Decoding resilience: ecology, regulation, and evolution of biosynthetic gene clusters.

Secondary metabolism is crucial for plant survival and can generate chemistry with nutritional, therapeutic, and industrial value. Biosynthetic genes of selected secondary metabolites cluster within localised chromosomal regions. The arrangement of these biosynthetic gene clusters (BGCs) challenges the long-held model of random gene order in eukaryotes, raising questions about their regulation, ecological significance, and evolution.

Role of PMR4 and PDLP1 in priming of early acting penetration defense by resistance-inducing β-amino acids.

R-β-homoserine (RBH) and β-aminobutyric acid (BABA) induce resistance against the oomycete () in Arabidopsis, which is based on priming of multiple defense layers, including early acting penetration resistance at the cell wall. Here, we have examined the molecular basis of RBH- and BABA-primed defense by cell wall papillae against . Three-dimensional reconstruction of -induced papillae by confocal microscopy revealed no structural differences between control-, RBH-, and BABA-treated plants after challenge.

Mucoromycotina 'fine root endophytes': a new molecular model for plant-fungal mutualisms?

The most studied plant-fungal symbioses to date are the interactions between plants and arbuscular mycorrhizal (AM) fungi of the Glomeromycotina clade. Advancements in phylogenetics and microbial community profiling have distinguished a group of symbiosis-forming fungi that resemble AM fungi as belonging instead to the Mucoromycotina. These enigmatic fungi are now known as Mucoromycotina 'fine root endophytes' and could provide a means to understand the origins of plant-fungal symbioses.

Epigenetic processes in plant stress priming: Open questions and new approaches.

Priming reflects the capacity of plants to memorise environmental stress experience and improve their response to recurring stress. Epigenetic modifications in DNA and associated histone proteins may carry short-term and long-term memory in the same plant or mediate transgenerational effects, but the evidence is still largely circumstantial. New experimental tools now enable scientists to perform targeted manipulations that either prevent or generate a particular epigenetic modification in a particular location of the genome.

A single amino acid transporter controls the uptake of priming-inducing beta-amino acids and the associated tradeoff between induced resistance and plant growth.

Selected β-amino acids, such as β-aminobutyric acid (BABA) and R-β-homoserine (RBH), can prime plants for resistance against a broad spectrum of diseases. Here, we describe a genome-wide screen of fully annotated Arabidopsis thaliana T-DNA insertion lines for impaired in RBH-induced immunity (iri) mutants against the downy mildew pathogen Hyaloperonospora arabidopsidis, yielding 104 lines that were partially affected and four lines that were completely impaired in RBH-induced resistance (IR). We confirmed the iri1-1 mutant phenotype with an independent T-DNA insertion line in the same gene, encoding the high-affinity amino acid transporter LYSINE HISTIDINE TRANSPORTER 1 (LHT1).

Immune priming in plants: from the onset to transgenerational maintenance.

Enhancing plant resistance against pests and diseases by priming plant immunity is an attractive concept for crop protection because it provides long-lasting broad-spectrum protection against pests and diseases. This review provides a selected overview of the latest advances in research on the molecular, biochemical and epigenetic drivers of plant immune priming. We review recent findings about the perception and signalling mechanisms controlling the onset of priming by the plant stress metabolite β-aminobutyric acid.

Long-Lasting Defence Priming by β-Aminobutyric Acid in Tomato Is Marked by Genome-Wide Changes in DNA Methylation.

Exposure of plants to stress conditions or to certain chemical elicitors can establish a primed state, whereby responses to future stress encounters are enhanced. Stress priming can be long-lasting and likely involves epigenetic regulation of stress-responsive gene expression. However, the molecular events underlying priming are not well understood.

Transcriptomic changes during the establishment of long-term methyl jasmonate-induced resistance in Norway spruce.

Norway spruce (Picea abies) is an economically and ecologically important tree species that grows across northern and central Europe. Treating Norway spruce with jasmonate has long-lasting beneficial effects on tree resistance to damaging pests, such as the European spruce bark beetle Ips typographus and its fungal associates. The (epi)genetic mechanisms involved in such long-lasting jasmonate induced resistance (IR) have gained much recent interest but remain largely unknown.

The genetic and epigenetic landscape of the centromeres.

Centromeres attach chromosomes to spindle microtubules during cell division and, despite this conserved role, show paradoxically rapid evolution and are typified by complex repeats. We used long-read sequencing to generate the Col-CEN genome assembly that resolves all five centromeres. The centromeres consist of megabase-scale tandemly repeated satellite arrays, which support CENTROMERE SPECIFIC HISTONE H3 (CENH3) occupancy and are densely DNA methylated, with satellite variants private to each chromosome.

Epigenetics: a catalyst of plant immunity against pathogens.

The plant immune system protects against pests and diseases. The recognition of stress-related molecular patterns triggers localised immune responses, which are often followed by longer-lasting systemic priming and/or up-regulation of defences. In some cases, this induced resistance (IR) can be transmitted to following generations.

The rise, fall and resurrection of chemical-induced resistance agents.

Since the discovery that the plant immune system could be augmented for improved deployment against biotic stressors through the exogenous application of chemicals that lead to induced resistance (IR), many such IR-eliciting agents have been identified. Initially it was hoped that these chemical IR agents would be a benign alternative to traditional chemical biocides. However, owing to low efficacy and/or a realization that their benefits sometimes come at the cost of growth and yield penalties, chemical IR agents fell out of favour and were seldom used as crop protection products.

The Induced Resistance Lexicon: Do's and Don'ts.

To be protected from biological threats, plants have evolved an immune system comprising constitutive and inducible defenses. For example, upon perception of certain stimuli, plants can develop a conditioned state of enhanced defensive capacity against upcoming pathogens and pests, resulting in a phenotype called 'induced resistance' (IR). To tackle the confusing lexicon currently used in the IR field, we propose a widely applicable code of practice concerning the terminology and description of IR phenotypes using two main phenotypical aspects: local versus systemic resistance, and direct versus primed defense responses.

The IBI1 Receptor of β-Aminobutyric Acid Interacts with VOZ Transcription Factors to Regulate Abscisic Acid Signaling and Callose-Associated Defense.

External and internal signals can prime the plant immune system for a faster and/or stronger response to pathogen attack. β-aminobutyric acid (BABA) is an endogenous stress metabolite that induces broad-spectrum disease resistance in plants. BABA perception in Arabidopsis is mediated by the aspartyl tRNA synthetase IBI1, which activates priming of multiple immune responses, including callose-associated cell wall defenses that are under control by abscisic acid (ABA).

Spodoptera frugiperda Caterpillars Suppress Herbivore-Induced Volatile Emissions in Maize.

The vast spectrum of inducible plant defenses can have direct negative effects on herbivores, or indirect effects, for instance in the form of herbivore-induced plant volatiles (HIPVs) that attract natural enemies. Various arthropods have evolved ways to suppress plant defenses. To test whether this is the case for caterpillar-induced HIPVs, we compared the volatile induction by Spodoptera frugiperda (Lepidoptera: Noctuidae), which is particularly well adapted to feed on maize (Zea mays), with the induction by three more generalist noctuid larvae.

Crying out for help with root exudates: adaptive mechanisms by which stressed plants assemble health-promoting soil microbiomes.

Plants employ immunological and ecological strategies to resist biotic stress. Recent evidence suggests that plants adapt to biotic stress by changing their root exudation chemistry to assemble health-promoting microbiomes. This so-called 'cry-for-help' hypothesis provides a mechanistic explanation for previously characterized soil feedback responses to plant disease, such as the development of disease-suppressing soils upon successive cultivations of take all-infected wheat.

Surviving in a Hostile World: Plant Strategies to Resist Pests and Diseases.

As primary producers, plants are under constant pressure to defend themselves against potentially deadly pathogens and herbivores. In this review, we describe short- and long-term strategies that enable plants to cope with these stresses. Apart from internal immunological strategies that involve physiological and (epi)genetic modifications at the cellular level, plants also employ external strategies that rely on recruitment of beneficial organisms.

An Adjustable Protocol to Analyze Chemical Profiles of Non-sterile Rhizosphere Soil.

The analysis of chemical diversity in non-sterile rhizosphere soil has been a pressing methodological challenge for years. Rhizosphere-enriched chemicals (, rhizochemicals) include root exudation chemicals, (microbial) breakdown products thereof, and produced metabolites by rhizosphere-inhabiting microbes, all of which can play an important role in plant-soil interactions. The power and resolution of analytical methods and statistical analysis pipelines allow for better acquisition, separation and identification of rhizochemicals, thus providing unprecedented insight into the biochemistry underpinning plant-soil interactions.

Bacterial infection systemically suppresses stomatal density.

Many plant pathogens gain entry to their host via stomata. On sensing attack, plants close these pores to restrict pathogen entry. Here, we show that plants exhibit a second longer term stomatal response to pathogens.

Metabolic regulation of the maize rhizobiome by benzoxazinoids.

The rhizobiome is an important regulator of plant growth and health. Plants shape their rhizobiome communities through production and release of primary and secondary root metabolites. Benzoxazinoids (BXs) are common tryptophan-derived secondary metabolites in grasses that regulate belowground and aboveground biotic interactions.

Identification and characterisation of hypomethylated DNA loci controlling quantitative resistance in .

Variation in DNA methylation enables plants to inherit traits independently of changes to DNA sequence. Here, we have screened an population of epigenetic recombinant inbred lines (epiRILs) for resistance against . These lines share the same genetic background, but show variation in heritable patterns of DNA methylation.