Biology subjects

Webb, A. A.

Publications and source records attributed to Webb, A. A..

10 recordsLinked to original sources

bioRxiv2026

The chromatin-associated PWO proteins interface with circadian and epigenetic signaling to regulate flowering time in Arabidopsis

Flowering time is a major determinant of reproductive success in plants and is regulated by several interconnected pathways which converge on few key flowering time-related genes. In the model plant Arabidopsis thaliana (Arabidopsis), both the circadian clock and chromatin-associated proteins integrate environmental cues to coordinate flowering (Staiger et al. 2013; Nohales and Kay, 2016; Du et al. 2019; Haider and Farrona, 2024). However, how the circadian-epigenetic signaling crosstalk regulates this crucial developmental transition has still been underexplored. PWWP-DOMAIN INTERACTORS OF POLYCOMBS 1 and 2 (PWO1 and PWO2) are chromatin-associated proteins that have been linked to the regulation of histone 2A (H2A) mono-ubiquitination (ub) (H2Aub) levels (Zheng et al. 2023). PWO1 and PWO2 also affect flowering time (Hohenstatt et al. 2018; Khan et al. 2026), but the underlying molecular mechanisms, their effects on clock genes, as well as their distinct contributions to flowering-time regulation remain mostly unknown.

plant biology↗

bioRxiv2026

Dim Green Light Enables Day-and-Night Monitoring of Leaf Movements

Understanding plant growth dynamics requires imaging across day-and-night cycles to quantify growth, movement and development in the aerial plant body and to capture the rhythmic nature of these processes. This requires imaging in light during the day and in darkness at night without perturbing plant physiology. Nighttime imaging has typically depended on infrared (IR) illumination, producing monochrome datasets that require specialised hardware and separate analysis pipelines when combined with daytime RGB imaging. Here, we evaluated very low-intensity green (dimG) illumination from standard LEDs as a practical alternative for colour-consistent nighttime imaging and assessed its physiological impact in Arabidopsis thaliana and Lactuca sativa (lettuce). We show that high resolution colour images can be obtained under dimG using low- cost cameras, with sufficient consistency between full-spectrum and dimG images to allow direct comparison and unified image analysis. We show that very low-fluence green light (<0.5 mol m-2 s-1) does not sustain circadian oscillations of gene activity under continuous exposure and does not perturb rhythms when applied during the dark phase of diel cycles. DimG imaging enabled accurate detection of diel leaf movement profiles in Arabidopsis circadian mutants, revealing genotype-specific phase differences under varying photoperiods. In lettuce, dimG pulses and continuous dimG enabled accurate quantification of diel leaf movement without affecting growth, stomatal opening, electron transport rate or chlorophyll content. Motion profiles under continuous dimG mirrored those under darkness. Our findings establish dim green illumination as a cost-effective solution for night-time imaging, simplifying phenotyping workflows with minimal impact on physiology.

plant biology↗

bioRxiv2025

Data-driven mathematical modelling explains altered timing of EARLY FLOWERING 3 in the wheat circadian oscillator

Circadian rhythms, daily oscillations with a free-running period of approximately 24 hours, have evolved in organisms across the kingdoms of life, enabling organisms to anticipate and adapt to environmental cycles. Circadian timing in plants is governed by an oscillator gene network of transcriptional regulators that exists in each cell. Wheat provides an opportunity to investigate the mechanisms of the plant circadian oscillator in an important agricultural species. We recently found that a single oscillator component EARLY FLOWERING 3 is expressed at a different time in wheat compared to the model plant Arabidopsis. This was unexpected since there is remarkable conservation of timing of activity of the different oscillator components within a kingdom, for example, even when animals switch from nocturnal to diurnal activity. We have examined how the change in timing of ELF3 transcription between Arabidopsis and wheat has occurred and its implications for circadian oscillator function. We describe an optimised computational model of the wheat circadian oscillator that is informed by experimental data and the structure of the promoter elements driving oscillator gene expression. Our optimised computational models suggest that the dawn-expression of the key oscillator gene ELF3 in wheat occurs due to repression of the ELF3 promoter by TOC1. Our simulations predict that plant circadian oscillators are robust against changes in ELF3 timing. Our work demonstrates that plant circadian oscillators can have a flexible architecture such that different oscillator structures can originate circadian rhythms.

plant biology↗

bioRxiv2025

Arbor function of TRANSPARENT TESTA GLABRA 1 and LIGHT REGULATED WD scaffold proteins in the Arabidopsis circadian oscillators includes transcriptional repression through PSEUDO RESPONSE REGULATORS

Arabidopsis circadian oscillators contain DNA-binding proteins that function at specific times of day. In contrast, we have discovered a continuous function of WD40-repeat scaffold proteins from the TRANSPARENT TESTA GLABRA-1 (TTG1), LIGHT REGULATED WD1 and LIGHT REGULATED LWD2 subfamily (TLWD) which is essential to maintain circadian rhythms. Gene expression analyses indicate multifunctional activity of TLWD in both transcriptional activation and repression. TLWD proteins interact with an array of circadian oscillator activators and repressors that act sequentially throughout the diel cycle. While TLWD proteins were known to participate in activator complexes, our data indicate a novel role of TLWD in transcriptional repression through complex formation with repressors from the PSEUDO RESPONSE REGULATOR (PRR) family. In an analogy to mechanical clocks, TLWD scaffold proteins constitute an ever-present arbor, or spindle, to which transcription factors, which represent the cogs, bind to sustain circadian rhythms.

plant biology↗

bioRxiv2024

GIGANTEA is required for circadian rhythms in wheat

GIGANTEA (GI) is a plant-specific protein that functions in many physiological processes and signalling networks. In Arabidopsis, GI has a central role in circadian oscillators regulating the abundance of ZEITLUPE and TIMING OF CAB EXPRESSION 1 proteins and is essential for photoperiodic regulation of flowering. We have investigated how ortholgues of this component of Arabidopsis circadian oscillators contributes to circadian rhythms and yield traits, including heading (flowering) in wheat. We find that GI is a core component of wheat circadian oscillators that is necessary to maintain robust oscillations in chlorophyll fluorescence and circadian oscillator transcript abundance. Predicted lack of functional GI results in later flowering in wheat in both long days and short days in controlled environment conditions. Our results support and extend previous work which suggests that the pathways by which photoperiodism regulates flowering are not fully conserved between Arabidopsis and wheat. Understanding the molecular basis for photoperiodism in wheat is important for breeders looking to manipulate flowering time and develop new elite, high yielding cultivars. HighlightGIGANTEA is required for robust circadian oscillations in wheat and regulates heading, most likely through a PHOTOPERIOD-1-dependent pathway.

plant biology↗

bioRxiv2023

Compartmentation of photosynthesis gene expression between mesophyll and bundle sheath cells of C4 maize is dependent on time of day

Compared with the ancestral C3 state, C4 photosynthesis enables higher rates of photosynthesis as well as improved water and nitrogen use efficiencies. In both C3 and C4 plants rates of photosynthesis increase with light intensity and so are maximal around midday. We report that in the absence of light or temperature fluctuations, photosynthesis in maize peaks in the middle of the subjective photoperiod. To investigate molecular processes associated with these changes, we undertook RNA-sequencing of maize mesophyll and bundle sheath strands over a 24-hour time-course. Cell-preferential expression of C4 cycle genes was strongest between six and ten hours after dawn when rates of photosynthesis were highest. For the bundle sheath, DNA motif enrichment and gene co-expression analyses suggested members of the DOF and MADS-domain transcription factor families mediate diurnal fluctuations in C4 gene expression, and trans-activation assays in planta confirmed their ability to activate promoter fragments from bundle sheath expressed genes. The work thus identifies transcriptional regulators as well as peaks in cell-specific C4 gene expression coincident with maximum rates of photosynthesis in the maize leaf at midday.

plant biology↗

bioRxiv2022

Overexpression of the WAPO-A1 gene increases the number of spikelets per spike in bread wheat

Two homoeologous QTLs for number of spikelets per spike (SPS) were mapped on chromosomes 7AL and 7BL using two wheat MAGIC populations. Sets of lines contrasting for the QTL on 7AL were developed which allowed for the validation and fine mapping of the 7AL QTL and for the identification of a previously described candidate gene, WHEAT ORTHOLOG OF APO1 (WAPO1). Using transgenic overexpression in both a low and a high SPS line, we provide a functional validation for the role of this gene in determining SPS also in hexaploid wheat. We show that the expression levels of this gene positively correlate with SPS in multiple MAGIC founder lines under field conditions as well as in transgenic lines grown in the greenhouse. This work highlights the potential use of WAPO1 in hexaploid wheat for further yield increases. The impact of WAPO1 and SPS on yield depends on other genetic and environmental factors, hence, will require a finely balanced expression level to avoid the development of detrimental pleiotropic phenotypes.

plant biology↗

bioRxiv2020

Ribosomes act as cryosensors in plants

Cold temperatures are a threat to temperate plants, and Arabidopsis thaliana has acquired an adaptive gene expression network controlled by CBF transcription factors. The CBFs are sufficient to enable plants to survive otherwise lethal subzero temperatures. Constitutive CBF expression causes delayed flowering and stunted growth, and plants have evolved the ability to restrict CBF expression to occur only in the cold. This allows plants to anticipate likely freezing events and selectively deploy cold tolerance. The mechanism by which cold stress is sensed is however unknown. Here we show that protein translation rates in plants are proportional to temperature, and reduced translation rates trigger a rise in intracellular free calcium that activates the CAMTA transcription factors, and these directly activate cold-induced gene expression.

plant biology↗

bioRxiv2020

Magnesium maintains length of circadian period in Arabidopsis thaliana

The circadian clock coordinates the physiological response of a biological system to day and night rhythms through complex loops of transcriptional/ translational regulation. It can respond to external stimuli and adjust generated circadian oscillations accordingly to keep an endogenous period close to 24 h. To date, the interaction between nutritional status and circadian rhythms in plants is poorly understood. Magnesium (Mg) is essential for numerous biological processes in plants and its homeostasis is crucial to maintain optimal development and growth. Magnesium deficiency in young Arabidopsis thaliana seedlings increased the circadian period of pCCA1:LUC oscillations and dampened its amplitude in constant light in a dose-dependent manner. Although circadian period increase by Mg deficiency was light dependent, it did not depend on active photosynthesis. Mathematical modelling of the Mg input to the circadian clock reproduced the experimental increase of the circadian period and suggested that Mg is likely to affect global transcription/translation levels rather than a single component of the circadian oscillator. The model prediction was supported by a synergistic interaction between Mg deficiency and cyclohexamide, an inhibitor of translation. These findings suggest that proper Mg supply is required to support proper timekeeping in plants. One sentence summaryMagnesium maintains the circadian period in Arabidopsis seedlings and interferes with the circadian oscillator most likely through translational mechanisms.

molecular biology↗

bioRxiv2019

Differential effects of day-night cues and the circadian clock on the barley transcriptome

The circadian clock is a complex transcriptional network that regulates gene expression in anticipation of the day-night cycle and controls agronomic traits in plants. However, in crops, information on the effects of the internal clock and day-night cues on the transcriptome is limited. We analysed the diel and circadian leaf transcriptomes in the barley cultivar Bowman and derived introgression lines carrying mutations in EARLY FLOWERING 3 (ELF3), LUX1, and EARLY MATURITY 7 (EAM7). Mutations in ELF3 and LUX1 abolished circadian transcriptome oscillations under constant conditions, whereas eam7 maintained oscillations of {approx}30% of the circadian transcriptome. However, day-night cues fully restored transcript oscillations in all three mutants and thus compensated for a disrupted oscillator in the arrhythmic barley clock mutants elf3 and lux1. Nevertheless, elf3 but not lux1 affected the phase of the diel oscillating transcriptome and thus the integration of external cues into the clock. Using dynamical modelling, we predicted a structure of the barley circadian oscillator and interactions of its individual components with day-night cues. Our findings provide a valuable resource for exploring the function and output targets of the circadian clock and for further investigations into the diel and circadian control of the barley transcriptome.

plant biology↗