Broad-scale phenotyping in Arabidopsis reveals varied involvement of RNA interference across diverse plant-microbe interactions.

RNA interference (RNAi) is a crucial mechanism in immunity against infectious microbes through the action of DICER-LIKE (DCL) and ARGONAUTE (AGO) proteins. In the case of the taxonomically diverse fungal pathogen and the oomycete , plant DCL and AGO proteins have proven roles as negative regulators of immunity, suggesting functional specialization of these proteins. To address this aspect in a broader taxonomic context, we characterized the colonization pattern of an informative set of and loss-of-function mutants in upon infection with a panel of pathogenic microbes with different lifestyles, and a fungal mutualist.

A fungal RNA-dependent RNA polymerase is a novel player in plant infection and cross-kingdom RNA interference.

Small RNAs act as fungal pathogen effectors that silence host target genes to promote infection, a virulence mechanism termed cross-kingdom RNA interference (RNAi). The essential pathogen factors of cross-kingdom small RNA production are largely unknown. We here characterized the RNA-dependent RNA polymerase (RDR)1 in the fungal plant pathogen Botrytis cinerea that is required for pathogenicity and cross-kingdom RNAi.

Extracellular RNAs released by plant-associated fungi: from fundamental mechanisms to biotechnological applications.

Extracellular RNAs are an emerging research topic in fungal-plant interactions. Fungal plant pathogens and symbionts release small RNAs that enter host cells to manipulate plant physiology and immunity. This communication via extracellular RNAs between fungi and plants is bidirectional.

Spotlight on plant RNA-containing extracellular vesicles.

Extracellular vesicles (EVs) carrying RNA have attracted growing attention in plant cell biology. For a long time, EV release or uptake through the rigid plant cell wall was considered to be impossible and RNA outside cells to be unstable. Identified EV biomarkers have brought new insights into functional roles of EVs to transport their RNA cargo for systemic spread in plants and into plant-invading pathogens.

Retrotransposons as pathogenicity factors of the plant pathogenic fungus Botrytis cinerea.

Background: Retrotransposons are genetic elements inducing mutations in all domains of life. Despite their detrimental effect, retrotransposons can become temporarily active during epigenetic reprogramming and cellular stress response, which may accelerate host genome evolution. In fungal pathogens, a positive role has been attributed to retrotransposons when shaping genome architecture and expression of genes encoding pathogenicity factors; thus, retrotransposons are known to influence pathogenicity.

Plant ARGONAUTE Protein Immunopurification for Pathogen Cross Kingdom Small RNA Analysis.

Over the last decade, it has been noticed that microbial pathogens and pests deliver small RNA (sRNA) effectors into their host plants to manipulate plant physiology and immunity for infection, known as cross kingdom RNA interference. In this process, fungal and oomycete parasite sRNAs hijack the plant ARGONAUTE (AGO)/RNA-induced silencing complex to post-transcriptionally silence host target genes. We hereby describe the methodological details of how we recovered cross kingdom sRNA effectors of the oomycete pathogen during infection of its host plant .

An Arabidopsis downy mildew non-RxLR effector suppresses induced plant cell death to promote biotroph infection.

Our understanding of obligate biotrophic pathogens is limited by lack of knowledge concerning the molecular function of virulence factors. We established Arabidopsis host-induced gene silencing (HIGS) to explore gene functions of Hyaloperonospora arabidopsidis, including CYSTEINE-RICH PROTEIN (HaCR)1, a potential secreted effector gene of this obligate biotrophic pathogen. HaCR1 HIGS resulted in H.

Oomycete small RNAs bind to the plant RNA-induced silencing complex for virulence.

The exchange of small RNAs (sRNAs) between hosts and pathogens can lead to gene silencing in the recipient organism, a mechanism termed cross-kingdom RNAi (ck-RNAi). While fungal sRNAs promoting virulence are established, the significance of ck-RNAi in distinct plant pathogens is not clear. Here, we describe that sRNAs of the pathogen , which represents the kingdom of oomycetes and is phylogenetically distant from fungi, employ the host plant's Argonaute (AGO)/RNA-induced silencing complex for virulence.

JASSY, a chloroplast outer membrane protein required for jasmonate biosynthesis.

Jasmonates are vital plant hormones that not only act in the stress response to biotic and abiotic influences, such as wounding, pathogen attack, and cold acclimation, but also drive developmental processes in cooperation with other plant hormones. The biogenesis of jasmonates starts in the chloroplast, where several enzymatic steps produce the jasmonate precursor 12-oxophytodienoic acid (OPDA) from α-linolenic acid. OPDA in turn is exported into the cytosol for further conversion into active jasmonates, which subsequently induces the expression of multiple genes in the nucleus.

Using Ustilago maydis as a Trojan Horse for In Situ Delivery of Maize Proteins.

Inspired by Homer´s Trojan horse myth, we engineered the maize pathogen Ustilago maydis to deliver secreted proteins into the maize apoplast permitting in vivo phenotypic analysis. This method does not rely on maize transformation but exploits microbial genetics and secretory capabilities of pathogens. Herein, it allows inspection of in vivo delivered secreted proteins with high spatiotemporal resolution at different kinds of infection sites and tissues.

Botrytis small RNA Bc-siR37 suppresses plant defense genes by cross-kingdom RNAi.

Pathogens secrete effector proteins to suppress host immune responses. Recently, we showed that an aggressive plant fungal pathogen Botrytis cinerea can also deliver small RNA effectors into host cells to suppress host immunity. B.

Bidirectional cross-kingdom RNAi and fungal uptake of external RNAs confer plant protection.

Aggressive fungal pathogens such as Botrytis and Verticillium spp. cause severe crop losses worldwide. We recently discovered that Botrytis cinerea delivers small RNAs (Bc-sRNAs) into plant cells to silence host immunity genes.

Small RNAs--the secret agents in the plant-pathogen interactions.

Eukaryotic regulatory small RNAs (sRNAs) that induce RNA interference (RNAi) are involved in a plethora of biological processes, including host immunity and pathogen virulence. In plants, diverse classes of sRNAs contribute to the regulation of host innate immunity. These immune-regulatory sRNAs operate through distinct RNAi pathways that trigger transcriptional or post-transcriptional gene silencing.

Conversations between kingdoms: small RNAs.

Humans, animals, and plants are constantly under attack from pathogens and pests, resulting in severe consequences on global human health and crop production. Small RNA (sRNA)-mediated RNA interference (RNAi) is a conserved regulatory mechanism that is involved in almost all eukaryotic cellular processes, including host immunity and pathogen virulence. Recent evidence supports the significant contribution of sRNAs and RNAi to the communication between hosts and some eukaryotic pathogens, pests, parasites, or symbiotic microorganisms.

Small RNAs: a new paradigm in plant-microbe interactions.

A never-ending arms race drives coevolution between pathogens and hosts. In plants, pathogen attacks invoke multiple layers of host immune responses. Many pathogens deliver effector proteins into host cells to suppress host immunity, and many plants have evolved resistance proteins to recognize effectors and trigger robust resistance.

Fungal small RNAs suppress plant immunity by hijacking host RNA interference pathways.

Botrytis cinerea, the causative agent of gray mold disease, is an aggressive fungal pathogen that infects more than 200 plant species. Here, we show that some B. cinerea small RNAs (Bc-sRNAs) can silence Arabidopsis and tomato genes involved in immunity.

Components of variance in transcriptomics based on electrophoretic separation of cDNA fragments (cDNA-AFLP).

The sources of variance and errors in transcriptomics based on the electrophoretic separation of amplified cDNA fragments were investigated using cDNA-amplified fragment length polymorphism (AFLP). Transcriptome profiles of the plant-pathogenic fungus Verticillium longisporum were generated by a standard cDNA-AFLP protocol followed by electrophoretic separation of amplified DNA fragments in flatbed polyacrylamide gels with fluorescence detection as well as by capillary electrophoresis (DNA sequencer). The total variance was partitioned into contributions of cDNA synthesis, adapter ligation, preamplification, amplification, and electrophoresis.

Improved coverage of cDNA-AFLP by sequential digestion of immobilized cDNA.

Background: cDNA-AFLP is a transcriptomics technique which does not require prior sequence information and can therefore be used as a gene discovery tool. The method is based on selective amplification of cDNA fragments generated by restriction endonucleases, electrophoretic separation of the products and comparison of the band patterns between treated samples and controls. Unequal distribution of restriction sites used to generate cDNA fragments negatively affects the performance of cDNA-AFLP.