Ustilago maydis Secreted Endo-Xylanases Are Involved in Fungal Filamentation and Proliferation on and Inside Plants

Plant pathogenic fungi must be able to degrade host cell walls in order to penetrate and invade plant tissues. Among the plant cell wall degrading enzymes (PCWDEs) produced, xylanases are of special interest since its degradation target, xylan, is one of the main structural polysaccharides in plant cell walls. In the biotrophic fungus Ustilago maydis, attempts to characterize PCWDEs required for virulence have been unsuccessful, most likely due to functional redundancy. In previous high-throughput screening, we found one xylanase to be important for U. maydis infection. Here, we characterize the entire U. maydis endo-xylanase family, comprising two enzymes from the glycoside hydrolase (GH) 10 family, Xyn1 and Xyn2, one from GH11, Xyn11A, and one from GH43, Xyn3. We show that all endo-xylanases except Xyn3 are secreted and involved in infection in a non-redundant manner, suggesting different roles for each xylanase in this process. Taking a closer look inside the plant during the pathogenic process, we observed that all secreted xylanases were necessary for fungal proliferation. Finally, we found that at least Xyn11A accumulated in the apoplast of the infected plant after three days, highlighting the role of these enzymes as important secreted proteins during fungal proliferation inside plant tissues.

Download Full-text

Microbial Endoxylanases: Effective Weapons to Breach the Plant Cell-Wall Barrier or, Rather, Triggers of Plant Defense Systems?

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-19-1072 ◽

2006 ◽

Vol 19 (10) ◽

pp. 1072-1081 ◽

Cited By ~ 80

Author(s):

Tim Beliën ◽

Steven Van Campenhout ◽

Johan Robben ◽

Guido Volckaert

Keyword(s):

Cell Wall ◽

Plant Defense ◽

Plant Cell ◽

Cell Walls ◽

Defense Mechanisms ◽

Plant Cell Wall ◽

Cell Wall Degrading Enzymes ◽

Defense Systems ◽

Xylanase Inhibitor

Endo-β-1,4-xylanases (EC 3.2.1.8) are key enzymes in the degradation of xylan, the predominant hemicellulose in the cell walls of plants and the second most abundant polysaccharide on earth. A number of endoxylanases are produced by microbial phytopathogens responsible for severe crop losses. These enzymes are considered to play an important role in phytopathogenesis, as they provide essential means to the attacking organism to break through the plant cell wall. Plants have evolved numerous defense mechanisms to protect themselves against invading pathogens, amongst which are proteinaceous inhibitors of cell wall-degrading enzymes. These defense mechanisms are triggered when a pathogen-derived elicitor is recognized by the plant. In this review, the diverse aspects of endoxylanases in promoting virulence and in eliciting plant defense systems are highlighted. Furthermore, the role of the relatively recently discovered cereal endoxylanase inhibitor families TAXI (Triticum aestivum xylanase inhibitor) and XIP (xylanase inhibitor protein) in plant defense is discussed.

Download Full-text

Induction of Fusarium lytic Enzymes by Extracts from Resistant and Susceptible Cultivars of Pea (Pisum sativum L.)

Pathogens ◽

10.3390/pathogens9110976 ◽

2020 ◽

Vol 9 (11) ◽

pp. 976

Author(s):

Lakshmipriya Perincherry ◽

Chaima Ajmi ◽

Souheib Oueslati ◽

Agnieszka Waśkiewicz ◽

Łukasz Stępień

Keyword(s):

Cell Wall ◽

Plant Extracts ◽

Plant Cell Wall ◽

Pathogenic Fungi ◽

Human Beings ◽

Cell Wall Degrading Enzymes ◽

Lytic Enzymes ◽

Mycelium Growth ◽

Oat Bran

Being pathogenic fungi, Fusarium produce various extracellular cell wall-degrading enzymes (CWDEs) that degrade the polysaccharides in the plant cell wall. They also produce mycotoxins that contaminate grains, thereby posing a serious threat to animals and human beings. Exposure to mycotoxins occurs through ingestion of contaminated grains, inhalation and through skin absorption, thereby causing mycotoxicoses. The toxins weaken the host plant, allowing the pathogen to invade successfully, with the efficiency varying from strain to strain and depending on the plant infected. Fusariumoxysporum predominantly produces moniliformin and cyclodepsipeptides, whereas F. proliferatum produces fumonisins. The aim of the study was to understand the role of various substrates and pea plant extracts in inducing the production of CWDEs and mycotoxins. Additionally, to monitor the differences in their levels when susceptible and resistant pea plant extracts were supplemented. The cultures of F. proliferatum and F. oxysporum strains were supplemented with various potential inducers of CWDEs. During the initial days after the addition of substrates, the fungus cocultivated with pea extracts and other carbon substrates showed increased activities of β-glucosidase, xylanase, exo-1,4-glucanase and lipase. The highest inhibition of mycelium growth (57%) was found in the cultures of F. proliferatum strain PEA1 upon the addition of cv. Sokolik extract. The lowest fumonisin content was exhibited by the cultures with the pea extracts and oat bran added, and this can be related to the secondary metabolites and antioxidants present in these substrates.

Download Full-text

The regulatory and transcriptional landscape associated with carbon utilization in a filamentous fungus

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1915611117 ◽

2020 ◽

Vol 117 (11) ◽

pp. 6003-6013 ◽

Cited By ~ 5

Author(s):

Vincent W. Wu ◽

Nils Thieme ◽

Lori B. Huberman ◽

Axel Dietschmann ◽

David J. Kowbel ◽

...

Keyword(s):

Cell Wall ◽

Transcription Factors ◽

Plant Cell ◽

Plant Cell Wall ◽

Plant Biomass ◽

Carbon Sources ◽

Cell Wall Degrading Enzymes ◽

Degrading Enzymes ◽

Genes Encoding

Filamentous fungi, such asNeurospora crassa, are very efficient in deconstructing plant biomass by the secretion of an arsenal of plant cell wall-degrading enzymes, by remodeling metabolism to accommodate production of secreted enzymes, and by enabling transport and intracellular utilization of plant biomass components. Although a number of enzymes and transcriptional regulators involved in plant biomass utilization have been identified, how filamentous fungi sense and integrate nutritional information encoded in the plant cell wall into a regulatory hierarchy for optimal utilization of complex carbon sources is not understood. Here, we performed transcriptional profiling ofN. crassaon 40 different carbon sources, including plant biomass, to provide data on how fungi sense simple to complex carbohydrates. From these data, we identified regulatory factors inN. crassaand characterized one (PDR-2) associated with pectin utilization and one with pectin/hemicellulose utilization (ARA-1). Using in vitro DNA affinity purification sequencing (DAP-seq), we identified direct targets of transcription factors involved in regulating genes encoding plant cell wall-degrading enzymes. In particular, our data clarified the role of the transcription factor VIB-1 in the regulation of genes encoding plant cell wall-degrading enzymes and nutrient scavenging and revealed a major role of the carbon catabolite repressor CRE-1 in regulating the expression of major facilitator transporter genes. These data contribute to a more complete understanding of cross talk between transcription factors and their target genes, which are involved in regulating nutrient sensing and plant biomass utilization on a global level.

Download Full-text

Arsenal of plant cell wall degrading enzymes reflects host preference among plant pathogenic fungi

Biotechnology for Biofuels ◽

10.1186/1754-6834-4-4 ◽

2011 ◽

Vol 4 (1) ◽

pp. 4 ◽

Cited By ~ 137

Author(s):

Brian C King ◽

Katrina D Waxman ◽

Nicholas V Nenni ◽

Larry P Walker ◽

Gary C Bergstrom ◽

...

Keyword(s):

Cell Wall ◽

Plant Cell ◽

Host Preference ◽

Plant Cell Wall ◽

Pathogenic Fungi ◽

Plant Pathogenic Fungi ◽

Cell Wall Degrading Enzymes ◽

Degrading Enzymes

Download Full-text

Comparative Analysis of Herbaceous and Woody Cell Wall Digestibility by Pathogenic Fungi

Molecules ◽

10.3390/molecules26237220 ◽

2021 ◽

Vol 26 (23) ◽

pp. 7220

Author(s):

Yanhua Dou ◽

Yan Yang ◽

Nitesh Kumar Mund ◽

Yanping Wei ◽

Yisong Liu ◽

...

Keyword(s):

Cell Wall ◽

Plant Cell ◽

Fungal Pathogens ◽

Plant Cell Wall ◽

Apple Tree ◽

Plant Biomass ◽

Genomic Analysis ◽

Pathogenic Fungi ◽

Cell Wall Degrading Enzymes ◽

Enzyme Activity Assay

Fungal pathogens have evolved combinations of plant cell-wall-degrading enzymes (PCWDEs) to deconstruct host plant cell walls (PCWs). An understanding of this process is hoped to create a basis for improving plant biomass conversion efficiency into sustainable biofuels and bioproducts. Here, an approach integrating enzyme activity assay, biomass pretreatment, field emission scanning electron microscopy (FESEM), and genomic analysis of PCWDEs were applied to examine digestibility or degradability of selected woody and herbaceous biomass by pathogenic fungi. Preferred hydrolysis of apple tree branch, rapeseed straw, or wheat straw were observed by the apple-tree-specific pathogen Valsa mali, the rapeseed pathogen Sclerotinia sclerotiorum, and the wheat pathogen Rhizoctonia cerealis, respectively. Delignification by peracetic acid (PAA) pretreatment increased PCW digestibility, and the increase was generally more profound with non-host than host PCW substrates. Hemicellulase pretreatment slightly reduced or had no effect on hemicellulose content in the PCW substrates tested; however, the pretreatment significantly changed hydrolytic preferences of the selected pathogens, indicating a role of hemicellulose branching in PCW digestibility. Cellulose organization appears to also impact digestibility of host PCWs, as reflected by differences in cellulose microfibril organization in woody and herbaceous PCWs and variation in cellulose-binding domain organization in cellulases of pathogenic fungi, which is known to influence enzyme access to cellulose. Taken together, this study highlighted the importance of chemical structure of both hemicelluloses and cellulose in host PCW digestibility by fungal pathogens.

Download Full-text

The Essential Role of Plant Cell Wall Degrading Enzymes in the Success of Biorefineries: Current Status and Future Challenges

Biofuels in Brazil ◽

10.1007/978-3-319-05020-1_8 ◽

2014 ◽

pp. 151-172 ◽

Cited By ~ 2

Author(s):

Marcos Henrique Luciano Silveira ◽

Matti Siika-aho ◽

Kristiina Kruus ◽

Leyanis Mesa Garriga ◽

Luiz Pereira Ramos

Keyword(s):

Cell Wall ◽

Plant Cell ◽

Essential Role ◽

Plant Cell Wall ◽

Current Status ◽

Cell Wall Degrading Enzymes ◽

Degrading Enzymes ◽

Future Challenges

Download Full-text

The role of plant cell wall encapsulation and porosity in regulating lipolysis during the digestion of almond seeds

Food & Function ◽

10.1039/c5fo00758e ◽

2016 ◽

Vol 7 (1) ◽

pp. 69-78 ◽

Cited By ~ 39

Author(s):

Myriam M. L. Grundy ◽

Frédéric Carrière ◽

Alan R. Mackie ◽

David A. Gray ◽

Peter J. Butterworth ◽

...

Keyword(s):

Cell Wall ◽

Plant Cell ◽

Cell Walls ◽

Plant Cell Wall ◽

Intact Cell ◽

Lipid Digestion

Intact cell walls of almond prevent lipase penetration thus hindering lipid digestion.

Download Full-text

Xylan decoration patterns and the plant secondary cell wall molecular architecture

Biochemical Society Transactions ◽

10.1042/bst20150183 ◽

2016 ◽

Vol 44 (1) ◽

pp. 74-78 ◽

Cited By ~ 35

Author(s):

Marta Busse-Wicher ◽

Nicholas J. Grantham ◽

Jan J. Lyczakowski ◽

Nino Nikolovski ◽

Paul Dupree

Keyword(s):

Cell Wall ◽

Plant Cell ◽

Cell Walls ◽

Plant Cell Wall ◽

Md Simulations ◽

Cellulose Microfibrils ◽

Molecular Architecture ◽

Cellulose Fibrils ◽

Main Component

The molecular architecture of plant secondary cell walls is still not resolved. There are several proposed structures for cellulose fibrils, the main component of plant cell walls and the conformation of other molecules is even less well known. Glucuronic acid (GlcA) substitution of xylan (GUX) enzymes, in CAZy family glycosyl transferase (GT)8, decorate the xylan backbone with various specific patterns of GlcA. It was recently discovered that dicot xylan has a domain with the side chain decorations distributed on every second unit of the backbone (xylose). If the xylan backbone folds in a similar way to glucan chains in cellulose (2-fold helix), this kind of arrangement may allow the undecorated side of the xylan chain to hydrogen bond with the hydrophilic surface of cellulose microfibrils. MD simulations suggest that such interactions are energetically stable. We discuss the possible role of this xylan decoration pattern in building of the plant cell wall.

Download Full-text

The toughness of plant cell walls

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1995.0074 ◽

1995 ◽

Vol 348 (1325) ◽

pp. 363-372 ◽

Cited By ~ 55

Keyword(s):

Cell Wall ◽

Plant Cell ◽

Cell Walls ◽

Plant Cell Wall ◽

Volume Fraction ◽

Plant Tissues ◽

Individual Plant ◽

Plant Cell Walls ◽

A Value ◽

Cracking Process

All plant tissues and plant-based materials are composites and therefore, during standard fracture mechanics tests, cracks within them tend to arrest and deflect because of crack-stopping mechanisms at cell boundaries or in air-spaces. Due to this change of direction cracks do not cross the toughest structures, frustrating both their measurement and the understanding of the cracking process. Accordingly, there are no accurate values for the toughness of plant cell walls. We have attempted to solve this problem here by driving the crack with blades. We show from cutting experiments on twenty individual plant tissues and plant-based materials that the intrinsic toughness of plant cell wall, independent of cell form, is between 3.4—4.2 kj m -2 ; for any tissue it is directly proportional to the volume fraction that the cell wall occupies. Plastic work, which is dependent on cellular geometry, can increase toughness to a value of at least 30 kj m -2 in woody tissues, but this capacity is probably not linearly related to cell wall volume fraction.

Download Full-text