The Botrytis cinerea xylanase Xyn11A contributes to virulence with its necrotizing activity, not with its catalytic activity

Abstract

BackgroundThe Botrytis cinerea xylanase Xyn11A has been previously shown to be required for full virulence of this organism despite its poor contribution to the secreted xylanase activity and the low xylan content of B. cinerea hosts. Intriguingly, xylanases from other fungi have been shown to have the property, independent of the xylan degrading activity, to induce necrosis when applied to plant tissues, so we decided to test the hypothesis that secreted Xyn11A contributes to virulence by promoting the necrosis of the plant tissue surrounding the infection, therefore facilitating the growth of this necrotroph.ResultsWe show here that Xyn11A has necrotizing activity on plants and that this capacity is conserved in site-directed mutants of the protein lacking the catalytic activity. Besides, Xyn11A contributes to the infection process with the necrotizing and not with the xylan hydrolyzing activity, as the catalytically-impaired Xyn11A variants were able to complement the lower virulence of the xyn11A mutant. The necrotizing activity was mapped to a 30-amino acids peptide in the protein surface, and this region was also shown to mediate binding to tobacco spheroplasts by itself.ConclusionsThe main contribution of the xylanase Xyn11A to the infection process of B. cinerea is to induce necrosis of the infected plant tissue. A conserved 30-amino acids region on the enzyme surface, away from the xylanase active site, is responsible for this effect and mediates binding to plant cells.

Plastic Transcriptomes Stabilize Immunity to Pathogen Diversity: The Jasmonic Acid and Salicylic Acid Networks within the Arabidopsis/Botrytis Pathosystem

“…This suggests that this collection of B. cinerea genotypes does not contain large-effect qualitative virulence loci; instead, this generalist uses a highly polygenic virulence architecture (Denby et al, 2004;Finkers et al, 2007b;Rowe and Kliebenstein, 2008;Corwin et al, 2016b;Zhang et al, 2016). This agrees with previous B. cinerea mechanistic studies that identify a large collection of standing genetic variation that controls a wide range of specific virulence mechanisms (Choquer et al, 2007;Rowe and Kliebenstein, 2007;Noda et al, 2010;Rowe et al, 2010;Dalmais et al, 2011;Michielse et al, 2011;Shlezinger et al, 2011;Windram et al, 2012;Pearson and Bailey, 2013;Kumari et al, 2014;An et al, 2015;Atwell et al, 2015;Hevia et al, 2015;Plaza et al, 2015;Schumacher et al, 2015;Zhang et al, 2015a;Corwin et al, 2016aCorwin et al, , 2016bLopezCruz et al, 2017;Zhang et al, 2016). Taken together, this supports the perspective that the Arabidopsis-B.…”

Secretome analysis reveals effector candidates associated with broad host range necrotrophy in the fungal plant pathogen Sclerotinia sclerotiorum

“…SPEP genes for which positive selection has been detected encode cell wall degrading enzymes, including SS1G _ 07749 encoding a putative xylanase. This protein is related to B. cinerea Xyn11 considered as a Pathogen Associated Molecular Pattern (PAMP) [9]. The detection of positive selection in SS1G _ 07749 is therefore consistent with the hypothesis that PAMPs may be characterized by signatures of positive selection in a background of strong negative selection [50].…”

Fungal Endopolygalacturonases Are Recognized as Microbe-Associated Molecular Patterns by the Arabidopsis Receptor-Like Protein RESPONSIVENESS TO BOTRYTIS POLYGALACTURONASES1

“…This result is analogous to observations reported for the Trichoderma spp. EIX and B. cinerea xylanase xyn11A, proteins that are both able to induce a necrotic response independent of their catalytic activity (Enkerli et al, 1999;Furman-Matarasso et al, 1999;Noda et al, 2010). Second, the protein concentrations required for necrosisinducing activity were quite similar for all five PGs tested in this study (approximately 10 mM), in spite of the fact that the enzymes differ markedly in their specific activities (ranging from 20 to 900 units mg 21 for B. cinerea PGs; Kars et al, 2005).…”