Secretion Of Cell Wall Degrading Enzymes Research Articles

Metabolomic and Transcriptome Analysis of the Inhibitory Effects of Bacillus subtilis Strain Z-14 against Fusarium oxysporum Causing Vascular Wilt Diseases in Cucumber

Controlling cucumber Fusarium wilt caused by Fusarium oxysporum f. sp. cucumerinum (FOC) with Bacillus strains is a hot research topic. However, the molecular mechanism of Bacillus underlying the biocontrol of cucumber wilt is rarely reported. In this study, B. subtilis strain Z-14 showed significant antagonistic activity against FOC, and the control effect reached 88.46% via pot experiment. Microscopic observations showed that strain Z-14 induced the expansion and breakage of FOC hyphae. The cell wall thickness was uneven, and the organelle structure was degraded. The combined analysis of metabolome and transcriptome showed that strain Z-14 inhibited the FOC infection by inhibiting the synthesis of cell wall and cell membrane, energy metabolism, and amino acid synthesis of FOC mycelium, inhibiting the clearance of reactive oxygen species (ROS) and the secretion of cell wall-degrading enzymes (CWDEs), thereby affecting mitogen-activated protein kinase (MAPK) signal transduction and inhibiting the transport function.

Recent Advances in the Study of the Plant Pathogenic Fungus Botrytis cinerea and its Interaction with the Environment.

The primary contact between the fungal phytopathogen Botrytis cinerea and its host takes place at the cell surface of both organisms. The fungal cell wall is generally composed of an inner skeletal layer consisting of various polysaccharides surrounded by a layer of glycoproteins. Some of these glycoproteins have structural or enzymatic functions, or are involved in conidial adhesion. After landing on the host surface and sensing appropriate signals, B. cinerea conidia produce a germ tube and secrete phytotoxic fungal metabolites and cell wall-degrading enzymes (CWDEs), facilitating host penetration. In fact, 118 genes encoding putative Carbohydrate-Active Enzymes (CAZymes) have been identified in the B. cinerea genome. This large enzymatic repertoire could explain, at least in part, the ability of B. cinerea to infect a vast number of plant species. In recent years, several genes and signaling factors have been identified as playing key roles in pathogenesis, particularly in appressorium formation and penetration. These include the NOX Complex, MAPK cascades, heterotrimeric G proteins, histidine kinases and cAMP signaling pathways. Some of these pathways could also be responsible for controlling the expression and secretion of CWDEs and/or secondary metabolites during infection. Herein, putative virulence factors that are linked to the cell wall, as well as recentlydescribed genes and components that allow the sensing of environmental cues, are highlighted.

Inhibitory effects of sodium silicate on the fungal growth and secretion of cell wall‐degrading enzymes by Trichothecium roseum

AbstractTrichothecium roseum causes decay in muskmelons, apples, tomatoes and mangoes, which leads to economic losses. In this study, we investigated the effect of sodium silicate on the growth of T. roseum and the cell wall‐degrading enzymes (CWDEs) secreted by the hyphae. The results indicated that sodium silicate significantly inhibited mycelial growth and spore germination of T. roseum. The sodium silicate treatment also retarded the secretion of several CWDEs, including pectate lyase (PL), polygalacturonic acid transeliminase (PGTE), pectin methyltranseliminase (PMTE), pectin methylgalacturonase (PMG), polygalacturonase (PG), cellulase (Cx) and β‐glucosidase. These results suggest that sodium silicate exerts its effects on T. roseum through direct inhibition of its growth and secretion of CWDEs.

Characterization of the early response of the orchid, Phalaenopsis amabilis, to Erwinia chrysanthemi infection using expression profiling

Erwinia chrysanthemi is a devastating bacterial pathogen in Phalaenopsis amabilis and causes soft-rotting disease by secretion of cell wall-degrading enzymes. However, the molecular mechanisms underlying the interaction of P. amabilis with E. chrysanthemi remain elusive. In this study, early molecular events of the plant in response to the pathogen attack were investigated. The alteration in reactive oxygen species accumulation and peroxidase activity occurred at the site of infection. Subsequently, a systematic sequencing of expressed sequence tags (ESTs) using suppression subtractive hybridization (SSH) was performed to obtain the first global picture of the assembly of genes involved in the pathogenesis. The majority of the SSH clones showed a high identity with genes coding for proteins that have known roles in redox homeostasis, responses to pathogens and metabolism. A notable number of the SSH clones were those encoding WRKY, MYB and basic leucine zipper transcription factors, indicating the stimulation of intracellular signal transduction. An orchid gene encoding trans-2-enoyl-CoA reductase (ECR) was the most abundant transcripts in the EST library. ECR is an enzyme catalyzing the very long chain fatty acids (VLCFAs) biosynthesis, and the full-length cDNA of the ECR gene (PaECR1) was obtained. Functional analysis of PaECR1 was conducted by virus-induced gene silencing to knock down the gene expression in P. amabilis. The PaECR1-silenced plants were more susceptible to E. chrysanthemi infection, implying potential roles for VLCFAs in the pathogenesis. In summary, the pathogen-responsive gene expression profiles facilitated a more comprehensive view of the molecular events that underlie this economically important plant-pathogen interaction.

An N-acetyl-β- d-glucosaminidase gene, cr-nag1, from the biocontrol agent Clonostachys rosea is up-regulated in antagonistic interactions with Fusarium culmorum

Clonostachys rosea is a widely distributed fungus that often acts as a parasite on other soil fungi. This fungus has also been reported as a potential parasite against nematodes and insects. The antagonistic activity is thought to be correlated with the secretion of cell wall-degrading enzymes, including chitinases. In this work, we identified and characterized an N-acetyl-β- d-glucosaminidase-encoding gene, cr-nag1, belonging to glycosyl hydrolase family 20, from the C. rosea strain IK726 using a degenerated primer strategy designed from conserved motifs. The complete gene, including its promoter region, was obtained by genomic walking. Southern analysis showed that cr-nag1 is present as a single copy gene in C. rosea. Phylogenetically, cr-nag1 showed the highest similarity to N-acetyl-β- d-glucosaminidase genes from other mycoparasitic fungi. Enzymatic assays and RT-PCR showed that the NAGase activity of C. rosea is specifically repressed in medium containing a high glucose content and is expressed in media containing chitin or Fusarium culmorum cell walls as sole carbon sources. Macroscopic and microscopic observations indicated that the mycelial growth of F. culmorum and Pythium ultimum were inhibited during interactions with C. rosea. High expression of cr-nag1 was found in interactions between C. rosea and F. culmorum, whereas the expression of cr-nag1 in interactions between C. rosea and P. ultimum was similar to the control. This indicates that although C. rosea secretes chitin-hydrolysing agents in order to target the cell wall of F. culmorum, it seems to use another strategy for controlling the development of the oomycete P. ultimum.

The Gpmk1 MAP kinase of Fusarium graminearum regulates the induction of specific secreted enzymes

Recently, we described Gpmk1 MAP kinase-disruption mutants of Fusarium graminearum that were fully viable in vitro, but had completely lost their ability to infect wheat. As cell wall-degrading enzymes are postulated to participate in the infection process of F. graminearum, these MAP kinase-disruption mutants were analysed for their ability to produce cell wall-degrading enzymes in vitro and compared with the wild-type strain. The gpmk1 disruption had no effect on the production of pectinolytic or amylolytic enzymes. However, Gpmk1 regulates the early induction of extracellular endoglucanase, xylanolytic, and proteolytic activities. Furthermore, the MAP kinase was responsible for the overall induction of secreted lipolytic activities. Since the disruption of the Gpmk1 MAP kinase leads to an apathogenic phenotype, these results suggest that the infection process of F. graminearum depends on the secretion of cell wall-degrading enzymes, particularly during the early infection stage. Finally, this work provides the first detailed analysis of the apathogenic phenotype of the F. graminearum Gpmk1 mutants.

Interaction of ammonium, glucose, and chitin regulates the expression of cell wall-degrading enzymes in Trichoderma atroviride strain P1.

Chitinolytic and glucanolytic fungal cell wall-degrading enzymes have been suggested to be primary determinants of biocontrol by Trichoderma spp. We examined the effects of ammonium, glucose, chitin, and chito-oligomers on transcription of specific genes and secretion of fungal cell wall-degrading enzymes. The genes ech42, nag1, and gluc78 were examined, as were the enzymes they encode (endochitinase CHIT42, N-acetylhexosaminidase CHIT73, and glucan exo-1,3-beta-glucanase GLUC78, respectively). gluc78 could be induced by nitrogen starvation alone, while both ech42 and nag1 required nitrogen starvation and the presence of chitin for induction. Starvation for both ammonium and glucose resulted in very early expression and secretion of all cell wall-degrading enzymes examined. In the presence of low levels of ammonium (10 mM), both chito-oligomers and chitin triggered CHIT42 and CHIT40 (chitobiosidase) production. CHIT73 secretion occurred in the presence of N-acetylglucosamine and chito-oligomers, while chitin was less effective. The presence of different chito-oligomers resulted in secretion of specific N-acetylhexosaminidases, of which CHIT73 is one. Our results indicate that the expression and secretion of cell wall-degrading enzymes is nitrogen repressed, that effects of carbon and nitrogen nutrition are interactive, and that especially for chitinolytic enzymes, the inductive effect of chitin is altered by the level of ammonium or glucose in the medium.