Colour development and pigment characterisation in flowers of Papaver nudicaule and Papaver rhoeas

The present thesis extended the knowledge about floral pigments and volatiles and their role in plant-pollinator interaction in two widely distributed Papaver species. The bright red flowers of P. rhoeas, the corn poppy, are characterised by a highly variable colouration in the UV-A wavelength range depending on geographical distribution. This colour polymorphism was found to be caused by different flavonol contents. While Eastern Mediterranean flowers with negligible UV reflectance produced flavonol glycosides, Central European flowers with substantial UV reflectance lacked these pigments almost completely. The flavonol structures consisted of kaempferol and quercetin aglycones with 3-O-glycosylation. Flavonoid biosynthesis is probably regulated in response to external conditions, e.g. UV irradiation, which might have contributed to the successful spread of P. rhoeas throughout the world. In P. nudicaule, pigments from three compound classes, the flavonoids, nudicaulins, and carotenoids, were identified in different flower sections and developmental stages of one yellow, orange, white, and red cultivar. Additionally, the floral scent differed between cultivars, with indole emitted in high amounts only by the yellow flowers. Western honeybees, the main pollinators, were able to distinguish cultivars based on colour and/or scent. For the unique yellow, flavoalkaloidal nudicaulin pigments, both enzymatic steps as well as the final, spontaneous step of the biosynthesis were unravelled by a combined transcriptomics, proteomics, metabolomics, and chemistry approach. The provision of free indole by an indole-3-glycerol-phosphate lyase-like enzyme in the petals and the establishment of certain reaction conditions are of high importance for the biosynthetic process. The results enabled the synthesis of the first non-glycosylated nudicaulin derivatives, which showed antiproliferative and cell toxic properties and thus potential for pharmaceutical applications.


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