1,3-ß-d-Glucan synthase of Paracoccidioides brasiliensis: recombinant protein, expression and cytolocalization in the yeast and mycelium phases.

Paracoccidioides brasiliensis is a thermo-dimorphic human pathogenic fungus that in the mycelium phase lives at 23°C in environment and in the yeast phase at 37°C in the host tissues. In P. brasiliensis, the main polymers that compound the cell wall are chitin, 1,3-ß-D-glucan and 1,3-α-glucan. They make a primary barrier responsible for the structural integrity and form of the cell wall. In P. brasiliensis, just one homologue of 1,3-ß-D-glucan synthase gene (PbFKS1) was found. Here, the active recombinant protein (PbFks1pc) containing the catalytic region was obtained in Escherichia coli. In addition, a paradoxical dissociation was detected between the expression of the PbFKS1 transcript and the level of the corresponding protein PbFks1p, which was higher in the yeast phase, versus the amount of 1,3-ß-D-glucan polymer, which was higher in the mycelium phase. Western blot analysis using protein extracts of cellular fractions showed that PbFks1p is present in the membrane-enriched fraction of mycelium and yeast cells and in the cell wall-enriched fractions of yeast cells. Confocal-immunocytolocalization of PbFks1p identified the protein in the apical growing region of the mycelium and distributed on the surface of the yeast cell. Two possible mechanisms could explain the above-mentioned discrepancy between the data: (a) overexpression of Rho1 GTPase as a regulator of 1,3-ß-D-glucan synthase; (b) possible post-translational regulation of PbFks1p in P. brasiliensis isolates.

Insecticidal activity of two proteases against Spodoptera frugiperda larvae infected with recombinant baculoviruses.

BACKGROUND: Baculovirus comprise the largest group of insect viruses most studied worldwide, mainly because they efficiently kill agricultural insect pests. In this study, two recombinant baculoviruses containing the ScathL gene from Sarcophaga peregrina (vSynScathL), and the Keratinase gene from the fungus Aspergillus fumigatus (vSynKerat), were constructed, and their insecticidal properties analysed against Spodoptera frugiperda larvae. RESULTS: Bioassays of third-instar and neonate S. frugiperda larvae with vSynScathL and vSynKerat showed a decrease in the time needed to kill the infected insects when compared to the wild type virus. We have also shown that both recombinants were able to increase phenoloxidase activity in the hemolymph of S. frugiperda larvae. The expression of proteases in infected larvae resulted in destruction of internal tissues late in infection, which could be the reason for the increased viral speed of kill. CONCLUSIONS: Baculoviruses and their recombinant forms constitute viable alternatives to chemical insecticides. Recombinant baculoviruses containing protease genes can be added to the list of engineered baculoviruses with great potential to be used in integrated pest management programs.

Evaluation of holocellulase production by plant-degrading fungi grown on agro-industrial residues.

Agaricus brasiliensis CS1, Pleurotus ostreatus H1 and Aspergillus flavus produced holocellulases when grown in solid and submerged liquid cultures containing agro-industrial residues, including sugar cane bagasse and dirty cotton residue, as substrates. These isolates proved to be efficient producers of holocellulases under the conditions used in this screening. Bromatological analysis of agro-industrial residues showed differences in protein, fiber, hemicellulose, cellulose and lignin content. Maximal holocellulase activity (hemicellulase, cellulase and pectinase) was obtained using solid-state cultivation with 10% substrate concentration. In this case, remarkably high levels of xylanase and polygalacturonase activity (4,008 and 4,548 IU/l, respectively) were produced by A. flavus when grown in media containing corn residue, followed by P. ostreatus H1 with IU/l values of 1,900 and 3,965 when cultivated on 5% and 10% sugar cane bagasse, respectively. A. brasiliensis CS1 showed the highest reducing sugar yield (11.640 mg/ml) when grown on medium containing sugar cane bagasse. A. brasiliensis was also the most efficient producer of protein, except when cultivated on dirty cotton residue, which induced maximal production in A. flavus. Comparison of enzymatic hydrolysis of sugar cane bagasse and dirty cotton residue by crude extracts of A. brasiliensis CS1, P. ostreatus H1 and A. flavus showed that the best reducing sugar yield was achieved using sugar cane bagasse as a substrate.

Involvement of G-alpha protein GNA3 in production of cell wall-degrading enzymes by Trichoderma reesei (Hypocrea jecorina) during mycoparasitism against Pythium ultimum.

The involvement of the G-alpha protein GNA3 in the production of cell wall-degrading enzymes (CWDEs) by Trichoderma reesei during antagonism against Pythium ultimum was investigated. cAMP content was 2.8-fold higher in the T. reesei mutant gna3QL than in the parental TU-6. The gna3QL, like TU-6, inhibited the growth of P. ultimum in dual culture assays. Scanning electron microscopy showed that the gna3QL promoted more morphological alterations of P. ultimum cell wall than TU-6. In general, gna3QL produced higher activities of CWDEs than TU-6. We therefore suggest that CWDEs production during mycoparasitism by T. reesei against P. ultimum may be associated with the level of GNA3 activity.

Purification and characterization of a beta-Glucanase produced by Trichoderma harzianum showing biocontrol potential

A beta-1,3-glucanase was produced by Trichoderma harzianum in cultures containing chitin as the sole substrate. Two proteins showing beta-1,3-glucanase activity were purified to apparent homogeneity by hydrophobic chromatography. The molecular masses of these proteins were 29 and 36 kDa. The 36 kDa protein was further characterized. It was active on a broad pH range, and maximal activity was detected at pH 5.0. The optimum temperature of the 36 kDa beta-1,3-glucanase was 50°C, but the purified enzyme was very sensitive to temperature. It lost about 60 percent or more of the activity after incubation for 30 min at 45, 50 and 60°C. The apparent K M and Vmax for hydrolysis of laminarin at pH 5.0 and 37°C, were 0.099 mg of reducing sugar/mL and 0.3 mg of reducing sugar/min.mL, respectively. The enzyme was insensitive to organic compound and metal ions, except for the ferric ion which inhibited about 100 percent of the original activity at the concentration of 1 mM. In contrast to other hydrolytic enzymes (a chitinase and a protease) produced by the same T. harzianum isolate (1051), the beta-1,3-glucanase showed no effect on the cell wall of the phytopathogenic fungus Crinipellis perniciosa.

Uma beta-1,3-glucanase foi produzida por Trichoderma harzianum em cultura contendo quitina como fonte de carbono. Duas proteínas com atividade de beta-1,3-glucanase foram purificadas através de cromatografia de interação hidrofóbica. As massas moleculares destas proteínas foram de 29 kDa e 36 kDa. A proteína de 36 kDa foi caracterizada quanto à influência das condições de pH e temperatura. A atividade máxima foi encontrada em pH 5,0 e temperatura de 50°C. A proteína purificada mostrou-se muito sensível à temperatura. Aproximadamente 60 por cento da atividade original foi perdida por incubação da proteína a 45°C, 50°C e 60°C, por 30 min. O K M aparente e a Vmax para hidrólise de laminarina em pH 5,0 à 37°C, foram de 0,099 mg de açúcar redutor/mL e 0,3 mg de açúcar redutor/min.mL, respectivamente. Esta enzima mostrou-se insensível a compostos orgânicos e íons metálicos, exceto íon férrico o qual em uma concentração de 1 mM, inibiu em aproximadamente 100 por cento a atividade da enzima. Ao contrário de outras enzimas hidrolíticas (quitinase e protease) produzidas pelo mesmo isolado 1051 de T. harzianum, a beta-1,3-glucanase descrita aqui não afetou a integridade da parede celular do fitopatógeno Crinipellis perniciosa.

Purification and characterization of an alpha-galactosidase from Aspergillus fumigatus

O fungo termofílico Aspergillus fumigatus secreta as enzimas invertase (b-frutofuranosidase) e a-galactosidase (a-D-galactosídeo galactohi-drolase) que estão envolvidas na hidrólise completa dos oligossacarídeos de rafinose. A enzima a-galactosidase foi produzida em meio de cultura do fungo Aspergillus fumigatus crescido por 36 h a 42 °C em meio mineral mínimo contendo os açúcares galactose, ou melibiose, ou rafinose como fontes de carbono. A enzima foi purificada por filtração em gel, seguida por duas cromatografias de troca iônica. A massa molecular da a-galactosidase determinada por SDS-PAGE foi de 54,7 kDa. A atividade máxima da enzima purificada, utilizando o substrato r-nitrofenil-a-D-galactopiranosídeo (rNPGal) foi na faixa de pH entre 4,5 e 5,5 e a 55 °C. A enzima manteve aproximadamente 80% de sua atividade original mesmo após pré-incubação por 90 minutos a 50 °C. O valor de KM para o substrato rNPGal foi 0,3 mM. A enzima foi capaz de hidrolisar melibiose, mas sua atividade foi muito reduzida na presença do substrato rafinose.

Production of hydrolytic enzymes by Trichoderma isolates with antagonistic activity against Crinipellis perniciosa, the causal agent of witches' broom of cocoa

Two isolates of Trichoderma, which reduce the incidence of witches'broom disease caused in cocoa by Crinipellis perniciosa, were evaluated for their potential to produce hydrolases in liquid medium. Very low or no hydrolytic activity was produced in the absence of any substrate. The activities of chitinase, N-acetylglucosaminidase, beta-1,3-glucanase, total cellulase, endoglucanase, aryl- beta-glucosidase, beta-glucosidase, protease and amylase increased dramatically within 72-120 h of growth in the presence of specific substrates. Except for N-acetylglucosaminidase and beta-glucosidase Trichoderma harzianum isolate 1051 produced the largest amounts of hydrolases. The possible involvement of these enzymes in the antagonistic interaction between Trichoderma and C. perniciosa is discussed.

Characterization of a protease produced by a Trichoderma harzianum isolate which controls cocoa plant witches' broom disease.

BACKGROUND: Several Trichoderma strains have been reported to be effective in controlling plant diseases, and the action of fungal hydrolytic enzymes has been considered as the main mechanism involved in the antagonistic process. However, although Trichoderma strains were found to impair development of Crinipellis perniciosa, the causal agent of cocoa plant witches' broom disease, no fungal strain is available for effective control of this disease. We have then undertaken a program of construction of hydrolytic enzyme-overproducing Trichoderma strains aiming improvement of the fungal antagonistic capacity. The protease of an indian Trichoderma isolate showing antagonistic activity against C. perniciosa was purified to homogeneity and characterized for its kinetic properties and action on the phytopathogen cell wall. RESULTS: A protease produced by the Trichoderma harzianum isolate 1051 was purified to homogeneity by precipitation with ammonium sulfate followed by hydrophobic chromatography. The molecular mass of this protease as determined by SDS-polyacrylamide gel electrophoresis was about 18.8 kDa. Its N-terminal amino acid sequence shares no homology with any other protease. The purified enzyme substantially affected the cell wall of the phytopathogen C. perniciosa. Western-blotting analysis showed that the enzyme was present in the culture supernatant 24 h after the Trichoderma started to grow in casein-containing liquid medium. CONCLUSIONS: The capacity of the Trichoderma harzianum protease to hydrolyze the cell wall of C. perniciosa indicates that this enzyme may be actually involved in the antagonistic process between the two fungi. This fact strongly suggest that hydrolytic enzyme over-producing transgenic fungi may show superior biocontrol capacity.

Amylolytic activity of humicola sp

The thermophylic and cellulolytic fungus Humicola sp. secretes amylases in the liquid culture medium. This activity is induced by starch, maltose and cellobiose. Glucose impairs accumlation of amylolitic activity in the culture medium. The enzyme hydrolyzes starch, maltose and pullulan to glucose as the endproduct