Cell wall-degrading enzymes of Didymella bryoniae in relation to fungal growth and virulence in cantaloupe fruit

Abstract

Didymella bryoniae is an important pathogen of cucurbits worldwide. Virulence factors of D. bryoniae were investigated in regard to fungal growth and the production of cell wall-degrading enzymes, polygalacturonase (PG), pectate lyase (PL), pectin lyase (PNL), β-galactosidase (β-Gal) and cellulase (Cx). Virulence levels of five D. bryoniae isolates were determined by the severity of inoculated cantaloupe fruit decay. The highly virulent isolates had more mycelial growth than the moderately virulent isolates in different media. PG activities produced by the highly virulent isolates in shake cultures and in decayed fruit were greater than those of the moderately virulent isolates. PNL, but not PL, in decayed fruit was higher with the highly virulent isolates compared to the moderately virulent ones. The highly virulent isolates showed higher Cx activity than the moderately virulent ones in decayed fruit and in fruit tissue shake culture. β-Gal activities of the highly virulent isolates in pectin shake culture and in decayed fruit were greater than those of the two moderately virulent isolates although fruit also produced β-Gal. Protein analysis showed two fungal β-Gal isozymes in decayed fruit compared to those of healthy fruit. Correlation analysis indicated that the activities of PG, PNL, β-Gal and Cx in cultures and in decayed fruit positively correlated with fungal growth and fruit decay severity. The results of this study suggest that PG, PNL, β-Gal, and Cx appear to be virulence factors of D. bryoniae in cantaloupe decay with PG and β-Gal as the most predominant fruit decay enzymes.

Cell-wall-degrading enzymes produced in vitro and in vivo byRhizoctonia solani, the causative fungus of peanut sheath blight

“…As determinants of the fungal pathogenicity complex, CWDEs may be important to fungi not only for penetration and hyphal branching inside the plant tissue, but also for releasing nutrients from the wall polysaccharides that are necessary for fungal growth ( De Lorenzo et al, 1997 ). Correlation has been confirmed between the levels of CWDE activity and the degree of pathogenesis ( Jia et al, 2009 ; Zhang, Bruton & Biles, 2014 ; Zhou et al, 2016 ; Gawade et al, 2017 ). It has been demonstrated histochemically and histopathologically that the disintegration and change of plant cell walls is due to CWDEs ( Weinhold & Motta, 1973 ; Fehrmann & Mendgen, 1975 ; Wanjiru, Kang & Buchenauer, 2002 ; Kang et al, 2007 ).…”

“…Most plant fungal pathogens produce a wide range of cell-wall-degrading enzymes (CWDEs) ( Zhang et al, 1999 ; Lalaoui et al, 2000 ; Gao et al, 2000 ; Brien & Zamani, 2003 ; Yang et al, 2012b ; Li et al, 2012 ; Zhao et al, 2014 ; Zhang, Bruton & Biles, 2014 ; Amit et al, 2014 ). As determinants of the fungal pathogenicity complex, CWDEs may be important to fungi not only for penetration and hyphal branching inside the plant tissue, but also for releasing nutrients from the wall polysaccharides that are necessary for fungal growth ( De Lorenzo et al, 1997 ).…”

“…Polygalacturonase (PG) and polymethyl-galacturonase (PMG), respectively, break down pectate and pectin, by hydrolysis; they cleave the α-(1,4)-glycosidic bonds in the d -galacturonic acid moieties of the pectic substances with the introduction of water across the oxygen bridge. It has been demonstrated that the ability of pathogenic fungi to produce large quantities of PG in culture and in inoculated tissue is correlated with their virulence ( Lalaoui et al, 2000 ; Douaiher et al, 2007b ; Zhang, Bruton & Biles, 2014 ; Zhang et al, 1999 ; Gawade et al, 2017 ). PMG also shows high activity in culture and in host tissue inoculated with many fungal pathogens and has been determined to be a virulence factor ( Gao et al, 2000 ; Li et al, 2003 , 2012 ; Chen et al, 2006 ; Dong et al, 2010 ; Yang et al, 2012b ; Zhou et al, 2016 ).…”

“…The degradation of the plant cell wall component cellulose in the process of infection is due to the activity of Cxs produced by the pathogen. Cxs are a group of enzymes including endoglucanase (Cx; EC 3.2.1.4), cellobiohydrolase (C 1 ; EC 3.2.1.91) and β-glucosidase (EC 3.2.1.21) ( Sipos et al, 2010 ; Zhang, Bruton & Biles, 2014 ). Cx degrades cellulose to cellobiose and is related to the virulence of pathogens ( Ikotun, 1984 ; Lalaoui et al, 2000 ; Yang et al, 2012b ; Zhao et al, 2014 ; Zhang, Bruton & Biles, 2014 ; Zhou et al, 2016 ).…”

Peer Review #1 of "Insight into plant cell wall degradation and pathogenesis of Ganoderma boninense via comparative genome analysis (v0.1)"

“…Cell wall degrading enzymes (CWDEs) are part of the carbohydrate-active enzymes (CAZymes) produced by plant pathogens for penetrating and degrading the plant cell walls, and these CAZymes have been directly linked to devastating crop diseases (Zhang, Bruton & Biles, 2014;Somai-Jemmali et al, 2017;Gawade et al, 2017). Plant pathogenic fungi, namely among the fungal families of Ascomycota, Basidiomycota, Chytridiomycota, and Zygomycota, have been reported to contain the highest number of CAZymes (Zhao et al, 2013;Kubicek, Starr & Glass, 2014).…”