Analysis of the different regulation levels and mechanisms of the nectar composition
Final Report Abstract
Floral nectar is produced by many angiosperm flowers to promote crossing mediated by pollinator visits. Sugars account for the largest share of the total nectar solutes, but it also contains a variety of amino acids, inorganic ions, and other compounds. The composition of individual nectars varies between species and these differences can have various reasons. On the one hand, the floral nectar composition may represent putative adaptations to the pollinator’s preferences and one the other hand systematic or phylogenetic relationships may have an impact. In addition, climatic factors or internal physiological processes, including the metabolism in the nectaries, may affect the composition in different plant species. To investigate the influence of different factors on nectar composition, the metabolite composition of nectar and nectaries (nectar-producing tissue) of several hundred plant species of the model family Bromeliaceae were analyzed. This is probably the most comprehensive study to date on this topic. It was shown that the pollinator type has a much higher influence on nectar composition than taxonomic affiliations or environmental factors. Apparently, the sugar composition is clearly influenced by the pollination type, whereas the amino acid and inorganic ion compositions are also influenced by the taxonomic group and several other factors, respectively. Of the environmental factors analysed, drought had the greatest effect on nectar composition. The changed composition in turn can have a negative impact on the plant-pollinator interactions. This is particularly important to note in light of increasing climate change. Nectar is produced in and secreted by nectaries. The composition of amino acids in nectaries and nectar is relatively similar. However, since their concentration in the nectaries is much higher than in the nectar, they must be selectively retained in the nectaries. Most of the amino acids in nectar probably originate from the phloem. However, synthesis of individual amino acids can also occur in the nectaries. Nectar production and secretion have so far been studied mainly in dicotyledonous species, especially Arabidopsis, while much less was known for monocotyledonous species. The biochemical and molecular processes in the nectaries were therefore analyzed in different bromeliad species, especially in Ananas comosus. The results obtained so far show that the molecular mechanisms of nectar production and secretion are not conserved in dicotyledonous and monocotyledonous plant species. For example, in contrast to many dicots, in A. comosus the sucrose concentration in the nectar was higher than in the nectaries and orthologs of SWEET9 seem to be generally absent in monocots. Therefore, the secretion of sucrose from the nectaries into the nectar via this pathway can be excluded. Instead, other mechanisms are probably involved in A. comosus, and evidence of active sugar export or exocytosis has been found.
Publications
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Nectar sugars and amino acids in day- and night-flowering Nicotiana species are more strongly shaped by pollinators’ preferences than organic acids and inorganic ions. PLOS ONE, 12(5), e0176865.
Tiedge, Kira & Lohaus, Gertrud
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Nectar Sugar Modulation and Cell Wall Invertases in the Nectaries of Day- and Night- Flowering Nicotiana. Frontiers in Plant Science, 9.
Tiedge, Kira & Lohaus, Gertrud
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Regulation der Nektarzusammensetzung bei Bromeliaceen. Dissertation, Universität Wuppertal
Göttlinger T.
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What Do Nectarivorous Bats Like? Nectar Composition in Bromeliaceae With Special Emphasis on Bat-Pollinated Species. Frontiers in Plant Science, 10.
Göttlinger, Thomas; Schwerdtfeger, Michael; Tiedge, Kira & Lohaus, Gertrud
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Influence of light, dark, temperature and drought on metabolite and ion composition in nectar and nectaries of an epiphytic bromeliad species (Aechmea fasciata). Plant Biology, 22(5), 781-793.
Göttlinger, T. & Lohaus, G.
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Comparative analyses of the metabolite and ion concentrations in nectar, nectaries, and leaves of 36 bromeliads with different photosynthesis and pollinator types. Frontiers in Plant Science, 13.
Göttlinger, Thomas & Lohaus, Gertrud
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Origin and Function of Amino Acids in Nectar and Nectaries of Pitcairnia Species with Particular Emphasis on Alanine and Glutamine. Plants, 13(1), 23.
Göttlinger, Thomas & Lohaus, Gertrud
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Metabolic and transcriptomic analyses of nectaries reveal differences in the mechanism of nectar production between monocots (Ananas comosus) and dicots (Nicotiana tabacum).
Göttlinger, Thomas; Pirritano, Marcello; Simon, Martin; Fuß, Janina & Lohaus, Gertrud
