AlcOx were thus expressed in Pichia pastoris, and their preference toward both aromatic and aliphatic primary alcohols was assessed. The CRO-AlcOx from C. destructivum was further investigated in applied settings, revealing a full conversion of C6 and C8 alcohols into their corresponding fragrant aldehydes. IMPORTANCE In the context of the industrial shift toward greener processes, the biocatalytic production of aldehydes is of utmost interest owing to their importance for their use as flavor and fragrance ingredients. Copper radical alcohol oxidases (CRO-AlcOx) have the potential to become platform enzymes for the oxidation of alcohols to aldehydes. However, the secretion of CRO-AlcOx by natural fungal strains has never been explored, while the use of crude fungal secretomes is an appealing approach for industrial applications to alleviate various costs pertaining to biocatalyst production. While investigating this primary objective, the secretomics studies revealed unexpected results showing that under the oxidative stress conditions we probed, Colletotrichum species can secrete a broad diversity of copper-containing enzymes (laccases, sugar oxidoreductases, and lytic polysaccharide monooxygenases [LPMOs]) usually assigned to "plant cell wall degradation," despite the absence of any plant-biomass mimicking compound. However, in these conditions, only small amounts of CRO-AlcOx were secreted, pointing out recombinant expression as the most promising path for their biocatalytic application.

Analysis of N-glycosylation in fungal l-amino acid oxidases expressed in the methylotrophic yeast Pichia pastoris.

l-amino acid oxidases (LAAOs) catalyze the oxidative deamination of l-amino acids to corresponding α-keto acids. Here, we describe the heterologous expression of four fungal LAAOs in Pichia pastoris. cgLAAO1 from Colletotrichum gloeosporioides and ncLAAO1 from Neurospora crassa were able to convert substrates not recognized by recombinant 9His-hcLAAO4 from the fungus Hebeloma cylindrosporum described earlier thereby broadening the substrate spectrum for potential applications. 9His-frLAAO1 from Fibroporia radiculosa and 9His-laLAAO2 from Laccaria amethystine were obtained only in low amounts. All four enzymes were N-glycosylated. We generated mutants of 9His-hcLAAO4 lacking N-glycosylation sites to further understand the effects of N-glycosylation. All four predicted N-glycosylation sites were glycosylated in 9His-hcLAAO4 expressed in P. pastoris. Enzymatic activity was similar for fully glycosylated 9His-hcLAAO4 and variants without one or all N-glycosylation sites after acid activation of all samples. However, activity without acid treatment was low in a variant without N-glycans. This was caused by the absence of a hypermannosylated N-glycan on asparagine residue N54. The lack of one or all of the other N-glycans was without effect. Our results demonstrate that adoption of a more active conformation requires a specific N-glycosylation during biosynthesis.

Mitogen-activated protein kinase cascade CgSte50-Ste11-Ste7-Mk1 regulates infection-related morphogenesis in the poplar anthracnose fungus Colletotrichum gloeosporioides.

The hemibiotrophic pathogen Colletotrichum gloeosporioides is the causal agent of poplar anthracnose and causes considerable economic losses. This fungus infects its host through a specialized structure called an appressorium. In a previous study, we demonstrated that the mitogen-activated protein kinase (MAPK) CgMk1 plays a critical role in appressorium formation and pathogenicity. In this study, we identified three upstream components of CgMk1, the putative adaptor protein CgSte50, MAPKKK CgSte11, and MAPKK CgSte7, and showed that CgSte50, CgSte11, and CgSte7 positively regulate the phosphorylation of CgMk1. Deletion of CgSte50, CgSte11, and CgSte7 resulted in the loss of appressorium formation, penetration of the cellophane membrane, invasive growth and pathogenicity, similar to the defects observed in the CgMk1 mutant. CgSte50, CgSte11, CgSte7 and CgMk1 were also required for polarity during conidial germination. At the initial stage of appressorium formation, the accumulation of reactive oxygen species (ROS) was altered in the CgSte50, CgSte11, CgSte7 and CgMk1 deletion mutants compared with that in wild type (WT). Furthermore, the CgSte50, CgSte11, CgSte7 and CgMk1 deletion mutants manifested pleiotropic defects during vegetative growth; all mutants exhibited albino colonies, and the aerial hyphae had reduced hydrophobicity. In the mutants, autolysis was detected at the colony edge, and septum formation in the hyphae was elevated compared with that in the WT hyphae. Moreover, deletion of CgSte50, CgSte11, CgSte7 and CgMk1 affected vegetative growth under nitrogen-limiting and osmotic stress conditions. CgSte50, CgSte11, and CgSte7 but not CgMk1 were required for the oxidative stress response. Taken together, these results indicate that the CgMk1 MAPK cascade plays vital roles in various important functions in C. gloeosporioides.

Molecular dynamics investigation of the interaction between Colletotrichum capsici cutinase and berberine suggested a mechanism for reduced enzyme activity.

Berberine is a promising botanical pesticide against fungal plant pathogens. However, whether berberine inhibits the invasion of fungal pathogen across plant surface remains unclear. Here we demonstrated that the enzyme activities of purified cutinase from fungal pathogen Colletotrichum capsici were partially inhibited in presence of berberine toward different substrates. Molecular dynamics simulation results suggested the rigidity of cutinase was decreased with berberine added into the system. Interestingly, aggregations of berberine to the catalytic center of cutinase were observed, and stronger hydrophobic interactions were detected between key residue His 208 and berberine with concentrations of berberine increased. More importantly, this hydrophobic interaction conferred conformational change of the imidazole ring of His 208, which swung out of the catalytic center to an inactive mode. In summary, we provided the molecular mechanism of the effect of berberine on cutinase from C. capsici.

Heterologous expression and biochemical characterization of a thermostable endo-ß-1,4-glucanase from Colletotrichum orchidophilum.

To develop new cellulases for efficient utilization of the lignocellulose, an endoglucanase (CoCel5A) gene from Colletotrichum orchidophilum was synthesized and a recombinant Pichia pastoris GS115/pPIC9K/cocel5A was constructed for secretory expression of CoCel5A. After purification, the protein CoCel5A was biochemically characterized. The endoglucanase CoCel5A exhibited the optimal activity at 55-75 °C and high thermostability (about 85% residual activity) at the temperature of 55 °C after incubation for 3 h. The highest activity of CoCel5A was detected when 100 mM citric acid buffer (pH 4.0-5.0) was used and excellent pH stability (up to 95% residual activity) was observed after incubation in 100 mM citric acid buffer (pH 3.0-6.0) at 4 °C for 24 h. Carboxymethyl cellulose sodium salt (n = approx. 500) (CMC) and ß-D-glucan were the best substrates for CoCel5A among the tested substrates. The kinetic parameters Vmax, Km, and Kcat/Km values against CMC were 290.70 U/mg, 2.65 mg/mL, and 75.67 mL/mg/s, respectively; and 228.31 U/mg, 2.06 mg/mL, and 76.45 mL/mg/s against ß-D-glucan, respectively, suggesting that CoCel5A has high affinity and catalytic efficiency. These properties supported the potential application of CoCel5A in biotechnological and environmental fields.

Threonine synthase CoTHR4 is involved in infection-related morphogenesis during the pre-penetration stage in Colletotrichum orbiculare.

Upon recognition of host plants, Colletotrichum orbiculare, an anthracnose disease fungus of cucurbitaceous plants, initiates morphological differentiation, including conidial germination and appressorium formation on the cuticle layer. The series of infection processes of C. orbiculare requires enormous nutrient and energy, but the surface of the cucurbitaceous hosts is hardly nutrient-rich. Hence, C. orbiculare must exert tight management of its intracellular nutrients in order to properly induce infection-related morphogenesis. Here, we carried out a large-scale insertional mutagenesis screen using Agrobacterium tumefaciens-mediated transformation to identify novel genes involved in the pathogenicity of C. orbiculare and found that CoTHR4-encoded threonine synthase, a homolog of Saccharomyces cerevisiae THR4, is required for pathogenicity and conidiation in C. orbiculare. Threonine supplementation allowed the cothr4 mutant to produce conidia to a level equivalent to that of the wild-type. The conidia produced from the threonine-treated cothr4 mutant failed to germinate in the absence of threonine, but retained the ability to germinate and to form appressoria in the presence of threonine. However, the conidia produced from the threonine-treated cothr4 mutant remained attenuated in pathogenicity on cucumber cotyledons even in the presence of threonine. Cytorrhysis assays revealed that appressoria of the cothr4 mutant induced by exogenous threonine treatment showed low turgor generation. Taken together, these results showed that threonine synthase CoThr4 plays a pivotal role in infection-related morphogenesis during the pre-penetration stage of C. orbiculare.

In vitro toxicity of fungicides with different modes of action to alfalfa anthracnose fungus, Colletotrichum destructivum.

Sensitivity of 24 isolates of Colletotrichum destructivum O'Gara, collected from alfalfa plants in Serbia, to eight selected fungicides, was investigated in this study. Molecular identification and pathogenicity test of isolates tested were also performed. Fungicide sensitivity was evaluated in vitro, using mycelial growth assay method. All isolates exhibited significant pathogenicity, causing necrosis at the alfalfa seedling root tips two days after inoculation. Using the primer pair GSF1-SR1 and by comparing the amplified fragments of the tested isolates with the marker (M), the presence of the amplicon of the expected size of about 900 bp was determined for all isolates. The isolates tested in this study showed different sensitivity towards fungicides in vitro. Mycelial growth was highly inhibited by QoI (quinone outside inhibitors) fungicide pyraclostrobin (mean EC50=0.39 µg mL-1) and by DMI (demethylation-inhibiting) fungicide tebuconazole (mean EC50=0.61 µg mL-1), followed by azoxystrobin (mean EC50=2.83 µg mL-1) and flutriafol (mean EC50=2.11 µg mL-1). Multi-site fungicide chlorothalonil and MBC (methyl benzimidazole carbamate) fungicide thiophanate-methyl evinced moderate inhibition with mean EC50=35.31 and 62.83 µg mL-1, respectively. Thirteen isolates were sensitive to SDHI (succinate dehydrogenase inhibitors) fungicide boscalid and fluxapyroxad, (mean EC50=0.49 and 0.19 µg mL-1, respectively), while the rest of isolates were highly resistant.

Protein extract from Cereus jamacaru (DC.) inhibits Colletotrichum gloeosporioides growth by stimulating ROS generation and promoting severe cell membrane damage.

Mandacaru (Cereus jamacaru DC.), is a cactaceous symbol of caatinga vegetation at Brazilian Northeast region, however, there are no much studies about biochemical properties of this species. Here, the pioneering study brings very relevant data to highlight the importance of research with endemic plants of the caatinga. Afterward, the presence of enzymes such as peroxidase, protease, chitinase, ß-1,3-glucanase, and serine (trypsin) and cysteine (papain) protease inhibitors were evaluated. The peroxidase activity was higher in roots than other tissues. The ß-1,3-glucanase and proteolytic activity were prominent in stem and roots. The chitinase activity and protease inhibitor for both classes analyzed were detected in the stem and fruit peel. Antifungal activity against Colletotrichum gloeosporioides showed the root extract has a promising inhibitory activity on this economical important phytopathogenic fungus. After the contact of the hyphae with root extract increase in membrane permeability, based on Propidium Iodide (PI) uptake, and production of reactive oxygen species (ROS) were detected, compared to negative control. In addition, Scanning Electron Microscopy (SEM) analysis showed morphological damage on hyphae structure indicating that the treatment debilitates either cell membrane or cell wall leading to the cell death C. gloeosporioides.

The histidine kinase slnCl1 of Colletotrichum lindemuthianum as a pathogenicity factor against Phaseolus vulgaris L.

Colletotrichum lindemuthianum, the causal agent of anthracnose, is responsible for significant damage in the common bean (Phaseolus vulgaris L.). Unraveling the genetic mechanisms involved in the plant/pathogen interaction is a powerful approach for devising efficient methods to control this disease. In the present study, we employed the Restriction Enzyme-Mediated Integration (REMI) methodology to identify the gene slnCl1, encoding a histidine kinase protein, as involved in pathogenicity. The mutant strain, MutCl1, generated by REMI, showed an insertion in the slnCl1 gene, deficiency of the production and melanization of appressoria, as well as the absence of pathogenicity on bean leaves when compared with the wild-type strain. The slnCl1 gene encodes a histidine kinase class IV called SlnCl1 showing identity of 97% and 83% with histidine kinases from Colletotrichum orbiculare and Colletotrichum gloesporioides, respectively. RNA interference was used for silencing the histidine kinase gene and confirm slnCl1 as a pathogenicity factor. Furthermore, we identified four major genes involved in the RNA interference-mediated gene silencing in Colletotrichum spp. and demonstrated the functionality of this process in C. lindemuthianum. Silencing of the EGFP reporter gene and slnCl1 were demonstrated using qPCR. This work reports for the first time the isolation and characterization of a HK in C. lindemuthianum and the occurrence of gene silencing mediated by RNA interference in this organism, demonstrating its potential use in the functional characterization of pathogenicity genes.

Acetyl-coenzyme A synthetase gene ChAcs1 is essential for lipid metabolism, carbon utilization and virulence of the hemibiotrophic fungus Colletotrichum higginsianum.

Acetyl-coenzyme A (acetyl-CoA) is a key molecule that participates in many biochemical reactions in amino acid, protein, carbohydrate and lipid metabolism. Here, we genetically dissected the distinct roles of two acetyl-CoA synthetase genes, ChAcs1 and ChAcs2, in the regulation of fermentation, lipid metabolism and virulence of the hemibiotrophic fungus Colletotrichum higginsianum. ChAcs1 and ChAcs2 are both highly expressed during appressorial development and the formation of primary hyphae, and are constitutively expressed in the cytoplasm throughout development. We found that C. higginsianum strains without ChAcs1 were non-viable in the presence of most non-fermentable carbon sources, including acetate, ethanol and acetaldehyde. Deletion of ChAcs1 also led to a decrease in lipid content of mycelia and delayed lipid mobilization in conidia to developing appressoria, which suggested that ChAcs1 contributes to lipid metabolism in C. higginsianum. Furthermore, a ChAcs1 deletion mutant was defective in the switch to invasive growth, which may have been directly responsible for its reduced virulence. Transcriptomic analysis and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) revealed that ChAcs1 can affect the expression of genes involved in virulence and carbon metabolism, and that plant defence genes are up-regulated, all demonstrated during infection by a ChAcs1 deletion mutant. In contrast, deletion of ChAcs2 only conferred a slight delay in lipid mobilization, although it was highly expressed in infection stages. Our studies provide evidence for ChAcs1 as a key regulator governing lipid metabolism, carbon source utilization and virulence of this hemibiotrophic fungus.

An Engineered Alcohol Oxidase for the Oxidation of Primary Alcohols.

Structure-guided directed evolution of choline oxidase has been carried out by using the oxidation of hexan-1-ol to hexanal as the target reaction. A six-amino-acid variant was identified with a 20-fold increased kcat compared to that of the wild-type enzyme. This variant enabled the oxidation of 10 mm hexanol to hexanal in less than 24 h with 100 % conversion. Furthermore, this variant showed a marked increase in thermostability with a corresponding increase in Tm of 20 °C. Improved solvent tolerance was demonstrated with organic solvents including ethyl acetate, heptane and cyclohexane, thereby enabling improved conversions to the aldehyde by up to 30 % above conversion for the solvent-free system. Despite the evolution of choline oxidase towards hexan-1-ol, this new variant also showed increased specific activities (by up to 100-fold) for around 50 primary aliphatic, unsaturated, branched, cyclic, benzylic and halogenated alcohols.

A Clade II-D Fungal Chimeric Diterpene Synthase from Colletotrichum gloeosporioides Produces Dolasta-1(15),8-diene.

Based on a terpenoid overproduction platform in yeast for genome mining, a chimeric diterpene synthase from the endophytic fungus Colletotrichum gloeosporioides ES026 was characterized as the (5R,12R,14S)-dolasta-1(15),8-diene synthase. The absolute configuration was independently verified through the use of enantioselectively deuterated terpene precursors, which unequivocally established the predicted C1-III-IV cyclization mode for this first characterized clade II-D enzyme. Extensive isotopic labeling experiments and isolation of the intermediate (1R)-δ-araneosene supported the proposed cyclization mechanism.

Inherent Resistance to 14α-Demethylation Inhibitor Fungicides in Colletotrichum truncatum Is Likely Linked to CYP51A and/or CYP51B Gene Variants.

Anthracnose disease, caused by Colletotrichum truncatum, affects marketable yield during preharvest production and postharvest storage of fruits and vegetables worldwide. Demethylation inhibitor (DMI) fungicides are among the very few chemical classes of single-site mode of action fungicides that are effective in controlling anthracnose disease. However, some species are inherently resistant to DMIs and more information is needed to understand this phenomenon. Isolates of C. truncatum were collected from the United States and China from peach, soybean, citrus, and begonia and sensitivity to six DMIs (difenoconazole, propiconazole, metconazole, tebuconazole, flutriafol, and fenbuconazole) was determined. Compared with DMI sensitive isolates of C. fructicola, C. siamense, and C. fioriniae (EC50 value ranging from 0.03 to 16.2 µg/ml to six DMIs), C. truncatum and C. nymphaeae were resistant to flutriafol and fenbuconazole (with EC50 values of more 50 µg/ml). Moreover, C. truncatum was resistant to tebuconazole and metconazole (with resistance factors of 27.4 and 96.0) and displayed reduced sensitivity to difenoconazole and propiconazole (with resistance factors of 5.1 and 5.2). Analysis of the Colletotrichum spp. genome revealed two potential DMI targets, CYP51A and CYP51B, that putatively encode P450 sterol 14α-demethylases. Both genes were identified and sequenced from C. truncatum and other species and no correlation between CYP51 gene expression levels and fungicide sensitivity was found. Four amino acid variations L208Y, H238R, S302A, and I366L in CYP51A, and three variations H373 N, M376L, and S511T in CYP51B correlated with the DMI resistance phenotype. CYP51A structure model analysis suggested the four alterations may reduce azole affinity. Likewise, CYP51B structure analysis suggested the H373 N and M376L variants may change the conformation of the DMI binding pocket, thereby causing differential sensitivity to DMI fungicides in C. truncatum.

A halotolerant bifunctional ß-xylosidase/α-l-arabinofuranosidase from Colletotrichum graminicola: Purification and biochemical characterization.

A ß-xylosidase from Colletotrichum graminicola (Bxcg) was purified. The enzyme showed high halotolerance, retaining about 63% of the control activity in the presence of 2.5molL-1 NaCl. The presence of NaCl has not affected the optimum reaction temperature (65°C), but the optimum pH was slightly altered (from 4.5 to 5.0) at high salt concentrations. Bxcg was fully stable at 50°C for 24h and over a wide pH range even in the presence of NaCl. In the absence of salt Bxcg hydrolyzed p-nitrophenyl-ß-d-xylopyranoside with maximum velocity of 348.8±11.5Umg-1 and high catalytic efficiency (1432.7±47.3Lmmol-1s-1). Bxcg revealed to be a bifunctional enzyme with both ß-xylosidase and α-l-arabinofuranosidase activities, and hydrolyzed xylooligosaccharides containing up to six pentose residues. The enzyme showed high synergistic effect (3.1-fold) with an endo-xylanase for the hydrolysis of beechwood xylan, either in the absence or presence of 0.5molL-1 NaCl, and was tolerant to different organic solvents and surfactants. This is the first report of a halotolerant bifunctional ß-xylosidase/α-l-arabinofuranosidase from C. graminicola, and the enzyme showed attractive properties for application in lignocellulose hydrolysis, particularly under high salinity and/or in the presence of residues of pretreatment steps.

Evolutionary Analysis of Pectin Lyases of the Genus Colletotrichum.

Pectin lyases (PNLs) are important enzymes that are involved in plant cell wall degradation during the infection process. Colletotrichum is a diverse genus of fungi, which allows the study of the evolution of PNLs and their possible role in pathogen-host interactions and lifestyle adaptations. The phylogenetic reconstruction of PNLs from Colletotrichum and analysis of selection pressures showed the formation of protein lineages by groups of species with different selection pressures and specific patterns. The analysis of positive selection at individual sites using different methods allowed for the identification of three codons with evidence of positive selection in the oligosaccharide-binding region and two codons on the antiparallel sheet, which may influence the interaction with the substrate. Seven codons on the surface of the protein, mainly in the peripheral helices of the PNLs, could have an important function in evasion of plant defenses, as has been proposed in other enzymes. According to our results, it is possible that events of genetic duplication occurred in ancestral lines, followed by episodes of genetic diversification and gene loss, probably influenced by differences in the composition of the host cell wall. Additionally, different patterns of evolution in Colletotrichum appear to be molded by a strong purifying selection and positive selection episodes that forged the observed evolutionary patterns, possibly influenced by host interaction or substrate specificity. This work represents a starting point for the study of sites that may be important for evasion of plant defenses and biotechnological purposes.

A Novel Colletotrichum graminicola Raffinose Oxidase in the AA5 Family.

We describe here the identification and characterization of a copper radical oxidase from auxiliary activities family 5 (AA5_2) that was distinguished by showing preferential activity toward raffinose. Despite the biotechnological potential of carbohydrate oxidases from family AA5, very few members have been characterized. The gene encoding raffinose oxidase from Colletotrichum graminicola (CgRaOx; EC 1.1.3.-) was identified utilizing a bioinformatics approach based on the known modular structure of a characterized AA5_2 galactose oxidase. CgRaOx was expressed in Pichia pastoris, and the purified enzyme displayed the highest activity on the trisaccharide raffinose, whereas the activity on the disaccharide melibiose was three times lower and more than ten times lower activity was detected on d-galactose at a 300 mM substrate concentration. Thus, the substrate preference of CgRaOx was distinguished clearly from the substrate preferences of the known galactose oxidases. The site of oxidation for raffinose was studied by 1H nuclear magnetic resonance and mass spectrometry, and we confirmed that the hydroxyl group at the C-6 position was oxidized to an aldehyde and that in addition uronic acid was produced as a side product. A new electrospray ionization mass spectrometry method for the identification of C-6 oxidized products was developed, and the formation mechanism of the uronic acid was studied. CgRaOx presented a novel activity pattern in the AA5 family.IMPORTANCE Currently, there are only a few characterized members of the CAZy AA5 protein family. These enzymes are interesting from an application point of view because of their ability to utilize the cheap and abundant oxidant O2 without the requirement of complex cofactors such as FAD or NAD(P). Here, we present the identification and characterization of a novel AA5 member from Colletotrichum graminicola As discussed in the present study, the bioinformatics approach using the modular structure of galactose oxidase was successful in finding a C-6 hydroxyl carbohydrate oxidase having substrate preference for the trisaccharide raffinose. By the discovery of this activity, the diversity of the CAZy AA5 family is increasing.

Expression and functional analysis of the lysine decarboxylase and copper amine oxidase genes from the endophytic fungus Colletotrichum gloeosporioides ES026.

Huperzine A (HupA) isolated from Huperzia serrata is an important compound used to treat Alzheimer's disease (AD). Recently, HupA was reported in various endophytic fungi, with Colletotrichum gloeosporioides ES026 previously isolated from H. serrata shown to produce HupA. In this study, we performed next-generation sequencing and de novo RNA sequencing of C. gloeosporioides ES026 to elucidate the molecular functions, biological processes, and biochemical pathways of these unique sequences. Gene ontology and Kyoto Encyclopedia of Genes and Genomes assignments allowed annotation of lysine decarboxylase (LDC) and copper amine oxidase (CAO) for their conversion of L-lysine to 5-aminopentanal during HupA biosynthesis. Additionally, we constructed a stable, high-yielding HupA-expression system resulting from the overexpression of CgLDC and CgCAO from the HupA-producing endophytic fungus C. gloeosporioides ES026 in Escherichia coli. Quantitative reverse transcription polymerase chain reaction analysis confirmed CgLDC and CgCAO expression, and quantitative determination of HupA levels was assessed by liquid chromatography high-resolution mass spectrometry, which revealed that elevated expression of CgLDC and CgCAO produced higher yields of HupA than those derived from C. gloeosporioides ES026. These results revealed CgLDC and CgCAO involvement in HupA biosynthesis and their key role in regulating HupA content in C. gloeosporioides ES026.