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Seminar Details

Exploring the enigmatic role of DMS during phytoplankton-microzooplankton interactions

Date

15/06/2017

Lecturers

Adva Shemi - Dept. of Plant and Environmental Sciences, Weizmann Institute of Science

Abstract

Background: Eukaryotic phytoplankton (haptophytes, dinoflagellates, but not diatoms) possess DMSP-lyase enzymes, which convert dimethylsulfoniopropionate (DMSP) to the volatile dimethylsulfide (DMS). This is a key reaction in marine food webs, as predators (copepods, birds and others) locate their prey by the DMS signal. Yet there is a debate whether DMSP-lyase activity attracts or deters microzooplankton grazers, which remove ~ 60% of the photosynthetic biomass daily. Research description: We isolated the DMSP-lyase Alma1 from the haptophyte Emiliania huxleyi and overexpressed an Alma-GFP fusion protein in the diatom Thalassiosira pseudonana (Tp-AG). This is the first DMS-producing diatom, now allowing to discern in vivo the unknown role of Alma1. We conducted grazing assays with the protist Oxyrrhis marina, which consumed significantly more Tp-AG than wild-type cells. To examine if this response has a broader ecological relevance, we are now developing methods to measure grazing by natural micrograzers from the Red Sea on Tp-AG cells. We also apply a novel chemical inhibitor for Alma1 named Br-DMSP. Preliminary results revealed that Br-DMSP reduced grazing efficiency by O. marina on Tp-AG and E. huxleyi cells. Conclusions and future perspectives: We suggest that DMS enhances herbivory by O. marina, and plan to test this finding with natural micrograzers as well. Our study raises fundamental questions regarding the physiologic role of Alma1 in algae and the possible evolutionary tradeoff between herbivory and stress acclimation. Future work will elucidate the role of DMS/P in the chemical communication between phytoplankton and microzooplankton.

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