The Role of Silicon in Anti-herbivore Phytohormonal Signalling
- 1Hawkesbury Institute for the Environment, Western Sydney University, Australia
- 2University of York, United Kingdom
- 3Hawkesbury Institute for the Environment, Western Sydney University, Australia
The role of plant silicon (Si) in the alleviation of abiotic and biotic stress is now widely recognised and researched. Amongst the biotic stresses, Si is known to increase resistance to herbivores through biomechanical and chemical mechanisms, although the latter are indirect and remain poorly characterised. Chemical defences are principally regulated by several anti-herbivore phytohormones. The jasmonic acid (JA) signalling pathway is particularly important and has been linked to Si supplementation, albeit with some contradictory findings. In this Perspectives article, we summarise existing knowledge of how Si affects JA in the context of herbivory and present a conceptual model for the interactions between Si and JA signalling in wounded plants. Further, we use novel information from the model grass Brachypodium distachyon to underpin aspects of this model. We show that Si suppresses reduces JA concentrations in plants subjected to chemical induction (methyl jasmonate; MeJA) and herbivory (Helicoverpa armigera) by 34% and 32%, respectively. Moreover, +Si plants had 13% more leaf macro-hairs than –Si plants. From this study and previous work, our model proposes that Si acts as a physical stimulus in the plant which causes a small, transient increase in JA. When +Si plants are subsequently attacked by herbivores they potentially show a faster induction of JA due to this priming. +Si plants that have already invested in biomechanical defences (e.g. trichomesmacro-hairs), however, have less utility for JA-induced defences and show lower levels of JA-induction overall.
Keywords: allelochemical, Induced defences, insect, Jasmonates, plant defence, silica
Received: 23 May 2019;
Accepted: 15 Aug 2019.
Copyright: © 2019 Hall, Waterman, Vandegeer, Hartley and Johnson. 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(s) 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.
Mr. Jamie M. Waterman, Hawkesbury Institute for the Environment, Western Sydney University, Penrith, 2751, New South Wales, Australia, J.Waterman@westernsydney.edu.au
Dr. Scott N. Johnson, Western Sydney University, Hawkesbury Institute for the Environment, Penrith, 2751, New South Wales, Australia, Scott.Johnson@uws.edu.au