Biology subjects

Osborne, R.

Publications and source records attributed to Osborne, R..

5 recordsLinked to original sources

bioRxiv2026

Symbiont effectors modulate plant signalling to increase host stress resilience

Plant colonizing mutualistic symbionts confer beneficial effects to their hosts, which often includes increased growth, and biotic and abiotic stress resilience. How these benefits are activated on a molecular level is mostly unknown. Here, we describe effector candidates of the fungal symbiont Serendipita indica (Si), which modulate plant stress signalling pathways. By analyzing the Si effector interactome, we reveal frequent targeting of stress related host proteins, which are linked to the identified effector signalling functions. Moreover, functional data indicate that Si effectors modulate abiotic stress response of Arabidopsis, as well as resistance to pathogen infection. Analysis of symbiont effectors might not only uncover previously unreported molecular mechanisms that increase plant fitness but might also be used to identify potential genetic traits for crop improvement under changing climates.

plant biology↗

bioRxiv2026

An oxygen-sensing Polycomb-group protein encodes flooding stress memory in plants

Most organisms, including plants, can encode stress memories that improve resilience to repeated environmental challenges. Flooding events expose plants to recurrent hypoxia, yet whether plants establish an adaptive memory of flooding is unclear. Here we show that somatic flooding stress memory is a conserved feature across multiple angiosperm species. In Arabidopsis, this memory depends on the oxygen-sensitive Polycomb Repressive Complex 2 (PRC2) subunit VERNALIZATION2 (VRN2). Loss of VRN2 impairs epigenetic memory formation and disrupts transcriptional memory at key genes that promote anthocyanin accumulation and repress leaf senescence, adaptive responses that enhance flooding tolerance. Collectively, we reveal a molecular mechanism where VRN2-PRC2 acts as both an oxygen sensor and chromatin effector to establish adaptive flooding stress memory in plants. ShortOur work defines a molecular mechanism for flooding stress memory in plants, actioned via the PRC2 subunit VRN2, that acts as the direct molecular (low) oxygen sensor and transducer. Coupled to its role in cold sensing, this identifies VRN2 as a master sensor subunit of the plant PRC2 that integrates multiple environmental cues to modulate the chromatin landscape and encode environmental memory.

plant biology↗

bioRxiv2024

VRN2-PRC2 facilitates light-triggered repression of PIF signalling to coordinate growth in Arabidopsis

The polycomb protein VERNALIZATION2 (VRN2) is a plant-specific subunit of the polycomb repressive complex 2 (PRC2), a conserved eukaryotic holoenzyme that represses gene expression by depositing the histone H3K27me3 mark in chromatin. Previous work established VRN2 as an oxygen-regulated target of the N-degron pathway that may function as a sensor subunit connecting PRC2 activity to the perception of positional and environmental cues. Here we show that VRN2 is enriched in hypoxic meristematic regions and emerging leaves of Arabidopsis under non-stressed conditions, and that vrn2 mutants are larger than wild type, indicating that VRN2-PRC2 negatively regulates growth and development. This growth phenotype is caused by ectopic expression of genes that promote cell expansion, including many SAUR genes and other direct PIF transcription factor targets. Analysis of SAUR19 promoter activity and expression dynamics revealed that VRN2 is required to specifically repress these genes in the light. Moreover, we show that VRN2 is epistatic to PIF4, and directly binds and methylates histones of key loci in the PIF4 transcriptional network to provide robust light-responsive control of gene expression and growth. We propose that hypoxia-stabilised VRN2-PRC2 sets a conditionally repressed chromatin state at PIF-regulated hub genes early in leaf ontogeny coinciding with the cell division phase, and that this is required for enhancing their subsequent repression via a light-responsive signalling cascade as cells enter the expansion phase. Thus, we have identified VRN2-PRC2 as core component of a spatially regulated and developmentally encoded epigenetic mechanism that co-ordinates environment-responsive growth by facilitating light-triggered suppression of PIF signalling.

plant biology↗

bioRxiv2021

Genome-wide mutational signatures of immunological diversification in normal lymphocytes

A lymphocyte suffers many threats to its genome, including programmed mutation during differentiation, antigen-driven proliferation and residency in diverse microenvironments. After developing protocols for single-cell lymphocyte expansions, we sequenced whole genomes from 717 normal naive and memory B and T lymphocytes and hematopoietic stem cells. Lymphocytes carried more point mutations and structural variation than stem cells, accruing at higher rates in T than B cells, attributable to both exogenous and endogenous mutational processes. Ultraviolet light exposure and other sporadic mutational processes generated hundreds to thousands of mutations in some memory lymphocytes. Memory B cells acquired, on average, 18 off-target mutations genome-wide for every one on-target IGV mutation during the germinal center reaction. Structural variation was 16-fold higher in lymphocytes than stem cells, with ~15% of deletions being attributable to off-target RAG activity. One Sentence SummaryThe mutational landscape of normal lymphocytes chronicles the off-target effects of programmed genome engineering during immunological diversification and the consequences of differentiation, proliferation and residency in diverse microenvironments.

genomics↗

bioRxiv2020

The Arabidopsis NOT4A E3 ligase coordinates PGR3 expression to regulate chloroplast protein translation

Chloroplast function requires the coordinated action of nuclear- and chloroplast-derived proteins, including several hundred nuclear-encoded pentatricopeptide repeat (PPR) proteins that regulate plastid mRNA metabolism. Despite their large number and importance, regulatory mechanisms controlling PPR expression are poorly understood. Here we show that the Arabidopsis NOT4A ubiquitin-ligase positively regulates PROTON GRADIENT 3 (PGR3), a PPR protein required for translating 30S ribosome subunits and several thylakoid-localised photosynthetic components within chloroplasts. Loss of NOT4A function leads to a strong depletion of plastid ribosomes, which reduces mRNA translation and negatively impacts photosynthetic capacity, causing pale-yellow and slow-growth phenotypes. Quantitative transcriptome and proteome analyses reveal that these defects are due to a lack of PGR3 expression in not4a, and we show that normal plastid function is restored through transgenic PGR3 expression. Our work identifies NOT4A as crucial for ensuring robust photosynthetic function during development and stress-response, through modulating PGR3 levels to coordinate chloroplast protein synthesis.

plant biology↗