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Resurrection of Developmental Pathways in the Evolution of the Petal

Final Report Summary - PETALEVODEVO (Resurrection of Developmental Pathways in the Evolution of the Petal)

Angiosperms or flowering plants are the most diverse and widespread of land plants. Dominating most of the world’s habitats, they represent all of the major human crop plants. Flowers are the reproductive structures of angiosperms and facilitate numerous ecological and evolutionary interactions. A near constant feature in flowers, petals are crucial in attracting and interacting with pollinators; an estimated 35% of global crop production depends on petal-mediated animal pollination. Understanding how petals have evolved and how they contribute to the evolutionary success of angiosperms is a major goal in plant biology, while genetic manipulation of petals has been shown to influence agricultural success and crop yield. Our project concerned the evolution of petals in a group of flowering plants, the Caryophyllales, that contain numerous charismatic plants, like Cacti and ‘Living Stones’. We previously determined that following a loss of petals in the Caryophyllales, petals have subsequently re-evolved 9 times. Our goal was to develop the system to better understand the genetic pathways underlying the multiple origins of petals. Many of the novel petals that have evolved in the Caryophyllales develop from sterilised male organs – the stamens. We were consequently interested in the relationship between the origin of these petals and the stamens that give rise to them. We sought to describe the numerous separate instances in which stamens are transformed into petals, to better understand the forces that influence this transition. Conical cells on the surface of petals significantly enhance the attractiveness of a flower to its pollinators in a number of ways. They enhance colour saturation, provide tactile cues, reduce petal reflexing and increase petal temperature. We sought to understand how these conical cells appear on novel petals in the Caryophyllales, by understanding the evolutionary history of the subgroup 9 R2R3 MYB genes responsible for specifying these conical cells. Finally we investigated the complex evolution of a novel form of pigmentation in the Caryophyllales – the betalains – and explore their possible role colouring petals and attracting pollinators.