WRR4B contributes to a broad-spectrum disease resistance against powdery mildew in Arabidopsis.

Oidium heveae HN1106, a powdery mildew (PM) that infects rubber trees, has been found to trigger disease resistance in Arabidopsis thaliana through ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1)-, PHYTOALEXIN DEFICIENT 4 (PAD4)- and salicylic acid (SA)-mediated signalling pathways. In this study, a typical TOLL-INTERLEUKIN 1 RECEPTOR, NUCLEOTIDE-BINDING, LEUCINE-RICH REPEAT (TIR-NB-LRR)-encoding gene, WHITE RUST RESISTANCE 4 (WRR4B), was identified to be required for the resistance against O. heveae in Arabidopsis. The expression of WRR4B was upregulated by O. heveae inoculation, and WRR4B positively regulated the expression of genes involved in SA biosynthesis, such as EDS1, PAD4, ICS1 (ISOCHORISMATE SYNTHASE 1), SARD1 (SYSTEMIC-ACQUIRED RESISTANCE DEFICIENT 1) and CBP60g (CALMODULIN-BINDING PROTEIN 60 G). Furthermore, WRR4B triggered self-amplification, suggesting that WRR4B mediated plant resistance through taking part in the SA-based positive feedback loop. In addition, WRR4B induced an EDS1-dependent hypersensitive response in Nicotiana benthamiana and contributed to disease resistance against three other PM species: Podosphaera xanthii, Erysiphe quercicola and Erysiphe neolycopersici, indicating that WRR4B is a broad-spectrum disease resistance gene against PMs.

Comparative proteomic analysis reveals molecular differences between incompatible and compatible interaction of Erysiphe pisi in garden pea.

Comparative proteome analysis of Erysiphe pisi-infected pea genotypes; JI-2480 carrying er2 resistant gene and Arkel, the susceptible genotype by liquid chromatography- mass spectrometry (LCMS/MS QTOF) at 72 h post inoculation (hpi) revealed several differentially abundant proteins (DAPs) of both the host and the pathogen. The functional annotation of proteins through gene enrichment and KEGG pathway analyses revealed strong up-regulation of pathogenesis related protein NPR1, proteins related to defense, transportation and signal transduction, hypersensitive response, cell wall modifications, phenylpropanoid and metabolic pathways in J-72. Significant abundance of membrane-related polypeptides, kinase domains and small GTPase signal transduction-related proteins suggested their major role in plant defense. The abundance of cellular antioxidant protein, catalase and its isozyme along with calreticulin-1 and 2 in J-72 confirmed their intervention in maintaining a redox balance in powdery mildew defense. High abundance levels of Glycolysis-related proteins indicated it as a major pathway for energy source during fungal growth. The majority of pathogenicity and virulence genes were downregulated in J-72 compared to A-72, while four EKA (Effectors homologues to Avk1 and Avra10) like avirulence proteins were significantly upregulated in incompatible interaction suggesting their role in eliciting hypersensitive response in pea against E. pisi.

Dual RNA-Seq analysis of Medicago truncatula and the pea powdery mildew Erysiphe pisi uncovers distinct host transcriptional signatures during incompatible and compatible interactions and pathogen effector candidates.

Powdery mildew (PM) is a serious fungal disease of legumes. To gain novel insights into PM pathogenesis and host resistance/susceptibility, we used dual RNA-Seq to simultaneously capture host and pathogen transcriptomes at 1 d post-inoculation of resistant and susceptible Medicago truncatula genotypes with the PM Erysiphe pisi (Ep). Differential expression analysis indicates that R-gene mediated resistance against Ep involves extensive transcriptional reprogramming. Functional enrichment of differentially expressed host genes and in silico analysis of co-regulated promoters suggests that amplification of PTI, activation of the JA/ET signaling network, and regulation of growth-defense balance correlate with resistance. In contrast, processes that favor biotrophy, including suppression of defense signaling and programmed cell death, and weaker cell wall defenses are important susceptibility factors. Lastly, Ep effector candidates and genes with known/putative virulence functions were identified, representing a valuable resource that can be leveraged to improve our understanding of legume-PM interactions.