Biology subjects

Glover, B. J.

Publications and source records attributed to Glover, B. J..

8 recordsLinked to original sources

bioRxiv2025

Replicated repurposing of an ancestral transcriptional complex in land plants

Transcriptional complexes with a common composition regulate the production of flavonoid pigments, trichomes, root hairs and other epidermal traits in seed plants. These complexes are composed of transcription factors from the MYB and basic helix-loop-helix (bHLH) families along with a tryptophan-aspartate repeat (WDR) scaffold protein (MBW complexes). The MYB member has been found to be the most pathway-specific component of the complex and modifications to these MYB genes are overrepresented in studies investigating the genetic basis of changes in pigmentation phenotypes across flowering plants. Here we investigated the orthologues of the MBW complex in a divergent lineage to understand its origin and evolution. We found evidence that these transcriptional complexes also form in the liverwort Marchantia polymorpha, indicating, together with an analysis of published gene family phylogenies, that they are ancestral to land plants. The functions of each of the two orthologous MYB genes, MpMYB14 and MpMYB02, both depend on the single orthologous bHLH gene, MpbHLH12. We could not assess the functional role of the WDR genes in M. polymorpha, due to low mutant recovery suspected to be caused by pleiotropic effects on viability. We propose that the two transcriptional complexes with alternative MYB paralogues in M. polymorpha represent an ancestral function, regulation of the flavonoid pathway, and a derived function, maturation of liverwort-specific oil bodies. Our findings imply a replicated pattern by which new complexes have evolved in independent land plant lineages, through duplication of the evolutionarily labile MYB member and co-option of its interaction partners.

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

HtDCR-like1 regulates the development of structurally coloured cuticle by modulating cuticle chemistry and mechanical properties in Hibiscus trionum

O_LIStructural colours are a unique trait present in some animals, plants and even bacteria. In Hibiscus trionum flowers, they arise from nano-scaled cuticular ridges and may improve pollinator foraging efficiency. These ridges result from the buckling of the cuticle which is thought to be controlled by multiple parameters including anisotropic cell growth, chemical differentiation of the cuticle and formation of two layers of different mechanical properties. C_LIO_LIHere we investigate further the molecular and physical mechanisms by which structural colours are achieved in Hibiscus trionum. We produced two transgenic lines overexpressing HtDCR-like1, encoding a BAHD acyltransferase involved in cuticle synthesis. Transgenic lines showed impairment of the production of cuticle striations. Cuticle thickness, cuticle chemistry, cell elongation and cuticle stiffness were then investigated to identify the cause of failed buckling. C_LIO_LIWe found that HtDCR-like1 overexpression leads to modification of cuticle chemistry, including a decrease in detectable C16H32O4 (10,16-DHP) and a change to the measured Youngs moduli of the cuticle layers without alteration of the cell growth pattern. C_LIO_LIThis work demonstrates the mechanisms by which gene regulation may control complex physical phenomena such as cuticle buckling via alteration of material properties of living tissues. C_LI

plant biology↗

bioRxiv2024

Characterisation of cuticle mechanical properties: analysing stiffness in layered living systems to understand surface buckling patterns

Development of a living organism is a highly regulated process during which biological materials undergo constant change. De novo material synthesis and changes in mechanical properties of materials are key for organ development; however, few studies have attempted to produce quantitative measurements of the mechanical properties of biological materials during growth. Such quantitative analysis is particularly challenging where the material is layered, as is the case for the plant cuticle on top of the plant epidermal cell wall. Here, we focus on Hibiscus trionum flower petals, where buckling of the cuticle forms ridges, producing an iridescent effect. This ridge formation is hypothesised to be due to mechanical instability, which directly depends upon the mechanical properties of the individual layers within the epidermal cells. We present measurements of the mechanical properties of the surface layers of petal epidermal cells through atomic force microscopy (AFM) and the uniaxial tensile tester for ultrathin films (TUTTUT), across growth stages. We found that the wavelength of the surface ridges was set at the ridge formation stage, and this wavelength was preserved during further petal development, most likely because of the plasticity of the material. Our findings suggest that temporal changes in biological material properties are key to understanding the development of biological surface patterns.

plant biology↗

bioRxiv2023

Complex petal spot formation in the Beetle Daisy (Gorteria diffusa) relies on spot-specific accumulation of malonylated anthocyanin regulated by paralogous GdMYBSG6 transcription factors

Gorteria diffusa has elaborate petal spots that attract male bee-fly pollinators through sexual deception but the genetic basis of G. diffusa petal spot development is currently unknown. Here we investigate the regulation of pigmentation during spot formation. We used UHPLC-MS/MS to determine the anthocyanin composition of spots and background pigmentation in G. diffusa. Combining gene expression analysis with protein interaction assays we characterised three R2R3-MYB genes regulating anthocyanin production in G. diffusa spots. We found that cyanidin 3-glucoside pigments G. diffusa ray floret petals. Unlike other petal regions, spots contain a high proportion of malonylated anthocyanin. We identified three paralogous subgroup 6 R2R3-MYB transcription factors that activate the production of petal spot pigmentation. The corresponding genes are upregulated in developing spots and induce ectopic anthocyanin production upon heterologous expression in tobacco. EMSAs and dual luciferase assays suggest that these transcription factors regulate genes encoding three anthocyanin synthesis enzymes: anthocyanidin synthase (GdANS), dihydroflavonol reductase (GdDFR) and malonyl transferase (GdMAT1), accounting for the spot-specific production of malonylated pigments. Here we provide the first molecular characterisation of G. diffusa spot development, showing that the elaboration of complex spots begins with accumulation of malonylated pigments at the base of ray floret petals, positively regulated by three subgroup 6 R2R3-MYB transcription factors.

plant biology↗

bioRxiv2022

The phylogenetic history of the Gorteria diffusa radiation sheds light on the origins of plant sexual deception

The morphologically diverse daisy species Gorteria diffusa employs varying levels of sexually deceptive pollination. The species comprises at least fifteen spatially and phenotypically discrete floral morphotypes that are associated with a range of pollination strategies, from generalism to highly specialised sexual deception involving visual mimicry of females of the bee-fly Megapalpus capensis. However, the pattern of evolution of the unique floral traits in this lineage remains unknown because the phylogenetic history of the closely related floral morphotypes has proved unresolvable using traditional approaches. Here we apply genotyping-by-sequencing (GBS), a reduced representation sequencing technology that has significantly increased the tractability of phylogenetic problems involving recent radiations, to the recalcitrant phylogenetic problem of Gorteria across its South African distribution. Population genomic analyses show that individuals group according to morphotype, irrespective of geographic proximity, highlighting the distinctiveness of the morphotypes at the genetic level. We resolve the phylogenetic history of the closely related morphotypes, demonstrating that they are mostly well supported monophyletic entities that are grouped into at least three distinct geographically separated clades. Our results suggest that both incomplete lineage sorting and introgression across geographical clades have previously hindered reconstruction of the phylogeny of this species complex that has diversified rapidly during the Quaternary. Sexual deception is a phylogenetically derived pollination strategy within the complex that evolved at least twice, and was likely achieved by sequential evolution of a set of floral traits that in combination elicit sexual responses from the bee-fly pollinator. While insight into the evolution of sexual deception has been limited by strong phylogenetic conservatism of this strategy in other plant lineages, our results both provide the framework, and confirm the utility of G. diffusa, for further understanding the genetic pathways and selective pressures underlying the complex phenotypes required to exploit insect mating behaviour for pollination.

evolutionary biology↗

bioRxiv2022

Morphoelastic modeling of pattern development in the petal epidermal cell cuticle

We use the model system Hibiscus trionum as a vehicle to study the origin and propagation of surface nano-ridges in plant petal epidermal cells by tracking the development of the cell shape and the cuticle. In this system, the cuticle develops two distinct subdomains, (i) an uppermost layer which increases in thickness and in-plane extension and (ii) a substrate. We quantify the pattern formation and geometrical changes and then postulate a mechanical model assuming that the cuticle behaves as a growing bi-layer. The model is a quasi-static morpho-elastic system and it is numerically investigated in two and three dimensional settings, using different laws of film and substrate expansion and boundary conditions. We recreate several features of the observed developmental trajectories in petals. We establish the respective roles of the layers stiffness mismatch, the underlying cell-wall curvature, the cell in-plane expansion and the thickness growth rates of the layers in determining the observed pattern features, such as the variance observed in amplitude and wavelength. Our observations provide evidence which justify the growing bi-layer description, and provide valuable insights into why some systems develop surface patterns and others do not.

plant biology↗

bioRxiv2022

Analysis of flavonol regulator evolution in the Brassicaceae reveals MYB12, MYB111 and MYB21 duplications associated with MYB11 and MYB24 gene loss

BackgroundFlavonols are the largest subgroup of flavonoids, possessing multiple functions in plants including protection against ultraviolet radiation, antimicrobial activities, and flower pigmentation together with anthocyanins. They are of agronomical and economical importance because the major off-taste component in rapeseed protein isolates is a flavonol derivative, which limits rapeseed protein use for human consumption. Flavonol production in Arabidopsis thaliana is mainly regulated by the subgroup 7 (SG7) R2R3-MYB transcription factors MYB11, MYB12, and MYB111. Recently, the SG19 MYBs MYB21, MYB24, and MYB57 were shown to regulate flavonol accumulation in pollen and stamens. The members of each subgroup are closely related, showing gene redundancy and tissue-specific expression in A. thaliana. However, the evolution of these flavonol regulators inside the Brassicaceae, especially inside the Brassiceae, which include the rapeseed crop species, is not fully understood. ResultsWe studied the SG7 and SG19 MYBs in 44 species, including 31 species of the Brassicaceae, by phylogenetic analyses followed by synteny and gene expression analyses. Thereby we identified a deep MYB12 and MYB111 duplication inside the Brassicaceae, which likely occurred before the divergence of Brassiceae and Thelypodieae. These duplications of SG7 members were followed by the loss of MYB11 after the divergence of Eruca vesicaria from the remaining Brassiceae species. Similarly, MYB21 experienced duplication before the emergence of the Brassiceae family, where the gene loss of MYB24 is also proposed to have happened. Due to the overlapping spatio-temporal expression patterns of the SG7 and SG19 MYB members in B. napus, the loss of MYB11 and MYB24 is likely to be compensated by the remaining homologs. ConclusionsWe identified a duplication of MYB12, MYB111, and MYB21 inside the Brassicaceae which is associated with MYB11 and MYB24 gene loss inside the tribe Brassiceae. We propose that gene redundancy and meso-polyploidization events have shaped the evolution of the flavonol regulators in the Brassicaceae, especially in the Brassiceae.

evolutionary biology↗