Biology subjects

Glover, B. J.

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

4 recordsLinked to original sources

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↗