Deciphering Molecular Host-Pathogen Interactions During Ramularia Collo-Cygni Infection on Barley

Abstract

Ramularia collo-cygni is the causal agent of Ramularia leaf spot disease (RLS) on barley and became, during the recent decades, an increasing threat for farmers across the world. Here, we analyze morphological, transcriptional, and metabolic responses of two barley cultivars having contrasting tolerance to RLS, when infected by an aggressive or mild R. collo-cygni isolate. We found that fungal biomass in leaves of the two cultivars does not correlate with their tolerance to RLS, and both cultivars displayed cell wall reinforcement at the point of contact with the fungal hyphae. Comparative transcriptome analysis identified that the largest transcriptional differences between cultivars are at the early stages of fungal colonization with differential expression of kinases, calmodulins, and defense proteins. Weighted gene co-expression network analysis identified modules of co-expressed genes, and hub genes important for cultivar responses to the two R. collo-cygni isolates. Metabolite analyses of the same leaves identified defense compounds such as p-CHDA and serotonin, correlating with responses observed at transcriptome and morphological level. Together these all-round responses of barley to R. collo-cygni provide molecular tools for further development of genetic and physiological markers that may be tested for improving tolerance of barley to this fungal pathogen.

Integrative transcript to proteome analysis of barley during Ramularia collo-cygni leaf spot development identified several proteins that are related to fungal recognition and infection responses

“…The transcriptome dataset has been previously published by us ( Sjokvist et al., 2019 ; Lemcke et al., 2021 ) and was used here for integrative analysis. To link the proteome and transcriptome data, each protein was mapped to the corresponding barley transcript identifier (Ensembl Plants) according to putative paralogue grouping by matching the identifiers from the input source ( Stare et al., 2017 ).…”

“…These studies have shown the involvement of ethylene and jasmonic acid signaling, along with the activation of the phenylpropanoid and flavonoid pathways in response to RLS, indicating typical defense processes against necrotrophic pathogens ( Sjokvist et al., 2019 ). The early production of p -coumaroyl-hydroxydehydroagmatin ( p -CHDA) and serotonin, which are both integral components in the process of cell wall fortification, has been identified at the metabolite level ( Lemcke et al., 2021 ). Furthermore, distinct expression levels of kinases, calmodulins, and defense proteins have been described as key differences between the defense responses in sensitive and resistant CVs ( Lemcke et al., 2021 ).…”

“…The early production of p -coumaroyl-hydroxydehydroagmatin ( p -CHDA) and serotonin, which are both integral components in the process of cell wall fortification, has been identified at the metabolite level ( Lemcke et al., 2021 ). Furthermore, distinct expression levels of kinases, calmodulins, and defense proteins have been described as key differences between the defense responses in sensitive and resistant CVs ( Lemcke et al., 2021 ). Although, to date, no complete resistance has been observed in the field for RLS, the symptoms vary significantly from one CV to another ( Pinnschmidt et al., 2006 ; McGrann et al., 2015 ), allowing the classification of these CVs into sensitive, intermediate, and tolerant categories.…”

“…The CVs had different sensitivities to Rcc , while the two isolates showed different degrees of aggressiveness. We took advantage of having these four combinations already analyzed in depth at the transcriptome level ( Lemcke et al., 2021 ) and performed a direct comparison of the observed molecular events at the transcript and protein levels.…”

Integration of targeted metabolome and transcript profiling of Pseudomonas syringae-triggered changes in defence-related phytochemicals in oat plants

“…Recently, novel insights of how plants respond to biological stresses have been uncovered by using a combination of transcriptomics and metabolomics analyses that pinpointed pivotal genes, proteins and metabolites involved in specific plant–pathogen interactions (Kim et al 2021b ; Lemcke et al 2021 ; Li et al 2022 ). Although a growing amount of research utilising a multi-omics approach for studying plant–pathogen interactions has been applied, such studies on oat plant defences, especially inoculated with P. syringae , are scarce.…”