Biology subjects

Bennett, T.

Publications and source records attributed to Bennett, T..

12 recordsLinked to original sources

bioRxiv2025

Structural and functional characterisation of a reconstructed ancestral strigolactone receptor

Strigolactones are phytohormones that regulate shoot branching and promote root interactions with arbuscular mycorrhizal fungi. In seed plants, strigolactone perception begins with the enzyme-receptor DWARF14 (D14), an /{beta}-hydrolase that is believed to have evolved via gene duplication from the karrikin receptor, KARRIKIN INSENSITIVE2 (KAI2). D14 and KAI2 are highly homologous at the sequence and structural levels, and both proteins bind and cleave similar butenolide compounds. Nevertheless, the two signalling pathways are distinct, as the activity of one receptor cannot compensate for the loss of the other. Here, we apply ancestral sequence reconstruction to generate a D14 protein representative of seed plants to study the evolution of substrate specificity, and to explore desirable traits for protein engineering. We describe the structure, as well as the in vitro and in planta activity of ancestral D14, showing that substrate specificity does not meaningfully differ from that of Arabidopsis thaliana D14. We also demonstrate that ancestral D14 shows higher recombinant yields, greatly increased thermostability, and enhanced catalytic activity relative to D14 from A. thaliana. This work provides insight into the evolution of phytohormone signalling and presents a robust scaffold for the application of D14-type proteins in synthetic biology. SIGNIFICANCE STATEMENTAncestral sequence reconstruction of the strigolactone receptor DWARF14 (D14) reveals that its substrate specificity has remained largely conserved in seed plants. Additionally, the ancestral reconstruction exhibits superior recombinant yields, thermostability, and catalytic activity relative to Arabidopsis thaliana D14, providing both evolutionary insights and promising utility for synthetic biology applications.

plant biology↗

bioRxiv2025

Wheat - black-grass competition is a non-zero-sum game influenced by root growth

Interactions with neighbouring plants have profound effects on plant growth, especially in crop-weed interactions, which can cause major crop-losses in agricultural systems. Black-grass (Alopecurus myosuroides) is the most problematic weed for UK agriculture, causing dramatic yield losses in winter wheat, but the basis of its competitive advantage is not clear. We aimed to fundamentally reappraise the nature of wheat - black-grass competition. Here, we show that black-grass is slow to establish, and requires long periods to demonstrate any competitive advantage over wheat. We show that black-grass grows significantly faster under winter conditions than wheat, and has much more vigorous root growth, collectively suggesting that prolonged root growth over winter is key to black-grasss competitive advantage over wheat. We tested the competitiveness of a range of wheat and barley germplasm against black-grass in three distinct environmental set-ups, and show that competitiveness under controlled conditions reflects competitiveness under field conditions. In controlled conditions, we identified significant variation in crop varietal competitiveness against black-grass, in both ability to suppress black-grass growth, and to continue to grow in the presence of black-grass (tolerance). We further identified that this competition is not a zero-sum game, with loss in crop biomass not necessarily equal to gain in black-grass biomass. Finally, we found that the black-grass suppression, but not tolerance, is correlated with crop root growth, supporting our root growth hypothesis for black-grass competition. Overall, our results suggest that breeding for increased root growth and/or winter growth rate can create more competitive wheat cultivars for grassweed suppression.

plant biology↗

bioRxiv2025

Cytokinin overcomes spikelet-driven inhibition of tillering in wheat and barley by delaying meristem development

Correlative inhibition mechanisms allow plants to regulate the number of organs they produce, but act as a developmental limitation on crop yields. Previously, trade-offs have been observed in wheat and barley between the size of individual compound inflorescences (spikes) and the total number of spikes produced by each plant. We aimed to test the hypothesis that these trade-offs represent an uncharacterized form of correlative inhibition in grass reproductive architecture. We show that high spikelet lines with spikes containing enhanced numbers of spikelets have reduced tillering and retarded development of later-initiated spikes. Moreover, we show that this effect is driven by the presence of developing, but not mature, spikelets in early-initiated spikes, thus representing a form of correlative inhibition. We show that cytokinin treatment delays the development of spike meristems and formation of spikelets, and as such, can promote the development of additional spikes in high spikelet lines, by providing a longer window for tillering to occur. Our results thus identify cytokinin as a potential target for breeding crops with enhanced yield. Furthermore, our results provide a developmental basis for previously observed yield trade-offs in cereal crops, and illustrate the importance of understanding developmental timing when attempting to breed higher-yielding crops.

plant biology↗

bioRxiv2023

Strigolactones optimise plant water usage by modulating vessel formation

Wood formation is fundamental for the remarkable growth of plant bodies by continuously providing cells for long-distance transport of water and nutrients1-3. Vessel elements, the water transporting units within woody tissues, are generated from a cylindrical domain of cambium stem cells (CSCs) producing different vascular cell types in a bidirectional manner4-6. However, knowledge on the regulation of CSC activity is limited with unclear cell fate trajectories as the most obscure aspect in this context. Here, via revealing transcriptome signatures of CSCs and their derivatives with single cell resolution in Arabidopsis thaliana, we discover that the strigolactone (SL) signalling pathway modulates cell type composition in vascular tissues and thereby increases drought resistance. In particular, we find that SL signalling negatively regulates vessel element formation and thereby plant water usage. SL signalling is generally associated with differentiating vascular tissues but low in developing vessels and in CSCs implying a local role during fate decisions in CSC-derived cells. Highlighting the importance of vascular tissue composition for the overall plant water balance, alteration of vessel element formation has a direct impact on transpiration rates through leaf stomata. Our results demonstrate the importance of structural alignment of water transporting tissues to unstable water regimes and provide perspectives for a long-term modulation of drought resistance in plants.

plant biology↗

bioRxiv2022

Cytokinin signalling regulates two-stage inflorescence arrest in Arabidopsis

To maximise their reproductive success, flowering plants must correctly time their entry into and exit from the reproductive phase (flowering). While much is known about the mechanisms that regulate the initiation of flowering, the regulation of end-of-flowering remains largely uncharacterised. End-of-flowering in Arabidopsis thaliana consists of the quasi-synchronous arrest of individual inflorescences, but it is unclear how this arrest is correctly timed with respect to environmental stimuli and ongoing reproductive success. Here we show that Arabidopsis inflorescence arrest is a complex developmental phenomenon which includes a decline in size and cessation of activity in the inflorescence meristem (IM), coupled with a separable developmental arrest in all unopened floral primordia (floral arrest); these events occur well before the visible arrest of the inflorescence. We show that global removal of inflorescences can delay both IM arrest and floral arrest, but that local fruit removal only delays floral arrest, emphasising the separability of these processes. We test a role for cytokinin in regulating inflorescence arrest, and find that cytokinin treatment can delay arrest. We further show that gain-of-function cytokinin receptor hypersensitive mutants can delay floral arrest, and also IM arrest, depending on the expression pattern of the receptor; conversely, loss-of-function mutants prevent extension of flowering in response to inflorescence removal. Collectively, our data suggest that the dilution of cytokinin among an increasing number of sink organs leads to end-of-flowering in Arabidopsis by triggering IM and floral arrest, conversely meaning that a lack of reproductive success can homeostatically extend flowering in compensation.

plant biology↗

bioRxiv2021

KAI2 regulates seedling development by mediating light-induced remodelling of auxin transport

The photomorphogenic remodelling of seedling growth upon exposure to light is a key developmental transition in the plant life cycle. The /{beta}-hydrolase signalling protein KARRIKIN-INSENSITIVE2 (KAI2), a close homologue of the strigolactone receptor DWARF14 (D14), is involved in this process, and kai2 mutants have strongly altered seedling growth as a result1. KAI2 and D14 both act through the MAX2 (MORE AXILLARY BRANCHING2) F-box protein to target proteins of the SMAX1-LIKE (SUPPRESSOR OF MAX2 1) (SMXL) family for degradation, but the signalling events downstream of this step are unclear in both pathways2. Here, we show that kai2 phenotypes arise because of a failure to downregulate auxin transport from the seedling shoot apex towards the root system, rather than a failure to respond to light per se. We demonstrate that KAI2 controls the light-induced remodelling of the PIN-mediated auxin transport system in seedlings, promoting the reduction of PIN3, PIN4, and PIN7 abundance in older tissues, and the increase of PIN1, PIN2, PIN3, and PIN7 abundance in the root meristem, consistent with transition from elongation-mediated growth in the dark to meristematically-mediated growth in the light. We show that removing PIN3, PIN4 and PIN7 from kai2 mutants, or pharmacological inhibition of auxin transport and synthesis, is sufficient to suppress most kai2 seedling phenotypes. KAI2 is not required for the light-mediated changes in PIN gene expression but is required for the changes in PIN protein abundance at the plasma membrane; we thus propose that KAI2 acts to promote vesicle trafficking, consistent with previous suggestions about D14-mediated signalling in the shoot3.

plant biology↗

bioRxiv2020

Estimating intracranial pressure via low-dimensional models: toward a practical tool for clinical decision support at multi-hour timescales

AbstractBroad clinical application of non-invasive intracranial pressure (ICP) monitoring using computational models requires a method of modeling ICP on the basis of easily measured patient data such as radial or brachial arterial blood pressure (ABP). These models may be highly complex, rendering them too slow for clinical and operational use, or may rely on data that is not consistently available. Coupling these models to an upstream vasculature component model decreases data requirements. For the purposes of clinical decision support at multi-hour timescales, two natural choices for model development are to increase intracranial model complexity or to include feedback mechanisms between ICP and vascular model components. We compare the performance of these two approaches by evaluating model estimates against observed ICP in the case of a slow hypertensive event from a publically available dataset. The simpler model with bi-directional feedback requires minimal identifiability and is sufficiently accurate over these timescales, while a more complex is difficult and expensive to identify well enough to be accurate. Furthermore, the bi-directional simple model operates orders of magnitude faster than the more anatomically accurate model when driven by high-resolution ABP. It may also be configured to use lower resolution ABP summary data that is consistently clinically available. The simpler models are fast enough to support future developments such as patient-specific parametrization and assimilation of other clinical data streams which are illustrated during the case of a complex ICP regime for a different patient. We present model comparisons to highlight the advantages of the incorporated simple model and its possible predictive power with further optimization.Competing Interest StatementThe authors have declared no competing interest.View Full Text

bioengineering↗

bioRxiv2019

Auxin export from proximal fruits drives arrest in competent inflorescence meristems

A well-defined set of regulatory pathways control entry into the reproductive phase in flowering plants [1]. Conversely, little is known about the mechanisms that control the end of the reproductive phase ( floral arrest), despite this being a critical process for optimising fruit and seed production. Complete fruit removal or lack of fertile fruit-set in male sterile mutants, for example male sterile1 (ms1), prevents timely floral arrest in the model plant Arabidopsis [2]. These observations formed the basis for Hensel and colleagues model in which end-of-flowering was proposed to result from a cumulative fruit/seed-derived signal that caused simultaneous global proliferative arrest (GPA) in all inflorescences [2]. Recent studies have suggested that end-of-flowering involves gene expression changes at the floral meristem which are at least in part controlled by the FRUITFULL-APETELA2 pathway [3,4], however there is limited understanding of how this process is controlled and the communication needed at the whole plant level. Here, we provide new information providing a framework for the fruit-to-meristem (F-M) communication implied by the GPA model [5]. We show that floral arrest in Arabidopsis is not global and does not occur synchronously between branches, but rather that the arrest of each inflorescence is a local process, driven by auxin export from fruit proximal to the inflorescence meristem (IM). Furthermore, we show that inflorescence meristems are only competent for floral arrest once they reach a certain developmental age. Understanding the regulation of floral arrest is of major importance for the future manipulation of flowering to extend and maximise crop yields.

plant biology↗

bioRxiv2019

Root density sensing allows pro-active modulation of shoot growth to avoid future resource limitation

Plants use environmental cues to determine their optimal root and shoot growth. It is well known to gardeners and horticulturists alike that soil volume - most commonly in the form of pot size - strongly restricts plant growth, but the mechanisms by which this effect occurs remain unclear. Here, we show that shoot growth scales directly with soil volume, independently of the nutritional content of the soil, and that plants can become volume restricted even in the presence of abundant resources. We show that plants can detect their soil volume as early as 3 weeks post germination, and that shoot growth restriction therefore constitutes a pro-active decision by the plant to avoid resource limitation later in the life cycle. Shoot growth restriction is not directly linked to root growth restriction, and does not occur in response to the mechanical detection of the pot walls. Rather, we show that plants detect their soil volume by detecting the density of roots in the proximity of their root system. As such, volume restriction may be intimately connected with the mechanism by which plants sense and respond to the roots of other plants in the rhizosphere. Our work demonstrates the remarkable ability of plants to make pro-active decisions about their growth to ensure they can complete their cycle, and has important implications for agricultural practise regarding both nutrient use efficiency and yield.

plant biology↗

bioRxiv2019

KAI2 regulates root and root hair development by modulating auxin distribution

Strigolactones (SLs) are endogenous signalling molecules that play important roles in controlling plant development. SL perception is closely related to that of karrikins, smoke-derived compounds presumed to mimic endogenous signalling molecules (KLs). SLs have been suggested to regulate root development. However, perception of both molecules requires the F-box protein MAX2 and the use of max2 mutants has hampered defining the exact role of SLs in roots. Here we dissect the role of SL and KL signalling in Arabidopsis root development using mutants defective in the /{beta} hydrolase receptors D14 and KAI2, which specifically perceive SLs and KLs, respectively. Both pathways together regulate lateral root density (LRD), but contrary to previous reports, KL signalling alone controls root hair density, root hair length and additionally root skewing, straightness and diameter. Members of the SMXL protein family are downstream targets of SL (SMXL6, 7, 8) and KL (SMAX1, SMXL2) signalling. We identified distinct and overlapping roles of these proteins in the regulation of root development. Both SMAX1/SMXL2 and SMXL6/SMXL7/SMXL8 regulate LRD, confirming that SL and KL signalling act together to regulate this trait, while the KL-signalling specific SMAX1 and SMXL2 regulate all other investigated root traits. Finally, we show that KL signalling regulates root hair development by modulating auxin distribution within the root.

plant biology↗

bioRxiv2017

Reassessing the evolution of strigolactone synthesis and signalling

Strigolactones (SLs) are an important class of carotenoid-derived signalling molecule in plants, which function both as exogenous signals in the rhizosphere, and as endogenous plant hormones. In flowering plants, SLs are synthesized by a core pathway of four enzymes, and are perceived by the DWARF14 (D14) receptor, leading to degradation of SMAX1-LIKE7 (SMXL7) target proteins in a manner dependent on the SCFMAX2 ubiquitin ligase. The evolutionary history of SLs is poorly understood, and it is not clear whether SL synthesis and signalling are present in all land plant lineages, nor when these traits evolved. We have utilized recently-generated genomic and transcriptomic sequences from across the land plant clade to resolve the origin of each known component of SL synthesis and signalling. We show that all enzymes in the core SL synthesis pathway originated at or before the base of land plants, consistent with the previously observed distribution of SLs themselves in land plant lineages. We also show that the late-acting enzyme LATERAL BRANCHING OXIDOREDUCTASE (LBO) is considerably more ancient than previously thought. We perform a detailed phylogenetic analysis of SMXL proteins, and show that specific SL target proteins only arose in flowering plants. We also assess diversity and protein structure in the SMXL family, identifying several previously unknown clades. Overall, our results suggest that SL synthesis is much more ancient than canonical SL signalling, consistent with the idea that SLs first evolved as rhizosphere signals, and were only recruited much later as hormonal signals.

plant biology↗

bioRxiv2017

The complex origins of strigolactone signalling in land plants

Strigolactones (SLs) are a class of plant hormones that control many aspects of plant growth. The SL signalling mechanism is homologous to that of karrikins (KARs), smoke-derived compounds that stimulate seed germination. In angiosperms, the SL receptor is an /{beta} hydrolase known as DWARF14 (D14); its close homologue, KARRIKIN INSENSITIVE2 (KAI2), functions as a KAR receptor, and likely recognizes an uncharacterized, endogenous signal. Previous phylogenetic analyses have suggested that the KAI2 lineage is ancestral in land plants, and that canonical D14-type SL receptors only arose in seed plants; this is paradoxical, however, as non-vascular plants synthesize and respond to SLs. Here, we have used a combination of phylogenetic and structural approaches to re-assess the evolution of the D14/KAI2 family in land plants. We analyzed 339 members of the D14/KAI2 family from land plants and charophyte algae. Our phylogenetic analyses show that the divergence between the eu-KAI2 lineage and the DDK (D14/DLK2/KAI2) lineage that includes D14 occurred very early in land plant evolution. We identify characteristic structural features of D14 and KAI2 proteins, and use homology modelling to show that the earliest members of the DDK lineage structurally resemble KAI2, and not D14 proteins. Furthermore, we show that probable SL receptors in non-seed plants do not have D14-like structure. Our results suggest that SL perception has relatively relaxed structural requirements, and that the evolution from KAI2-like to D14-like protein structure in the DDK lineage may have been driven by interactions with protein partners, rather than being required for SL perception itself.

plant biology↗