OOS 19-2
A coordinated pathway for the synthesis and secretion of antimicrobial nectar
It is estimated that nearly 90% of all of all flowering plant species are dependent on animals for reproduction, with nectar being the primary reward offered to pollinators for visitation. Despite its central role in plant-pollinator interactions, the mechanisms by which nectar is synthesized and secreted, as well as how plants limit microbial growth within nectar, are poorly understood. To answer these unaddressed questions, we used reverse genetics and biochemical approaches to identify conserved pathways for the production of antimicrobial nectar in the eudicots.
Results/Conclusions
We have identified a coordinated pathway for nectar production within floral nectaries involving (i) sucrose biosynthesis, (ii) sucrose export by a sugar transporter (SWEET9), and (iii) post-secretory hydrolysis of sucrose by extracellular invertases, which thereby creates the mix of sugars observed in nectars. Perturbation of any one of the steps in this pathway abolished nectar production in species from multiple clades of the eudicots. The recruitment of this pathway may have been a key innovation that coincided with the evolution of core eudicots that produce nectar to reward pollinators. Conversely, nectars from different eudicot species contain vast arrays of different proteins, which appear to be primarily involved in limiting microbial growth. A comparative overview of the roles of these antimicrobial proteins from different species will be presented.