Phytophthora sojae effector PsAvh113 associates with the soybean transcription factor GmDPB to inhibit catalase-mediated immunity

TaCAMTA4 negatively regulates H2O2-dependent wheat leaf rust resistance by activating catalase 1 expression

Leaf rust, caused by Puccinia triticina Erikss. (Pt), is a serious disease threatening wheat (Triticum aestivum L.) production worldwide. Hydrogen peroxide (H2O2) triggered by Pt infection in resistant wheat cultivars cause oxidative damage directly to biomolecules or is activated by calcium signaling and mediates the hypersensitive response. Calmodulin-binding transcriptional activator 4 (TaCAMTA4) has been reported to negatively regulate wheat resistance to Pt. In this study, we found that TaCAMTA4 was induced by Pt race 165 in its compatible host harboring the Pt-resistant locus Lr26, TcLr26, and silencing of TaCAMTA4 increased local H2O2 accumulation and Pt resistance. Subcellular localization and autoactivation tests revealed that TaCAMTA4 is a nucleus-localized transcriptional activator. Furthermore, 4 DNA motifs recognized by TaCAMTA4 were identified by transcription factor-centered Y1H. Through analyzing the transcriptome database, 4 gene clusters were identified, each containing a different DNA motif on each promoter. Among them, the expression of catalase 1 (TaCAT1) with motif-1 was highly induced in the compatible interaction and was decreased when TaCAMTA4 was silenced. The results of electrophoretic mobility shift assay, ChIP-qPCR, and RT-qPCR further showed that TaCAMTA4 directly bound motif-1 in the TaCAT1 promoter. Furthermore, silencing of TaCAT1 resulted in enhanced resistance to Pt and increased local H2O2 accumulation in wheat, which is consistent with that of TaCAMTA4. Since calmodulin-binding transcription activators are Ca2+ sensors and catalases catalyze the decomposition of H2O2, we hypothesize that Ca2+ regulates the plant immune networks that are controlled by H2O2 and implicate a potential mechanism for Pt to suppress resistance by inducing the expression of the TaCAMTA4-TaCAT1 module, which consequently enhances H2O2 scavenging and attenuates H2O2-dependent resistance.

Use of CRISPR Technology in Gene Editing for Tolerance to Biotic Factors in Plants: A Systematic Review

The objective of this systematic review (SR) was to select studies on the use of gene editing by CRISPR technology related to plant resistance to biotic stresses. We sought to evaluate articles deposited in six electronic databases, using pre-defined inclusion and exclusion criteria. This SR demonstrates that countries such as China and the United States of America stand out in studies with CRISPR/Cas. Among the most studied crops are rice, tomatoes and the model plant Arabidopsis thaliana. The most cited biotic agents include the genera, Xanthomonas, Manaporthe, Pseudomonas and Phytophthora. This SR also identifies several CRISPR/Cas-edited genes and demonstrates that plant responses to stressors are mediated by many complex signaling pathways. The Cas9 enzyme is used in most articles and Cas12 and 13 are used as additional editing tools. Furthermore, the quality of the articles included in this SR was validated by a risk of bias analysis. The information collected in this SR helps to understand the state of the art of CRISPR/Cas aimed at improving resistance to diseases and pests to understand the mechanisms involved in most host-pathogen relationships. This SR shows that the CRISPR/Cas system provides a straightforward method for rapid gene targeting, providing useful information for plant breeding programs.

Suppression of plant immunity by Verticillium dahliae effector Vd6317 through AtNAC53 association

Verticillium dahliae, a soil-borne fungal pathogen, compromises host innate immunity by secreting a plethora of effectors, thereby facilitating host colonization and causing substantial yield and quality losses. The mechanisms underlying the modulation of cotton immunity by V. dahliae effectors are predominantly unexplored. In this study, we identified that the V. dahliae effector Vd6317 inhibits plant cell death triggered by Vd424Y and enhances PVX viral infection in Nicotiana benthamiana. Attenuation of Vd6317 significantly decreased the virulence of V. dahliae, whereas ectopic expression of Vd6317 in Arabidopsis and cotton enhanced susceptibility to V. dahliae infection, underscoring Vd6317's critical role in pathogenicity. We observed that Vd6317 targeted the Arabidopsis immune regulator AtNAC53, thereby impeding its transcriptional activity on the defense-associated gene AtUGT74E2. Arabidopsis nac53 and ugt74e2 mutants exhibited heightened sensitivity to V. dahliae compared to wild-type plants. A mutation at the conserved residue 193L of Vd6317 abrogated its interaction with AtNAC53 and reduced the virulence of V. dahliae, which was partially attributable to a reduction in Vd6317 protein stability. Our findings unveil a hitherto unrecognized regulatory mechanism by which the V. dahliae effector Vd6317 directly inhibits the plant transcription factor AtNAC53 activity to suppress the expression of AtUGT74E2 and plant defense.

The RXLR effector PpE18 of Phytophthora parasitica is a virulence factor and suppresses peroxisome membrane-associated ascorbate peroxidase NbAPX3-1-mediated plant immunity

Phytophthora parasitica causes diseases on a broad range of host plants. It secretes numerous effectors to suppress plant immunity. However, only a few virulence effectors in P. parasitica have been characterized. Here, we highlight that PpE18, a conserved RXLR effector in P. parasitica, was a virulence factor and suppresses Nicotiana benthamiana immunity. Utilizing luciferase complementation, co-immunoprecipitation, and GST pull-down assays, we determined that PpE18 targeted NbAPX3-1, a peroxisome membrane-associated ascorbate peroxidase with reactive oxygen species (ROS)-scavenging activity and positively regulates plant immunity in N. benthamiana. We show that the ROS-scavenging activity of NbAPX3-1 was critical for its immune function and was hindered by the binding of PpE18. The interaction between PpE18 and NbAPX3-1 resulted in an elevation of ROS levels in the peroxisome. Moreover, we discovered that the ankyrin repeat-containing protein NbANKr2 acted as a positive immune regulator, interacting with both NbAPX3-1 and PpE18. NbANKr2 was required for NbAPX3-1-mediated disease resistance. PpE18 competitively interfered with the interaction between NbAPX3-1 and NbANKr2, thereby weakening plant resistance. Our results reveal an effective counter-defense mechanism by which P. parasitica employed effector PpE18 to suppress host cellular defense, by suppressing biochemical activity and disturbing immune function of NbAPX3-1 during infection.

Phytophthora sojae Effector PsAvh113 Targets Transcription Factors in Nicotiana benthamiana

Phytophthora sojae is a type of pathogenic oomycete that causes Phytophthora root stem rot (PRSR), which can seriously affect the soybean yield and quality. To subvert immunity, P. sojae secretes a large quantity of effectors. However, the molecular mechanisms regulated by most P. sojae effectors, and their host targets remain unexplored. Previous studies have shown that the expression of PsAvh113, an effector secreted by Phytophthora sojae, enhances viral RNA accumulations and symptoms in Nicotiana benthamiana via VIVE assay. In this study, we analyzed RNA-sequencing data based on disease symptoms in N. benthamiana leaves that were either mocked or infiltrated with PVX carrying the empty vector (EV) and PsAvh113. We identified 1769 differentially expressed genes (DEGs) dependent on PsAvh113. Using stricter criteria screening and Gene Ontology (GO) and Kyoto Encyclopaedia of Genes and Genomes (KEGG) analysis of DEGs, we found that 38 genes were closely enriched in response to PsAvh113 expression. We selected three genes of N. benthamiana (NbNAC86, NbMyb4, and NbERF114) and found their transcriptional levels significantly upregulated in N. benthamiana infected with PVX carrying PsAvh113. Furthermore, individual silencing of these three genes promoted P. capsici infection, while their overexpression increased resistance to P. capsici in N. benthamiana. Our results show that PsAvh113 interacts with transcription factors NbMyb4 and NbERF114 in vivo. Collectively, these data may help us understand the pathogenic mechanism of effectors and manage PRSR in soybeans.

Maize catalases are recruited by a virus to modulate viral multiplication and infection

Given the detrimental effects of excessive reactive oxygen species (ROS) accumulation in plant cells, various antioxidant mechanisms have evolved to maintain cellular redox homeostasis, encompassing both enzymatic components (e.g., catalase, superoxide dismutase) and non-enzymatic ones. Despite extensive research on the role of antioxidant systems in plant physiology and responses to abiotic stresses, the potential exploitation of antioxidant enzymes by plant viruses to facilitate viral infection remains insufficiently addressed. Herein, we demonstrate that maize catalases (ZmCATs) exhibited up-regulated enzymatic activities upon sugarcane mosaic virus (SCMV) infection. ZmCATs played crucial roles in SCMV multiplication and infection by catalysing the decomposition of excess cellular H2 O2 and promoting the accumulation of viral replication-related cylindrical inclusion (CI) protein through interaction. Peroxisome-localized ZmCATs were found to be distributed around SCMV replication vesicles in Nicotiana benthamiana leaves. Additionally, the helper component-protease (HC-Pro) of SCMV interacted with ZmCATs and enhanced catalase activities to promote viral accumulation. This study unveils a significant involvement of maize catalases in modulating SCMV multiplication and infection through interaction with two viral factors, thereby enhancing our understanding regarding viral strategies for manipulating host antioxidant mechanisms towards robust viral accumulation.

RxLR Effectors: Master Modulators, Modifiers and Manipulators

Cytoplasmic effectors with an Arg-any amino acid-Arg-Leu (RxLR) motif are encoded by hundreds of genes within the genomes of oomycete Phytophthora spp. and downy mildew pathogens. There has been a dramatic increase in our understanding of the evolution, function, and recognition of these effectors. Host proteins with a wide range of subcellular localizations and functions are targeted by RxLR effectors. Many processes are manipulated, including transcription, post-translational modifications, such as phosphorylation and ubiquitination, secretion, and intracellular trafficking. This involves an array of RxLR effector modes-of-action, including stabilization or destabilization of protein targets, altering or disrupting protein complexes, inhibition or utility of target enzyme activities, and changing the location of protein targets. Interestingly, approximately 50% of identified host proteins targeted by RxLR effectors are negative regulators of immunity. Avirulence RxLR effectors may be directly or indirectly detected by nucleotide-binding leucine-rich repeat resistance (NLR) proteins. Direct recognition by a single NLR of RxLR effector orthologues conserved across multiple Phytophthora pathogens may provide wide protection of diverse crops. Failure of RxLR effectors to interact with or appropriately manipulate target proteins in nonhost plants has been shown to restrict host range. This knowledge can potentially be exploited to alter host targets to prevent effector interaction, providing a barrier to host infection. Finally, recent evidence suggests that RxLR effectors, like cytoplasmic effectors from fungal pathogen Magnaporthe oryzae, may enter host cells via clathrin-mediated endocytosis. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Genome-Wide Identification of Catalase Gene Family and the Function of SmCAT4 in Eggplant Response to Salt Stress

Salinity is an important abiotic stress, damaging plant tissues by causing a burst of reactive oxygen species (ROS). Catalase (CAT) enzyme coded by Catalase (CAT) genes are potent in reducing harmful ROS and hydrogen peroxide (H2O2) produced. Herein, we performed bioinformatics and functional characterization of four SmCAT genes, retrieved from the eggplant genome database. Evolutionary analysis CAT genes revealed that they are divided into subgroups I and II. The RT-qPCR analysis of SmCAT displayed a differential expression pattern in response to abiotic stresses. All the CAT proteins of eggplant were localized in the peroxisome, except for SmCAT4, which localized in the cytomembrane and nucleus. Silencing of SmCAT4 compromised the tolerance of eggplant to salt stress. Suppressed expression levels of salt stress defense related genes SmTAS14 and SmDHN1, as well as increase of H2O2 content and decrease of CAT enzyme activity was observed in the SmCAT4 silenced eggplants. Our data provided insightful knowledge of CAT gene family in eggplant. Positive regulation of eggplant response to salinity by SmCAT4 provides resource for future breeding programs.