Floral nectar is a sugary solution produced by plants to entice pollinator visitation. A general mechanism for nectar secretion has been established from genetic studies in Arabidopsis (Arabidopsis thaliana); however, supporting metabolic and biochemical evidence for this model is scarce in other plant species. We used squash (Cucurbita pepo) to test whether the genetic model of nectar secretion in Arabidopsis is supported at the metabolic level in other species. As such, we analyzed the expression and activity of key enzymes involved in carbohydrate metabolism in squash nectaries throughout floral maturation and the associated starch and soluble sugars, as well as nectar volume and sugar under different growth conditions. Here we show that the steps that are important for nectar secretion in Arabidopsis, including nectary starch degradation, Suc synthesis, and Suc export, are supported by metabolic and biochemical data in C. pepo. Additionally, our findings suggest that sugars imported from the phloem during nectar secretion, without prior storage as starch, are important for generating C. pepo nectar. Finally, we predict that trehalose and trehalose 6-P play important regulatory roles in nectary starch degradation and nectar secretion. These data improve our understanding of how nectar is produced in an agronomically relevant species with the potential for use as a model to help us gain insight into the biochemistry and metabolism of nectar secretion in flowering plants.
Bibliographical noteFunding Information:
1This work was supported by the U.S. National Science Foundation (grant 1339246 to C.J.C.). 2Author for contact: firstname.lastname@example.org. 3Senior author. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Clay J. Carter (email@example.com). E.M.S. and C.J.C. designed the experiments and wrote the article together; E.M.S. performed the majority of the experiments and analyzed the data, with assistance from E.J. [OPEN]Articles can be viewed without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.19.00470
This work was supported by the U.S. National Science Foundation (grant 1339246 to C.J.C.).
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