Ido Izhaki - Current research project

The role of secondary metabolites in floral nectar in mediating the interactions between plants and microorganisms

(with Dr. Malka Halpern, Prof. Gidi Ne'eman and Dr. Yoram Gerchman)

Project description:

Traditionally, pollination and herbivory have been treated as separate ecological events in
which plants and animals interact. Until recently secondary compounds, many of which are feeding deterrents, were mostly considered to play a major role in the coevolution of plants and their herbivores. However, the fact that many plant species contain secondary compounds in their nectar raises the question of what role these substances play in the mutual interactions with their pollinators. Nectar is a reward produced to attract pollinators. However, traits that attract pollinators may also attract other organisms, such as microbes and nectar robbers, which are likely to decrease plant fitness. Plants thus face an evolutionary dilemma: how to make their nectar attractive to legitimate pollinators but unattractive to detrimental consumers.
    Secondary compounds in nectar might offer a novel solution to this evolutionary dilemma, mediating interactions between plants and the disparate array of nectarivores. Several “adaptive hypotheses” have been proposed to explain the potential functions of secondary compounds in floral nectar, suggesting to view them as conferring fitness benefits to the plant. To date, most of these hypotheses have been overlooked and not experimentally tested.
    In the research project we aim to investigate the role of plant secondary metabolites in mediating the complex association between microorganisms and plants’ floral nectar. To that end, we plan to test several predictions on nectar’s secondary metabolites and microorganisms relationships. No studies have rigorously quantified the effect of nectar secondary metabolites on nectar microorganisms and subsequent plant-microb-pollinator interactions on plant fitness.
    To examine these predictions we will study and compare nectar and leaves microflora community and nectar chemical profile (primary and secondary metabolites) of six plant species so as to identify nectar and species specific microflora and secondary metabolites. We also propose to test the effect of nectar microflora on the nectar chemical composition. Finally we plan to evaluate the effect of the nectar microflora on foraging behavior of nectar
consumers and plant fitness parameters. Our methodology will include modern and sophisticated techniques such as DGGE, GC-MS, HPLC (-MS), Amino Acid Analyzer and axenic and transgenic plants techniques.
    We expect the use of such tools, together with the multidisciplinary approach adopted, to yield significant new insight into the role of secondary compounds in a complex microorganism-pollination system.

Examples of plants which contain secondary metabolites in their nectar:

hy       hy  

Hyoscyamus arueus            Hyoscyamine
               (SOLANACEAE )  

ni               ni

    Nicotiana alata                 Nicotine                       (SOLANACEAE )

ci              ca

     Citrus grandis                 Caffeine                                  (RUTACEAE)

am          am

Amygdalus communis          Amygdalin




Micrococcus luteus growth inhibition (top agar) by nectar of Aloe arborescens

This project is supported by the Israel Science Foundation (ISF) $200,000 (2008-2012)