Biology subjects

Knappe, C.

Publications and source records attributed to Knappe, C..

5 recordsLinked to original sources

bioRxiv2026

Pseudomonas simiae-induced resistance in barley is associated with compromised JA signaling and phyllosphere microbiome responses

Interactions of plant growth-promoting rhizobacteria with plant roots can trigger induced resistance (IR) protecting above-ground tissues from disease, a process that is increasingly recognized for its potential to support sustainable crop protection strategies. Although the molecular basis of IR has been extensively studied in Arabidopsis thaliana, considerably less is known about the underlying mechanisms in cereal crops. Here, we show that Pseudomonas simae WCS417r triggers IR in barley (Hordeum vulgare), reducing the propagation of Blumeria graminis f. sp. hordei, the causative agent of barley powdery mildew. Analysis of defense-associated marker genes revealed pathogen-dependent transcriptional responses during IR: HvPATHOGENESIS-RELATED1 (HvPR1) was induced by powdery mildew but not by the bacterial pathogen Xanthomonas translucens pathovar cerealis, whereas HvPR5 responded to both pathogens, with its induction by X. translucens depending on WCS417r-IR. To improve our molecular understanding of IR, transcriptomic responses to methyl jasmonate, salicylic acid and abscisic acid were characterized and used to identify hormone-responsive genes. Notably, several jasmonate-responsive genes were suppressed during powdery mildew infection, and this suppression was more pronounced in plants undergoing IR, indicative of priming. Finally, metabarcoding of the phyllosphere microbiome demonstrated that IR was not associated with major shifts in bacterial community composition. Alpha and beta diversity remained largely unchanged, while a limited number of amplicon sequence variants differed in abundance between treatments. Together, these results show that P. simiae WCS417r induces resistance against powdery mildew in barley through priming pathogen-dependent transcriptional changes while leaving the overall phyllosphere microbiome structure largely intact.

plant biology↗

bioRxiv2022

Part-night exposure to artificial light at night has more detrimental effects on aphid colonies than fully lit nights

Artificial light at night (ALAN) threatens natural ecosystems globally. While ALAN research is increasing, little is known about how ALAN affects plants and interactions with other organisms. We explored the effects of ALAN on plant defence and plant-insect interactions using barley (Hordeum vulgare) and the English grain aphid (Sitobion avenae). Plants were exposed to full or part nights of 15-20 lux ALAN, or no ALAN control nights, to test the effects of ALAN on plant growth and defence. Although plant growth was only minimally affected by ALAN, aphid colony growth and aphid maturation were reduced significantly by ALAN treatments. Importantly, we found strong differences between full-night and part-night ALAN treatments. Contrary to our expectations, part ALAN had stronger negative effects on aphid colony growth than full ALAN. Defence-associated gene expression was affected in some cases by ALAN, but also positively correlated with aphid colony size, suggesting that the effects of ALAN on plant defences are indirect, and regulated via direct disruption of aphid colonies, rather than via ALAN-induced upregulation of defences. Mitigating ecological side effects of ALAN is a complex problem, as reducing exposure to ALAN increased its negative impact on insect herbivores.

ecology↗

bioRxiv2022

3D-surface reconstruction of cellular cryo-soft X-ray microscopy tomograms using semi-supervised deep learning

Cryo-soft X-ray tomography (cryo-SXT) is a powerful method to investigate the ultrastructure of cells, offering resolution in the tens of nm range and strong contrast for membranous structures without requirement for labeling or chemical fixation. The short acquisition time and the relatively large volumes acquired allow for fast acquisition of large amounts of tomographic image data. Segmentation of these data into accessible features is a necessary step in gaining biologically relevant information from cryo-soft X-ray tomograms. However, manual image segmentation still requires several orders of magnitude more time than data acquisition. To address this challenge, we have here developed an end-to-end automated 3D-segmentation pipeline based on semi-supervised deep learning. Our approach is suitable for high-throughput analysis of large amounts of tomographic data, while being robust when faced with limited manual annotations and variations in the tomographic conditions. We validate our approach by extracting three-dimensional information on cellular ultrastructure and by quantifying nanoscopic morphological parameters of filopodia in mammalian cells.

bioinformatics↗

bioRxiv2021

Local jasmonic acid cues drive systemic acquired resistance signal generation

The phytohormones salicylic acid (SA) and jasmonic acid (JA) promote two, mutually antagonistic immune pathways respectively protecting plants from biotrophic pathogens and necrotrophic pathogens or insects. This trade-off largely precludes the exploitation of SA and JA immune components for crop protection, raising the interest in immune signalling components that disrupt SA-JA antagonism. A local pathogen infection primes SA-dependent immunity in systemic tissues. This so-called systemic acquired resistance (SAR) ensures a long-lasting, broad-spectrum disease resistance that is not subject to SA-JA antagonism. Here, we show that two sequence-related LEGUME LECTIN-LIKE PROTEINs (LLPs) promote SAR through spatially separated functions with JA promoting local SAR signal generation through LLP3. In concert with LLP1, which is important for systemic recognition and propagation of SAR signals, LLP3 promotes both SA-dependent SAR and JA-mediated immunity. Thus, exploitation of LLP-associated signalling cues might allow application of plant innate immune signals to promote (crop) plant health.

plant biology↗

bioRxiv2021

Induced systemic resistance impacts the phyllosphere microbiome through plant-microbe-microbe interactions

Both above- and below-ground parts of plants are constantly confronted with microbes, which are main drivers for the development of plant-microbe interactions. Plant growth-promoting rhizobacteria enhance the immunity of above-ground tissues, which is known as induced systemic resistance (ISR). We show here that ISR also influences the leaf microbiome. We compared ISR triggered by the model strain Pseudomonas simiae WCS417r (WCS417) to that triggered by Bacillus thuringiensis israelensis (Bti) in Arabidopsis thaliana. In contrast to earlier findings, immunity elicited by both strains depended on salicylic acid. Both strains further relied on MYC2 for signal transduction in the plant, while WCS417-elicited ISR additionally depended on SAR-associated metabolites, including pipecolic acid. A metabarcoding approach applied to the leaf microbiome revealed a significant ISR-associated enrichment of amplicon sequence variants with predicted plant growth-promoting properties. WCS417 caused a particularly dramatic shift in the leaf microbiota with more than 50% of amplicon reads representing two bacterial species: WCS417 and Flavobacterium sp.. Co-inoculation experiments using WCS417 and At-LSPHERE Flavobacterium sp. Leaf82, suggest that the proliferation of these bacteria is influenced by both microbial and plant-derived factors. Together, our data connect systemic immunity with leaf microbiome dynamics and highlight the importance of plant- microbe-microbe interactions for plant health.

plant biology↗