Proteomic analysis on zoxamide-induced sensitivity changes in Phytophthora cactorum

Deciphering fungicide resistance in Phytophthora: mechanisms, prevalence, and sustainable management approaches

The genus Phytophthora contains more than 100 plant pathogenic species that parasitize a wide range of plants, including economically important fruits, vegetables, cereals, and forest trees, causing significant losses. Global agriculture is seriously threatened by fungicide resistance in Phytophthora species, which makes it imperative to fully comprehend the mechanisms, frequency, and non-chemical management techniques related to resistance mutations. The mechanisms behind fungicide resistance, such as target-site mutations, efflux pump overexpression, overexpression of target genes and metabolic detoxification routes for fungicides routinely used against Phytophthora species, are thoroughly examined in this review. Additionally, it assesses the frequency of resistance mutations in various Phytophthora species and geographical areas, emphasizing the rise of strains that are resistant to multiple drugs. The effectiveness of non-chemical management techniques, including biological control, host resistance, integrated pest management plans, and cultural practices, in reducing fungicide resistance is also thoroughly evaluated. The study provides important insights for future research and the development of sustainable disease management strategies to counter fungicide resistance in Phytophthora species by synthesizing current information and identifying knowledge gaps.

The devastating oomycete phytopathogen Phytophthora cactorum: Insights into its biology and molecular features

Phytophthora cactorum is one of the most economically important soilborne oomycete pathogens in the world. It infects more than 200 plant species spanning 54 families, most of which are herbaceous and woody species. Although traditionally considered to be a generalist, marked differences of P. cactorum isolates occur in degree of pathogenicity to different hosts. As the impact of crop loss caused by this species has increased recently, there has been a tremendous increase in the development of new tools, resources, and management strategies to study and combat this devastating pathogen. This review aims to integrate recent molecular biology analyses of P. cactorum with the current knowledge of the cellular and genetic basis of its growth, development, and host infection. The goal is to provide a framework for further studies of P. cactorum by highlighting important biological and molecular features, shedding light on the functions of pathogenicity factors, and developing effective control measures.

TAXONOMY

P. cactorum (Leb. & Cohn) Schröeter: kingdom Chromista; phylum Oomycota; class Oomycetes; order Peronosporales; family Peronosporaceae; genus Phytophthora.

HOST RANGE

Infects about 200 plant species in 154 genera representing 54 families. Economically important host plants include strawberry, apple, pear, Panax spp., and walnut.

DISEASE SYMPTOMS

The soilborne pathogen often causes root, stem, collar, crown, and fruit rots, as well as foliar infection, stem canker, and seedling damping off.

Cinnamaldehyde inhibits the growth of Phytophthora capsici through disturbing metabolic homoeostasis

Background

Phytophthora capsici Leonian (P. capsici) can cause wilting and roots rotting on pepper and other cash crops. The new fungicide cinnamaldehyde (CA) has high activity against this pathogen. However, its potential mechanism is still unknown.

Methods

In order to gain insights into the mechanism, isobaric tags for relative and absolute quantification (iTRAQ)-based quantitative proteomics was used to analyze P. capsici treated with CA. The iTRAQ results were evaluated by parallel reaction monitoring (PRM) analysis and quantitative real-time PCR (qRT-PCR) analysis. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis was used to speculate the biochemical pathways that the agent may act on.

Results

The results showed that 1502 differentially expressed proteins were identified, annotated and classified into 209 different terms (like metabolic process, cellular process, single-organism process) based on Gene Ontology (GO) functional enrichment analysis and nine different pathways (glyoxylate and dicarboxylate metabolism, fatty acid metabolism and so on) based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. This study suggested that CA disordered fatty acid metabolism, polysaccharide metabolism and leucine metabolism. Based on PRM analysis, five proteins including CAMK/CAMK1 protein kinase, glucan 1,3-beta-glucosidase, 1,3-beta-glucanosyltransferase, methylcrotonoyl-CoA carboxylase subunit alpha and isovaleryl-CoA dehydrogenase were down-regulated in P. capsici treated with CA. Furthermore, the qRT-PCR analysis showed that the gene expression level of the interested proteins was consistent with the protein expression level, except for CAMK/CAMK1 protein kinase, acetyl-CoA carboxylase and fatty acid synthase subunit alpha.

Conclusions

CA destroyed the metabolic homoeostasisof P. capsici, which led to cell death. This is the first proteomic analysis of P. capsici treated with CA, which may provide an important information for exploring the mechanism of the fungicide CA against P. capsici.

Benzothiazole inhibits the growth of Phytophthora capsici through inducing apoptosis and suppressing stress responses and metabolic detoxification

Benzothiazole (BZO) is an antimicrobial secondary metabolite volatilized by many plants and microbes. However, the mechanism of BZO against phytopathogens is still unclear. Here, we found that BZO has antimicrobial activity against the oomycete pathogen Phytophthora capsici. Transcriptome and proteome analyses demonstrated that BZO significantly suppressed the expression of genes and proteins involved in morphology, abiotic stress defense and detoxification, but induced the activity of apoptosis. Annexin V-FITC/PI staining confirmed that the process of apoptosis was significantly induced by BZO at concentration of 150 mg L^-1. FITC-phalloidin actin-cytoskeleton staining combined with hyphal cell wall staining and hyphal ultrastructure studies further confirmed that BZO disrupted the cell membrane and hyphal morphology through disrupting the cytoskeleton, eventually inhibiting the growth of hyphae. These data demonstrated that BZO has multiple modes of action and may act as potential leading compound for the development of new oomycete fungicides. These results also showed that the combination of transcriptomic and proteomic approaches was a useful method for exploring the novel antifungal mechanisms of natural compounds.

The Phytophthora cactorum genome provides insights into the adaptation to host defense compounds and fungicides

Phytophthora cactorum is a homothallic oomycete pathogen, which has a wide host range and high capability to adapt to host defense compounds and fungicides. Here we report the 121.5 Mb genome assembly of the P. cactorum using the third-generation single-molecule real-time (SMRT) sequencing technology. It is the second largest genome sequenced so far in the Phytophthora genera, which contains 27,981 protein-coding genes. Comparison with other Phytophthora genomes showed that P. cactorum had a closer relationship with P. parasitica, P. infestans and P. capsici. P. cactorum has similar gene families in the secondary metabolism and pathogenicity-related effector proteins compared with other oomycete species, but specific gene families associated with detoxification enzymes and carbohydrate-active enzymes (CAZymes) underwent expansion in P. cactorum. P. cactorum had a higher utilization and detoxification ability against ginsenosides-a group of defense compounds from Panax notoginseng-compared with the narrow host pathogen P. sojae. The elevated expression levels of detoxification enzymes and hydrolase activity-associated genes after exposure to ginsenosides further supported that the high detoxification and utilization ability of P. cactorum play a crucial role in the rapid adaptability of the pathogen to host plant defense compounds and fungicides.

Trends and Challenges in Pesticide Resistance Detection

Pesticide resistance is a crucial factor to be considered when developing strategies for the minimal use of pesticides while maintaining pesticide efficacy. This goal requires monitoring the emergence and development of resistance to pesticides in crop pests. To this end, various methods for resistance diagnosis have been developed for different groups of pests. This review provides an overview of biological, biochemical, and molecular methods that are currently used to detect and quantify pesticide resistance. The agronomic, technical, and economic advantages and drawbacks of each method are considered. Emerging technologies are also described, with their associated challenges and their potential for the detection of resistance mechanisms likely to be selected by current and future plant protection methods.