Terpenoid and lipid profiles vary in different Phytophthora cactorum - strawberry interactions

Comparative Transcriptomics of Soybean Genotypes with Partial Resistance Toward Phytophthora sojae, Conrad, and M92-220 to Moderately Susceptible Fast Neutron Mutant Soybeans and Sloan

The breeding of disease-resistant soybeans cultivars to manage Phytophthora root and stem rot caused by the pathogen Phytophthora sojae involves combining quantitative disease resistance (QDR) and Rps gene-mediated resistance. To identify and confirm potential mechanisms of QDR toward P. sojae, we conducted a time course study comparing changes in gene expression among Conrad and M92-220 with high QDR to susceptible genotypes, Sloan, and three mutants derived from fast neutron irradiation of M92-220. Differentially expressed genes from Conrad and M92-220 indicated several shared defense-related pathways at the transcriptomic level but also defense pathways unique to each cultivar, such as stilbenoid, diarylheptanoid, and gingerol biosynthesis and monobactam biosynthesis. Gene Ontology pathway analysis showed that the susceptible fast neutron mutants lacked enrichment of three terpenoid-related pathways and two cell wall-related pathways at either one or both time points, in contrast to M92-220. The susceptible mutants also lacked enrichment of potentially important Kyoto Encyclopedia of Genes and Genomes pathways at either one or both time points, including sesquiterpenoid and triterpenoid biosynthesis; thiamine metabolism; arachidonic acid; stilbenoid, diarylheptanoid, and gingerol biosynthesis; and monobactam biosynthesis. Additionally, 31 genes that were differentially expressed in M92-220 following P. sojae infection were not expressed in the mutants. These 31 genes have annotations related to unknown proteins; valine, leucine, and isoleucine biosynthesis; and protein and lipid metabolic processes. The results of this study confirm previously proposed mechanisms of QDR, provide evidence for potential novel QDR pathways in M92-220, and further our understanding of the complex network associated with QDR mechanisms in soybean toward P. sojae.

Non-invasive assessment and visualization of Phytophthora cactorum infection in strawberry crowns using quantitative magnetic resonance imaging

Phytophthora cactorum is an oomycete species that causes enormous losses on horticultural crops, including strawberries. The purpose of this work was to investigate the alterations caused by P. cactorum inoculation in hydroponically grown strawberry plantlets (Fragaria × ananassa Duch.) using quantitative magnetic resonance imaging (qMRI). It was observed that with MRI, spatial and temporal progression of the infection could be observed in the crown using quantitative MR parameters, namely relaxation time maps. Relaxation times are numeric subject-specific properties that describe the MR signal behavior in an examined anatomical region. Elevated [Formula: see text] relaxation time values were observed inside the infected plant crowns with respect to the healthy references. The [Formula: see text] and [Formula: see text] values of healthy plants were small in the crown region and further diminished during the development of the plant. Furthermore, elevated [Formula: see text] relaxation time values were seen in regions where P. cactorum progression was observed in corresponding plant dissection photographs. Quantitative susceptibility maps (QSM) were calculated to estimate the local magnetic field inhomogeneities. The QSM suggests magnetic susceptibility differences near the center of the pith. This study provides novel non-invasive information on the structure and development of strawberry plants and the effects caused by the P. cactorum infection.

Comparative metabolomic study of fungal foliar endophytes and their long-lived host Astrocaryum sciophilum: a model for exploring the chemodiversity of host-microbe interactions

Introduction

In contrast to the dynamics observed in plant/pathogen interactions, endophytic fungi have the capacity to establish enduring associations within their hosts, leading to the development of a mutually beneficial relationship that relies on specialized chemical interactions. Research indicates that the presence of endophytic fungi has the ability to significantly modify the chemical makeup of the host organism. Our hypothesis proposes the existence of a reciprocal exchange of chemical signals between plants and fungi, facilitated by specialized chemical processes that could potentially manifest within the tissues of the host. This research aimed to precisely quantify the portion of the cumulative fungal endophytic community's metabolome detectable within host leaves, and tentatively evaluate its relevance to the host-endophyte interplay. The understory palm Astrocaryum sciophilum (Miq.) Pulle was used as a interesting host plant because of its notable resilience and prolonged life cycle, in a tropical ecosystem.

Method

Using advanced metabolome characterization, including UHPLC-HRMS/MS and molecular networking, the study explored enriched metabolomes of both host leaves and 15 endophytic fungi. The intention was to capture a metabolomic "snapshot" of both host and endophytic community, to achieve a thorough and detailed analysis.

Results and discussion

This approach yielded an extended MS-based molecular network, integrating diverse metadata for identifying host- and endophyte-derived metabolites. The exploration of such data (>24000 features in positive ionization mode) enabled effective metabolome comparison, yielding insights into cultivable endophyte chemodiversity and occurrence of common metabolites between the holobiont and its fungal communities. Surprisingly, a minor subset of features overlapped between host leaf and fungal samples despite significant plant metabolome enrichment. This indicated that fungal metabolic signatures produced in vitro remain sparingly detectable in the leaf. Several classes of primary metabolites were possibly shared. Specific fungal metabolites and/or compounds of their chemical classes were only occasionally discernible in the leaf, highlighting endophytes partial contribution to the overall holobiont metabolome. To our knowledge, the metabolomic study of a plant host and its microbiome has rarely been performed in such a comprehensive manner. The general analytical strategy proposed in this paper seems well-adapted for any study in the field of microbial- or microbiome-related MS and can be applied to most host-microbe interactions.

Secondary Metabolites and Their Role in Strawberry Defense

Strawberry is a high-value commercial crop and a model for the economically important Rosaceae family. Strawberry is vulnerable to attack by many pathogens that can affect different parts of the plant, including the shoot, root, flowers, and berries. To restrict pathogen growth, strawberry produce a repertoire of secondary metabolites that have an important role in defense against diseases. Terpenes, allergen-like pathogenesis-related proteins, and flavonoids are three of the most important metabolites involved in strawberry defense. Genes involved in the biosynthesis of secondary metabolites are induced upon pathogen attack in strawberry, suggesting their transcriptional activation leads to a higher accumulation of the final compounds. The production of secondary metabolites is also influenced by the beneficial microbes associated with the plant and its environmental factors. Given the importance of the secondary metabolite pathways in strawberry defense, we provide a comprehensive overview of their literature and their role in the defense responses of strawberry. We focus on terpenoids, allergens, and flavonoids, and discuss their involvement in the strawberry microbiome in the context of defense responses. We discuss how the biosynthetic genes of these metabolites could be potential targets for gene editing through CRISPR-Cas9 techniques for strawberry crop improvement.

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.