Biology subjects

Haydon, M. J.

Publications and source records attributed to Haydon, M. J..

6 recordsLinked to original sources

bioRxiv2025

Redox-controlled dimerisation regulates ethylene biosynthesis

Ethylene is a central plant hormone that orchestrates growth, development, senescence, and stress responses. Because it is gaseous, ethylene must be synthesised on demand, yet the catalytic and regulatory mechanisms of its biosynthetic enzyme, 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), remain poorly understood. Here, using structural, biophysical, and computational analyses, we uncovered two principles: ACO catalysis relies on an induced-fit mechanism, and disulfide-mediated dimerisation via a conserved cysteine acts as a redox switch toggling ACO between active monomer and inactive dimer. This previously unrecognised regulatory layer positions ACO as a redox sensor in plant cells, revealing a fundamental control point in ethylene biosynthesis. Given ethylenes pivotal role in crop productivity and stress resilience, these findings open new opportunities for precise manipulation of hormone signalling in agriculture and biotechnology.

biochemistry↗

bioRxiv2025

A non-coding SNP in ELF3 alters expression of ELF3β and confers adaptation of Arabidopsis to a continental climate

Circadian clocks are biological timekeepers that influence most aspects of plant biology and allow organisms to predict and adapt to daily and seasonal environmental cycles. In particular, the important role of circadian clocks in phenology has led to numerous examples of both functional variation in circadian clock genes within natural and domesticated plant populations. To assess variation of circadian rhythms in natural Arabidopsis populations, we have phenotyped 287 accessions using a seedling transformation protocol with a circadian luciferase reporter. A genome wide association study of circadian period identified multiple single nucleotide polymorphisms (SNPs) in the core clock gene EARLY FLOWERING 3 (ELF3). We identified three ELF3 haplogroups that are associated with seasonal variability in temperature found in continental climates and found strong evidence of a selective sweep coinciding with the most recent de-glaciation period in Europe. One of the SNPs is located within intron 2 of ELF3 in the region upstream of an alternative transcription start site affecting expression of a shorter ELF3{beta} transcript. Our results indicate the important role of subtle variation in a core circadian clock gene in adaptation to changing climate.

plant biology↗

bioRxiv2024

A circadian transcriptional sub-network and EARLY FLOWERING 3 control timing of senescence and grain nutrition in bread wheat

Circadian clocks control daily and seasonal timing of physiology and development. Because of their influence on photoperiodic flowering, variants in circadian clock genes have been selected for phenology during domestication of cereal crops. To explore the potential impact of this genetic variation on circadian-regulated traits, we investigated the relationship of the circadian clock and leaf senescence in hexaploid bread wheat. Phenotyping of a collection of elite wheat cultivars identified significant variation in circadian rhythms which was associated with timing of senescence and nutrient mobilisation efficiency. RNA sequencing revealed substantial reorganisation of the circadian-regulated transcriptome during senescence and a transcriptional sub-network representing a link between the circadian oscillator and regulators of leaf senescence. We used genotypes of multiple circadian clock genes to assign cultivars to chronotypes, which could be used to predict circadian-regulated phenotypes. This identified a deletion variant of EARLY FLOWERING 3-D1 (ELF3-D1) attributed to a phenology locus, Earliness per se (Eps-D1), and we used near-isogenic lines (NILs) to show that it affects timing of senescence and grain protein content (GPC). Thus, there are potential consequences of circadian clock genes selected for phenology on other valuable crop traits.

plant biology↗

bioRxiv2023

Guidelines for performing ribosome profiling in plants including structural analysis of rRNA fragments

Ribosome profiling (or Ribo-seq) is a technique that provides genome-wide information on the translational landscape (translatome). Across different plant studies, variable methodological setups have been described which raises questions about the general comparability of data that were generated from diverging methodologies. Furthermore, a common problem when performing Ribo-seq are abundant rRNA fragments that are wastefully incorporated into the libraries and dramatically reduce sequencing depth. To remove these rRNA contaminants, it is common to perform preliminary trials to identify these fragments because they are thought to vary depending on nuclease treatment, tissue source, and plant species. Here, we compile valuable insights gathered over years of generating Ribo-seq datasets from different species and experimental setups. We highlight which technical steps are important for maintaining cross experiment comparability and describe a highly efficient approach for rRNA removal. Furthermore, we provide evidence that many rRNA fragments are structurally preserved over diverse nuclease regimes, as well as across plant species. Using a recently published cryo-electron microscopy (cryo-EM) structure of the tobacco 80S ribosome, we show that the most abundant rRNA fragments are spatially derived from the solvent-exposed surface of the ribosome. The guidelines presented here shall aid newcomers in establishing ribosome profiling in new plant species and provide insights that will help in customizing the methodology for individual research goals.

plant biology↗

bioRxiv2021

A ROS-Ca2+ signalling pathway identified from a chemical screen for modifiers of sugar-activated circadian gene expression.

Sugars are essential metabolites for energy and anabolism that can also act as signals to regulate plant physiology and development. Experimental tools to disrupt major sugar signalling pathways are limited. We have performed a chemical screen for modifiers of activation of circadian gene expression by sugars to discover pharmacological tools to investigate and manipulate plant sugar signalling. Using a library of commercially available bioactive compounds, we identified 75 confident hits that modified the response of a circadian luciferase reporter to sucrose in dark-adapted seedlings. We validated the transcriptional effect on a subset of the hits and measured their effects on a range of sugar-dependent phenotypes for 13 of these chemicals. Chemicals were identified that appear to influence known and unknown sugar signalling pathways. Pentamidine isethionate (PI) was identified as a modifier of a sugar-activated Ca2+ signal that acts downstream of superoxide in a metabolic signalling pathway affecting circadian rhythms, primary metabolism and plant growth. Our data provide a resource of new experimental tools to manipulate plant sugar signalling and identify novel components of these pathways.

plant biology↗

bioRxiv2021

Root-to-shoot iron partitioning in Arabidopsis requires IRON-REGULATED TRANSPORTER1 (IRT1)

IRON-REGULATED TRANSPORTER1 (IRT1) is the root high-affinity ferrous iron uptake system and indispensable for the completion of the life cycle of Arabidopsis thaliana without vigorous iron (Fe) supplementation. Here we provide evidence supporting a second role of IRT1 in root-to-shoot mobilization of Fe. We show that the irt1-2 (pam42) mutant over-accumulates Fe in roots, most prominently in the cortex of the differentiation zone, when compared to the wild type. Shoots of irt1-2 are severely Fe-deficient according to Fe content and marker transcripts, as expected. We generated irt1-2 lines producing IRT1 mutant variants carrying single amino-acid substitutions of key residues in transmembrane helices IV and V, Ser206 and His232, which are required for transport activity in yeast. In the transgenic Arabidopsis lines, short-term root Fe uptake rates and secondary substrate Mn accumulation resemble those of irt1-2, suggesting that these plants remain incapable of IRT1-mediated root Fe uptake. Yet, IRT1S206A partially complements rosette dwarfing and leaf chlorosis, as well as root-to-shoot Fe partitioning and gene expression defects of irt1-2, all of which are fully complemented by wild-type IRT1. Taken together, these results suggest a function for IRT1 in root-to-shoot Fe partitioning that does not require Fe transport activity of IRT1. Among the genes of which transcript levels are partially dependent on IRT1, we identify MYB DOMAIN PROTEIN10, MYB DOMAIN PROTEIN72 and NICOTIANAMINE SYNTHASE4 as candidates for effecting IRT1-dependent Fe mobilization in roots. Understanding the biological functions of IRT1 will help to improve iron nutrition and the nutritional quality of agricultural crops.

plant biology↗