RNA-Seq and secondary metabolite analyses reveal a putative defence-transcriptome in Norway spruce (Picea abies) against needle bladder rust (Chrysomyxa rhododendri) infection

Abstract

Background Norway spruce trees in subalpine forests frequently face infections by the needle rust fungus Chrysomyxa rhododendri, which causes significant growth decline and increased mortality of young trees. Yet, it is unknown whether trees actively respond to fungal attack by activating molecular defence responses and/or respective gene expression. Results Here, we report results from an infection experiment, in which the transcriptomes (via RNA-Seq analysis) and phenolic profiles (via UHPLC-MS) of control and infected trees were compared over a period of 39 days. Gene expression between infected and uninfected ramets significantly differed after 21 days of infection and revealed already known, but also novel candidate genes involved in spruce molecular defence against pathogens. Conclusions Combined RNA-Seq and biochemical data suggest that Norway spruce response to infection by C. rhododendri is restricted locally and primarily activated between 9 and 21 days after infestation, involving a potential isolation of the fungus by a hypersensitive response (HR) associated with an activation of phenolic pathways. Identified key regulatory genes represent a solid basis for further specific analyses in spruce varieties with varying susceptibility, to better characterise resistant clones and to elucidate the resistance mechanism.

Differential alteration of plant functions by homologous fungal candidate effectors

“…In rust fungi, different approaches are used in the functional characterization of these proteins, including analysis of subcellular localization in planta[19,25,28,30,31], infection assays in true host or in a model plant, and induction/repression of plant cell death[19,30,36,37]. The transcriptome or metabolome of the host in responses to the pathogen are frequently evaluated[38][39][40][41][42][43], but the assessment of the role of individual CEs in these processes is not easily measured and seldom analyzed[22,44].Here we investigated 14 CEs from Melampsora larici-populina by evaluating their individual impact on the transcriptome and metabolome of stable transgenic Arabidopsis plants. By studying the impact of several individual CEs, we were able to compare patterns of gene and metabolite deregulation.…”

Unrelated Fungal Rust Candidate Effectors Act on Overlapping Plant Functions

“…In rust fungi, different approaches are used in the functional characterization of these proteins, including analysis of subcellular localization in planta [ 22 , 27 , 28 , 30 , 50 ], infection assays in true host or in a model plant, and induction/repression of plant cell death [ 22 , 30 , 57 , 58 ]. The transcriptome or metabolome of the host in responses to the pathogen are frequently evaluated [ 59 , 60 , 61 , 62 , 63 , 64 ], but the assessment of the role of individual CEs in these processes is not easily measured and seldom analyzed [ 24 , 65 ]. Here, we investigated 14 CEs from Melampsora larici-populina by evaluating their individual impact on the transcriptome and metabolome of stable transgenic Arabidopsis plants.…”

Transcriptomic analysis of Dubas bug (Ommatissus lybicus Bergevin) infestation to Date Palm

“…GO annotation showed that 4,341 DEGs belonging to cellular, bio-chemical and molecular components. Recent study of Norway spruce tree's transcriptome showed involvement of molecular function, biological process but no cellular component term during needle bladder rust, suggesting a variable responses of DB infection 46 . During DB infection, it was noted that 73 DEGs were related to plant-pathogen interaction, suggesting a post-herbivory genetic cascade.…”

“…Previously, CaM/CML protein family regulate cellular responses to pathogenic induced HR responses in grapevine 54 . Activation of HR responses in DB infection could have played role in reducing infection caused by extricating cell death in neighboring cells 46 . A similar conclusion was also revealed by Trujillo-Moya et al 46 Norway spruce.…”

“…Activation of HR responses in DB infection could have played role in reducing infection caused by extricating cell death in neighboring cells 46 . A similar conclusion was also revealed by Trujillo-Moya et al 46 Norway spruce. 55 , a considerable activation of MAPK and WRKY related genes are used to induce defense responses 36,56 .…”