Biology subjects

Fattorini, R.

Publications and source records attributed to Fattorini, R..

3 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↗

bioRxiv2023

AGAMOUS mediates timing of guard cell formation during gynoecium development

In Arabidopsis thaliana, stomata are composed of two guard cells that control the aperture of a central pore to facilitate gas exchange between the plant and its environment, which is particularly important during photosynthesis. Although leaves are the primary photosynthetic organs of higher plants, floral organs are also photosynthetically active. In the Brassicaceae, evidence suggests that silique photosynthesis is important for optimal seed oil content. A group of transcription factors containing MADS DNA binding domains is necessary and sufficient to confer floral organ identity. Elegant models, such as the ABCE model of flower development and the floral quartet model, have been instrumental in describing the molecular mechanisms by which these floral organ identity proteins govern flower development. However, we lack a complete understanding of how the floral organ identity genes interact with the underlying leaf development program. Here, we show that the MADS domain transcription factor AGAMOUS (AG) represses stomatal development on the gynoecial valves, so that maturation of stomatal complexes coincides with fertilization. We present evidence that this regulation by AG is mediated by direct transcriptional repression of the master regulator of the stomatal lineage, MUTE, and that this interaction is conserved among the Brassicaceae. This work extends on our understanding of the mechanisms underlying floral organ formation and provides a framework to decipher the mechanisms that control floral organ photosynthesis.

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↗