The xylanase inhibitor TAXI-III counteracts the necrotic activity of a Fusarium graminearum xylanase in vitro and in durum wheat transgenic plants.

The xylanase inhibitor TAXI-III has been proven to delay Fusarium head blight (FHB) symptoms caused by Fusarium graminearum in transgenic durum wheat plants. To elucidate the molecular mechanism underlying the capacity of the TAXI-III transgenic plants to limit FHB symptoms, we treated wheat tissues with the xylanase FGSG_03624, hitherto shown to induce cell death and hydrogen peroxide accumulation. Experiments performed on lemmas of flowering wheat spikes and wheat cell suspension cultures demonstrated that pre-incubation of xylanase FGSG_03624 with TAXI-III significantly decreased cell death. Most interestingly, a reduced cell death relative to control non-transgenic plants was also obtained by treating, with the same xylanase, lemmas of TAXI-III transgenic plants. Molecular modelling studies predicted an interaction between the TAXI-III residue H395 and residues E122 and E214 belonging to the active site of xylanase FGSG_03624. These results provide, for the first time, clear indications in vitro and in planta that a xylanase inhibitor can prevent the necrotic activity of a xylanase, and suggest that the reduced FHB symptoms on transgenic TAXI-III plants may be a result not only of the direct inhibition of xylanase activity secreted by the pathogen, but also of the capacity of TAXI-III to avoid host cell death.

[1]  D. Roby,et al.  Secretome analysis reveals effector candidates associated with broad host range necrotrophy in the fungal plant pathogen Sclerotinia sclerotiorum , 2014, BMC Genomics.

[2]  Y. Lou,et al.  Overexpression of a Xylanase Inhibitor Gene, OsHI-XIP, Enhances Resistance in Rice to Herbivores , 2014, Plant Molecular Biology Reporter.

[3]  S. Masci,et al.  Constitutive expression of the xylanase inhibitor TAXI-III delays Fusarium head blight symptoms in durum wheat transgenic plants. , 2013, Molecular plant-microbe interactions : MPMI.

[4]  R. D'Ovidio,et al.  A Fusarium graminearum xylanase expressed during wheat infection is a necrotizing factor but is not essential for virulence. , 2013, Plant physiology and biochemistry : PPB.

[5]  D. Hegedus,et al.  Brassica napus polygalacturonase inhibitor proteins inhibit Sclerotinia sclerotiorum polygalacturonase enzymatic and necrotizing activities and delay symptoms in transgenic plants. , 2013, Canadian journal of microbiology.

[6]  Xiaodong Wang,et al.  TaMCA4, a novel wheat metacaspase gene functions in programmed cell death induced by the fungal pathogen Puccinia striiformis f. sp. tritici. , 2012, Molecular plant-microbe interactions : MPMI.

[7]  T. Friesen,et al.  Molecular characterization and genomic mapping of the pathogenesis-related protein 1 (PR-1) gene family in hexaploid wheat (Triticum aestivum L.) , 2011, Molecular Genetics and Genomics.

[8]  J. Delcour,et al.  Accumulated Evidence Substantiates a Role for Three Classes of Wheat Xylanase Inhibitors in Plant Defense , 2010 .

[9]  Celedonio González,et al.  The Botrytis cinerea xylanase Xyn11A contributes to virulence with its necrotizing activity, not with its catalytic activity , 2010, BMC Plant Biology.

[10]  Kurt Gebruers,et al.  Identification of structural determinants for inhibition strength and specificity of wheat xylanase inhibitors TAXI‐IA and TAXI‐IIA , 2009, The FEBS journal.

[11]  A. Powell,et al.  Strangers in the matrix: plant cell walls and pathogen susceptibility. , 2008, Trends in plant science.

[12]  P. Labute.  proteins STRUCTURE O FUNCTION O BIOINFORMATICS Protonate3D: Assignment of ionization , 2013 .

[13]  G. Volckaert,et al.  TLXI, a novel type of xylanase inhibitor from wheat (Triticum aestivum) belonging to the thaumatin family. , 2007, The Biochemical journal.

[14]  V. Hornak,et al.  Comparison of multiple Amber force fields and development of improved protein backbone parameters , 2006, Proteins.

[15]  M. Iriti,et al.  Cell death-mediated antiviral effect of chitosan in tobacco. , 2006, Plant physiology and biochemistry : PPB.

[16]  M. Iriti,et al.  Cell death behind invisible symptoms: early diagnosis of ozone injury , 2005, Biologia Plantarum.

[17]  A. Laroche,et al.  Inducers of resistance reduce common bunt infection in wheat seedlings while differentially regulating defence-gene expression , 2005 .

[18]  L. Sella,et al.  An endopolygalacturonase from Sclerotinia sclerotiorum induces calcium-mediated signaling and programmed cell death in soybean cells. , 2005, Molecular plant-microbe interactions : MPMI.

[19]  M. Kimura,et al.  New TAXI-type xylanase inhibitor genes are inducible by pathogens and wounding in hexaploid wheat. , 2004, Plant & cell physiology.

[20]  A. Avni,et al.  The Receptor for the Fungal Elicitor Ethylene-Inducing Xylanase Is a Member of a Resistance-Like Gene Family in Tomato , 2004, The Plant Cell Online.

[21]  J. Gershoni,et al.  Identification of an essential component of the elicitation active site of the EIX protein elicitor. , 2002, The Plant journal : for cell and molecular biology.

[22]  Thomas D. Schmittgen,et al.  Analysis of relative gene expression data using real-time quantitative PCR and the 2(-Delta Delta C(T)) Method. , 2001, Methods.

[23]  A. Levine,et al.  The hypersensitive response facilitates plant infection by the necrotrophic pathogen Botrytis cinerea , 2000, Current Biology.

[24]  T. Boller,et al.  The enzymatic activity of fungal xylanase is not necessary for its elicitor activity. , 1999, Plant physiology.

[25]  A. Avni,et al.  A point mutation in the ethylene-inducing xylanase elicitor inhibits the beta-1-4-endoxylanase activity but not the elicitation activity. , 1999, Plant physiology.

[26]  J. Delcour,et al.  Triticum aestivum xylanase inhibitor (TAXI), a new class of enzyme inhibitor affecting breadmaking performance , 1999 .

[27]  G. Williamson,et al.  A novel class of protein from wheat which inhibits xylanases. , 1999, The Biochemical journal.

[28]  J. Anderson,et al.  The Elicitation of Ethylene Biosynthesis by a Trichoderma Xylanase Is Not Related to the Cell Wall Degradation Activity of the Enzyme , 1993, Plant physiology.

[29]  J. Zadoks.  A decimal code for the growth stages of cereals , 1974 .

[30]  Jin-Rong Xu,et al.  TaDAD2, a negative regulator of programmed cell death, is important for the interaction between wheat and the stripe rust fungus. , 2011, Molecular plant-microbe interactions : MPMI.

[31]  J. Espino,et al.  The endo-beta-1,4-xylanase xyn11A is required for virulence in Botrytis cinerea. , 2006, Molecular plant-microbe interactions : MPMI.

[32]  R. D'Ovidio,et al.  The role of polygalacturonase-inhibiting proteins (PGIPs) in defense against pathogenic fungi. , 2001, Annual review of phytopathology.