Elicitor induction of defence genes and reduction of bacterial canker in kiwifruit

Abstract

Pseudomonas syringae pv. actinidiae (Psa), which causes bacterial canker, is the most serious global pathogen of kiwifruit. Like most bacterial pathogens, control options are limited, but elicitors can reduce disease significantly, particularly those that induce the salicylic acid (SA) pathway. Acibenzolar-S-methyl (ASM), a SA analogue, is one of the most effective elicitors for Psa control. In this study, real-time PCR (qPCR) was used to measure the expression of 18 putative defence genes in Actinidia chinensis var. chinensis 'Hort16A' in response to Psa and ASM. Application of ASM led to up-regulation of RPM1 interacting protein 4 (RIN4), phenylalanine ammonia lyase (PAL), a hypersensitivity-induced response protein (HIRP), and β-1,3-glucosidase. Expression of PAL and HIRP was further enhanced when elicitor application and Psa-inoculation were combined. Elevated gene expression was correlated with decreased disease expression, and supports the hypothesis that elicitor-treated plants are primed to react more rapidly and/or strongly to pathogens.

Phytohormone and Putative Defense Gene Expression Differentiates the Response of ‘Hayward’ Kiwifruit to Psa and Pfm Infections

“…The basal transcript level in untreated plants was then used as a further reference point for all calculations and is referred to with the value 1. Choice of GoIs was based upon their putative involvement in kiwifruit resistance against other important pests and diseases ( Wurms, 2005 ; Reglinski et al, 2010 ; Wurms et al, 2011 ; Hill et al, 2015 ), as well as preliminary qPCR studies of kiwifruit responses to Psa ( Wurms et al, 2013 ; Cellini et al, 2014 ), and a next generation sequencing study of the ‘Hort16A’/Psa interaction (A. Allan, PFR, New Zealand, unpublished data). Published studies of commonly used markers of hormonal pathways ( Suza and Staswick, 2008 ; Ding et al, 2009 ; Pieterse et al, 2009 , 2012 ; Sanchez-Vallet et al, 2012 ; Wasternack and Hause, 2013 ; Meesters et al, 2014 ), and defense responses of other plants, most often Arabidopsis thaliana , to Pseudomonas syringae were also used to select GoI ( Lorenzo et al, 2004 ; Pré et al, 2008 ; Liu et al, 2009 ).…”

What Slows Down Phytoplasma Proliferation? Speculations on the Involvement of AtSEOR2 Protein in Plant Defence Signalling

“…This speculation implies that, thanks to AtSEOR2 priming effect, Atseor1ko plants can rapidly recruit (or have already activated) many defence responses against phytoplasmas during the early stages of infection and thus can limit pathogen propagation (Figure 3). Since the involvement in the RIN4 signal transduction pathways of molecules other than pathogen effectors has been demonstrated 38,39 , free AtSEOR2 protein may exert a similar effect. To test if an interaction between AtRIN4 and AtSEOR2 protein limits pathogen spread, it would be interesting to quantify the pathogen presence in wild-type and Atseor1ko plants infected with Pseudomonas syringae, a pathogen known to be affected by RIN4-mediated plant response.…”

Early Pathogen Recognition and Antioxidant System Activation Contributes to Actinidia arguta Tolerance Against Pseudomonas syringae Pathovars actinidiae and actinidifoliorum

“…Plant defense against pathogens is also associated with molecular networks based on the activity of reactive oxygen species (ROS), such as superoxide (O 2 − ) and hydrogen peroxide (H 2 O 2 ), and phytohormone signalling, including jasmonic acid (JA) and salicylic acid (SA) (Petriccione et al, 2014;Wurms et al, 2017b). Increased production of ROS during stress, in particular, may pose a threat to cell homeostasis due to subsequent lipid peroxidation, protein oxidation, nucleic acid damage, and enzyme inhibition, ultimately resulting in cell death (Sharma et al, 2012).…”