Transcriptome Analysis of Rlm2-Mediated Host Immunity in the Brassica napus–Leptosphaeria maculans Pathosystem

Abstract

Our study investigated disease resistance in the Brassica napus–Leptosphaeria maculans pathosystem using a combination of laser microdissection, dual RNA sequencing, and physiological validations of large-scale gene sets. The use of laser microdissection improved pathogen detection and identified putative L. maculans effectors and lytic enzymes operative during host colonization. Within 24 h of inoculation, we detected large shifts in gene activity in resistant cotyledons associated with jasmonic acid and calcium signaling pathways that accelerated the plant defense response. Sequencing data were validated through the direct quantification of endogenous jasmonic acid levels. Additionally, resistance against L. maculans was abolished when the calcium chelator EGTA was applied to the inoculation site, providing physiological evidence of the role of calcium in B. napus immunity against L. maculans. We integrated gene expression data with all available information on cis-regulatory elements and transcription factor binding affinities to better understand the gene regulatory networks underpinning plant resistance to hemibiotrophic pathogens. These in silico analyses point to early cellular reprogramming during host immunity that are coordinated by CAMTA, BZIP, and bHLH transcription factors. Together, we provide compelling genetic and physiological evidence into the programming of plant resistance against fungal pathogens.

The Brassica napus wall‐associated kinase‐like (WAKL) gene Rlm9 provides race‐specific blackleg resistance

“…Transcription time course profiles were generated by RNA‐Seq (Illumina, San Diego, CA, USA) for the B. napus cultivars Topas DH16516 (no R gene) and Darmor ( Rlm9 ) during infection with the L. maculans isolate 00–100 (avirulence profile A2‐3‐5‐6‐(8)‐9‐(10)‐L1‐L2‐L4 (Larkan et al ., 2016)) with sampling at 0, 3, 6 and 9 days after inoculation. Additional data for the lines Topas‐ Rlm2 and Topas‐ Rlm3 , growth conditions, tissue sampling, RNA processing and read mapping protocols were as previously described (Becker et al ., 2019; Haddadi et al ., 2019). Confirmation of the predicted coding region and protein sequence was obtained by aligning merged RNA sequencing reads to the Darmor genome sequence using Bowtie2 (http://bowtie-bio.sourceforge.net/bowtie2/manual.shtml) and CLC Genomics Workbench 11 (https://www.qiagenbioinformatics.com/products/clc-genomics-workbench/).…”

Identification and characterization of genes frequently responsive to Xanthomonas oryzae pv. oryzae and Magnaporthe oryzae infections in rice

“…Transcriptomic analysis is a powerful tool to reveal the interactions between host and pathogen [61][62][63][64]. In this study, we analyzed 35 pairs of samples from 69 pairs of Xooor Mor-infected rice microarray samples deposited in the GEO database.…”

Recent Findings Unravel Genes and Genetic Factors Underlying Leptosphaeria maculans Resistance in Brassica napus and Its Relatives

“…Similarly, AvrLm1 suppresses SA and JA signalling pathways in transient gene expression of A. thaliana (Columbia-0 line) and targets phosphorylation of B. napus mitogen-activated protein kinase (MAP_k) 9 (BnMAP_k9) gene, which leads to an increase in cell death in A. thaliana [210]. As AvrLm2 suppressed JA signalling, an MAP_k signal was induced; the mechanism could be similar to AvrLm1 to BnMAP_k9 gene but needs to further verification [211]. In a different study in A. thaliana-pathogen interaction, as the AP2C1 gene (protein phosphatase gene) influenced MAP_k4 and MAP_k6 genes, the levels of JA and ET signalling genes were lowered, which subsequently compromised the plant immunity [212].…”

“…Generally, when L. maculans enters the plant, SA and JA-related genes are affected and act as initial defence compounds [84,209,[216][217][218][223][224][225]. There are also genes that may contribute or act as basal defence, such as pattern recognition receptor CERK1 (e.g., chitin elicitor receptor kinase 1), WRKY transcription factors (TF) (e.g., WRKYs 33, 40 and 51), glucosinolate-related genes (e.g., cytochrome P450, SUPERROOT1, and nitrile-specifier protein 5), and calcium-related biological functions (e.g., homologs of CAM1, CAM5 and CAM7; CYCLIC NUCLEOTIDE-GATED CALCIUM CHANNEL 3, 12 and 19; CALMODULIN-DOMAIN PROTEIN KINASE 5, 9; CALCIUM-DEPENDENT PROTEIN KINASE 6 and 28; and CALCINEURIN B-LIKE GENE 1) [211,216].…”