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

• Published in: Journal of fungi (Basel) Vol. 7; no. 12; p. 1081
• Main Authors: Moreno-Sánchez, Ismael, Pejenaute-Ochoa, María Dolores, Navarrete, Blanca, Barrales, Ramón R, Ibeas, José I
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 15-12-2021; MDPI
• Subjects: Apoplast; Biodegradation; Cell cycle; Cell walls; Cellulase; Cellulose; Enzymes; Filamentation; Fungal infections; Fungi; Genes; Glycoside hydrolase; High-throughput screening; Hydrolase; Molecular weight; pathogenesis; Pathogens; PCWDE; Pheromones; Plasmids; Polysaccharides; smut fungi; Tumors; Ustilago maydis; Virulence; Xylan; St Louis Missouri; United States > US; pathogenesis; PCWDE; smut fungi
• ISSN: 2309-608X; 2309-608X
• DOI: 10.3390/jof7121081

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
, 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
infection. Here, we characterize the entire
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.