Abstract
Plants have co-evolved with a diverse array of pathogens and insect herbivores and so have evolved an extensive repertoire of constitutive and induced defence mechanisms activated through complex signalling pathways. OXI1 kinase is required for activation of mitogen-activated protein kinases (MAPKs) and is an essential part of the signal transduction pathway linking oxidative burst signals to diverse downstream responses. Furthermore, changes in the levels of OXI1 appear to be crucial for appropriate signalling. Callose deposition also plays a key role in defence. Here we demonstrate, for the first time, that OXI1 plays an important role in defence against aphids. The Arabidopsis mutant, oxi1-2, showed significant resistance both in terms of population build-up (p < 0.001) and the rate of build-up (p < 0.001). Arabidopsis mutants for β-1,3-glucanase, gns2 and gns3, showed partial aphid resistance, significantly delaying developmental rate, taking two-fold longer to reach adulthood. Whilst β-1,3-glucanase genes GNS1, GNS2, GNS3 and GNS5 were not induced in oxi1-2 in response to aphid feeding, GNS2 was expressed to high levels in the corresponding WT (Col-0) in response to aphid feeding. Callose synthase GSL5 was up-regulated in oxi1-2 in response to aphids. The results suggest that resistance in oxi1-2 mutants is through induction of callose deposition via MAPKs resulting in ROS induction as an early response. Furthermore, the results suggest that the β-1,3-glucanase genes, especially GNS2, play an important role in host plant susceptibility to aphids. Better understanding of signalling cascades underpinning tolerance to biotic stress will help inform future breeding programmes for enhancing crop resilience.
Highlights
Aphids are economically important pests globally causing extensive crop damage both as a result of nutrient abstraction, but, more importantly as disease vectors
The potential roles of oxidative signal inducible 1 (OXI1) kinases, b-1,3-glucanase (GNS) and callose synthase (GSL), and their interaction in enhancing resistance to aphids, was investigated in the present study using a range of Arabidopsis mutants
Bioassay results showed that oxi1-2 significantly (p \ 0.001) reduced the numbers of aphids produced, delaying both the developmental period and reproductive peak, reducing population build-up compared to the corresponding wild type (Col-0; Fig. 1a)
Summary
Aphids are economically important pests globally causing extensive crop damage both as a result of nutrient abstraction, but, more importantly as disease vectors. The other involves recognition of aphid-damaged tissue leading to changes in plant chemistry, followed by the production of signalling molecules that trigger a general stress response, similar to the basal plant defence to pathogens (Smith and Boyko 2007). The relative expression of GSL1 in the WT Ws behaved differently to WT Col-0 in that aphid feeding overall caused down regulation of this gene (Fig. 4a). In both the Ws and the null mutant oxi, aphid feeding caused highly significant (p \ 0.001) down regulation of expression of GSL5 over the 48 h time period, and was greatest in oxi h post infestation (Fig. 4b).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
