Metabolomic Profiling of Nicotiana Spp. Nectars Indicate That Pollinator Feeding Preference Is a Stronger Determinant Than Plant Phylogenetics in Shaping Nectar Diversity.

Fredy A Silva,Xingche Guo,Elizabeth C Chatt,Daniel S Nettleton,Adel Guirgis,Siti-Nabilla Mahalim,Basil J Nikolau,Robert W Thornburg

doi:10.3390/metabo10050214

Fredy A Silva, Xingche Guo + Show 6 more

Open Access

https://doi.org/10.3390/metabo10050214

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Journal: Metabolites	Publication Date: May 22, 2020
Citations: 9	License type: CC BY 4.0

Affiliation: Iowa State University, University of Sadat City

Abstract

Floral nectar is a rich secretion produced by the nectary gland and is offered as reward to attract pollinators leading to improved seed set. Nectars are composed of a complex mixture of sugars, amino acids, proteins, vitamins, lipids, organic and inorganic acids. This composition is influenced by several factors, including floral morphology, mechanism of nectar secretion, time of flowering, and visitation by pollinators. The objective of this study was to determine the contributions of flowering time, plant phylogeny, and pollinator selection on nectar composition in Nicotiana. The main classes of nectar metabolites (sugars and amino acids) were quantified using gas chromatography/mass spectrometric analytical platforms to identify differences among fifteen Nicotiana species representing day- and night-flowering plants from ten sections of the genus that are visited by five different primary pollinators. The nectar metabolomes of different Nicotiana species can predict the feeding preferences of the target pollinator(s) of each species, and the nectar sugars (i.e., glucose, fructose, and sucrose) are a distinguishing feature of Nicotiana species phylogeny. Moreover, comparative statistical analysis indicate that pollinators are a stronger determinant of nectar composition than plant phylogeny.

Highlights

Nectars are metabolite-rich biological fluids that function as the primary floral reward offered to animal mutualists to sustain plant–pollinator relationships [1]
The sugars and amino acids, which are the major classes of nectar metabolites, are thought to be especially influential in pollinator attraction [3,13,14]
Honey bees and short tongue pollinators prefer concentrated hexose-rich nectars, whereas hummingbirds prefer sucrose-rich nectars [7,16,17]

Summary

Introduction

Nectars are metabolite-rich biological fluids that function as the primary floral reward offered to animal mutualists to sustain plant–pollinator relationships [1]. These fluids are produced and secreted from nectary glands. The nectar composition, in addition to other floral traits, such as morphology, color, and scent, recruits pollinators to promote plant reproductive success through improved pollination and seed set [2,3,4,5,6]. Sugar concentrations and compositional ratios are major determinants of nectar viscosity [15], which facilitates efficient feeding by pollinators such as honeybees, short tongue pollinators or hummingbirds [7,16,17]. Amino acids modulate the neuronal response of the pollinators and act as phagostimulatory metabolites (i.e., γ-aminobutyric acid (GABA), proline, ornithine and β-alanine) [9,22,23]

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