Defence signalling marker gene responses to hormonal elicitation differ between roots and shoots

Abstract

Phytohormones such as jasmonic acid (JA), salicylic acid (SA), ethylene (ET) and abscisic acid (ABA) play a key role in regulation of plant immune responses to different attackers. Extensive research over recent years has led to the identification of molecular markers for specific hormonal-regulated defence pathways. However, most of our current knowledge on the regulation of plant immunity derives from studies focused on above-ground organs, mainly on the model plant Arabidopsis thaliana. Therefore, it is unclear whether the paradigms based on experiments on above-ground organs are entirely transferable to roots. Here, we used the non-model plant Brassica rapa to study the regulation dynamics of hormonal-related marker genes in both roots and shoots. These markers were identified in Arabidopsis shoots after elicitation of the JA-, SA-, ET- or ABA-signalling pathways, and are commonly used to study induced responses. We assessed whether the regulation of those genes by hormonal elicitation differs between roots and shoots. To discern whether the differences in marker gene expression between roots and shoots are related to differences in hormone production or to differential responsiveness, we also measured actual hormone content in the treated tissue after elicitation. Our results show that some of the widely used markers did not show specific responsiveness to single hormone applications in B. rapa. We further found that hormonal elicitation led to different response patterns of the molecular markers in shoots and roots. Our results suggest that the regulation of some hormonal-related marker genes in B. rapa is organ specific and differs from the Arabidopsis-derived paradigms.

Unearthing the Plant Growth-Promoting Traits of Bacillus megaterium RmBm31, an Endophytic Bacterium Isolated From Root Nodules of Retama monosperma

“…This gene expression analysis was performed using a comprehensive set of 33 marker genes for the biosynthesis, transport or signaling pathways of the nine plant hormones (Table S6). Preference were given to marker genes that showed specific responsiveness to single exogenous hormone applications based on previous studies (Nemhauser et al, 2006;Paponov et al, 2008;De Smet et al, 2015;Pandey et al, 2016;Papadopoulou et al, 2018) and according to data in gene expression databases (BAR eFP Browser and Genevestigator).…”

“…auxin and cytokinin perception triple mutants tir1afb2afb3 and cre1-12/ahk2-2tk/ ahk3-3) (Ortíz-Castro et al, 2008;Zamioudis et al, 2013). In recent years, genome-wide gene expression profiling and targeted gene expression analyses with pathway-specific marker genes have emerged as useful complementary or alternative strategies (Papadopoulou et al, 2018) to screen for molecular mechanisms that may be involved in a particular biological process. We chose to apply such strategy by investigating the capacity of RmBm31 to induce transcriptional changes in auxin response/signaling, as well as other phytohormonal pathways in the seedling roots and shoots.…”

Plant Immunity Is Compartmentalized and Specialized in Roots

“…Previous studies performed in roots indicated that PTI includes molecular events such as the production of ROS ( Poncini et al, 2017 ), transcriptional reprogramming ( Boller and Felix, 2009 ; Millet et al, 2010 ), callose deposition ( Millet et al, 2010 ) and modified extensin distribution within the cell wall ( Ribeiro, 2006 ; Wojtasik et al, 2011 ; Plancot et al, 2013 ; Figure 1A ). Phytohormones including salicylic acid (SA), jasmonic acid (JA), and ethylene (ET), are also implicated in root defense against pathogens ( Tytgat et al, 2013 ; Papadopoulou et al, 2018 ). However, the antagonistic interactions of the two hormones JA and SA reported in leaves did not always follow the infection process in, for example, the roots of Arabidopsis thaliana ( Badri et al, 2008 ; Attard et al, 2010 ).…”

A singleton NLR of recent origin causes hybrid necrosis inArabidopsis thaliana

“…Since the F1 hybrid displayed signs of an increased pathogen defense response, we analyzed the expression of a set of marker genes for defense-associated phytohormones such as jasmonic acid (JA), salicylic acid (SA) and ethylene (ET) (Papadopoulou et al 2018), as well as early pathogen response genes induced by both cell surface receptors and NLRs (Ding et al 2020) (Table S3). Genes involved in SA biosynthesis and signaling, such as EDS1, ICS1, EDS5, PAD4, PBS3, CBP60 and FMO1, were strongly overexpressed in F1 hybrid plants, in concordance with the GO analysis, as was the SA-induced camalexin biosynthesis gene CYP71A13.…”