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Front. Plant Sci. | doi: 10.3389/fpls.2018.00409

The apoplastic secretome of Trichoderma virens during interaction with maize roots shows an inhibition of plant defence and scavenging oxidative stress secreted proteins.

 Guillermo Nogueira-López1, David R. Greenwood2,  Martin Middleditch2, Christopher Winefield3, Carla Eaton4, Johanna M. Steyaert5 and  Artemio Mendoza-Mendoza1*
  • 1Bio-Protection Research Centre, Lincoln University, New Zealand
  • 2School of Biological Sciences, University of Auckland, New Zealand
  • 3Wine, Food and Molecular Biosciences, Lincoln University, New Zealand
  • 4Bio-Protection Research Centre and Institute of Fundamental Sciences Massey University, Massey University, New Zealand
  • 5Lincoln Agritech Ltd, Lincoln University, New Zealand

In Nature, almost every plant is colonised by fungi. Trichoderma virens is a biocontrol fungus which has the capacity to behave as an opportunistic plant endophyte. Even though many plants are colonised by this symbiont, the exact mechanisms by which Trichoderma masks its entrance into its plant host remain unknown, but likely involve the secretion of different families of proteins into the apoplast that may play crucial roles in the suppression of plant immune responses. In this study, we studied T. virens colonization of maize roots under hydroponic conditions, evidencing inter and intracellular colonization by the fungus and modifications in root morphology and colouration. Moreover, we show that upon host penetration, T. virens secretes into the apoplast an arsenal of proteins to facilitate inter- and intracellular colonisation of maize root tissues. Using a gel-free shotgun proteomics approach, 95 and 43 secretory proteins were identified from maize and T. virens, respectively. A reduction in the maize secretome (46%) was induced by T. virens, including two major groups, glycosyl hydrolases and peroxidases. Furthermore, T. virens secreted proteins were mainly involved in cell wall hydrolysis, scavenging of reactive oxygen species and secondary metabolism, as well as putative effector-like proteins. Levels of peroxidase activity were reduced in the inoculated roots, suggesting a strategy used by T. virens to manipulate host immune responses. The results provide an insight into the crosstalk in the apoplast which is essential to maintain the T. virens-plant interaction.

Keywords: Peroxidases, Apoplast, Secretome, Trichoderma, roots, endophyte., reactive oxygen species (ROS)

Received: 11 Dec 2017; Accepted: 14 Mar 2018.

Edited by:

Víctor Flors, Jaume I University, Spain

Reviewed by:

Maria J. Pozo, Consejo Superior de Investigaciones Científicas (CSIC), Spain
Tanja Mimmo, Free University of Bozen-Bolzano, Italy  

Copyright: © 2018 Nogueira-López, Greenwood, Middleditch, Winefield, Eaton, Steyaert and Mendoza-Mendoza. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dr. Artemio Mendoza-Mendoza, Lincoln University, Bio-Protection Research Centre, Lincoln, New Zealand,