Study of photosynthesis in photo-symbiotic cnidarians Félix Vega de Luna Doctorat de Biochimie, Biologie moléculaire et cellulaire, Bioinformatique et modélisation Genetics and Physiology of Microalgae – Institute of Botany, B22 InBioS – Phytosystems day Light-dependent reactions Metabolism Cell NADP ATP H+ Pheo Fe-S Cyanobacteria Q Eukarya O PC + 2H2O OEC 2 H H+ A series of endosymbiont or plastid acquisition events has lead to a huge diversity of photosynthetic eukaryotes Organelle ≠ Endosymbiont Dorrell and Howe, 2012. Journal of Cell Science, 125(8). Symbiosis could have evolved several times Cnidarians and independently in cnidarians Kayal et al. 2018. BMC Evolutionary Biology, 18:68. 1.3 Symbiosis could have evolved several times Cnidarians and independently in cnidarians Kayal et al. 2018. BMC Evolutionary Biology, 18:68. Symbiodiniaceae family Chlorophyll a is one of the main pigments in oxygenic photosynthetic complexes. NADP ATP H+ Pheo Fe-S Q O PC + 2H2O OEC 2 H H+ Chlorophyll a Wavelenghts absorbed fluorescence It emits fluorescence as a mechanism by chloropyhll a of de-excitation after radiative energy has been absorbed. In vivo Chl a fluorescence yield is related to photosynthetic capacity Strong and short Fluorescence Saturating flash Detecting light Fluorescence Photo Photo Reaction center chemistry chemistry open, available for photosynthesis Reaction center closed, not available for photosynthesis Available Fmax - .) capacity for Fv Fmax – Fo a.u Photosynthetic photochemistry ( efficiency = Saturating = Fm = Fmax activity Fluorescence Fo - Photosynthetic Irradiance r Electron Transfer Rate efficiency under * = Time light Saturating flash 2.2 Imaging fluorescence camera (SpeedZen camera) FR light filter Actinic light source Johnson et al. 2009. Photosynth Res 102. True color picture Fluorescence Mastigias papua Cassiopea xamana Entacmaea quadricolor Oxygen and fluorescence simultaneous acquisition Oxygen detector system NADP ATP H+ O Pheo Fe-S Electron 2 Q exchange Transfer O PC + rate 2H2O OEC 2 H Rate H+ Increasing light Increasing light intensity intensity (Pictures from 2008) The Jellyfish Lake in Eil Malk, Palau, used to be inhabited by the golden jellyfish Mastigias papua. Republic of Palau https://commons.wikimedia.org Sampling campaign in 2018 to Palau (Pictures from 2008) The Jellyfish Lake in Eil Malk, Palau, used to be inhabited by the golden jellyfish Mastigias papua. Republic of Palau https://commons.wikimedia.org Sampling campaign in 2018 to Palau Ngerchaol cove (NCK) Goby lake (GLK) Uet era Ngermeuangel (NLK) Jellyfishes collected with the help of Gerda Ucharm and Lori Colin (CRRF, Koror, Palau) from the Uet era Ngermeuangel lake (NLK), Goby lake (GLK), and from the Ngerchaol cove (NCK) in January 2018, Palau and analyzed at PICRC, Koror, Palau. The specimens were maintained in the Palau International Coral Reef Center Temperature profile of control and Maximum quantum yield of PSII heat stress experiment 0.7 38 0.6 0.5 C) ° 36 0.4 0.3 34 Fv/Fm 0.2 32 0.1 0.0 30 -c -H -c -H -c -H Temperature ( Temperature 28 NCK GLK NLK day -2 -1 0 1 2 3 4 5 day 0 1 2 3 4 5 heat-stress control 2 2 2 1 1 1 0 0 0 0 100 200 300 0 100 200 0 100 200 -1 -1 GLK CTRL -1 exchange rate (a.u./min) rate exchange MEDIUM NCK CTRL NLK CTRL 2 GLK HEAT O NLK HEAT -2 NCK HEAT -2 -2 rETR No signs of electron transfer rerouting could be observed. Other cnidarian species inhabit this lake, like the anemone Entacmaea medusivora https://www.flickr.com/photos/luxtonnerre/ The anemone is azooxanthellated Fautin and Fitt, 1991. Hydrobiologia, 216–217:453–61. https://coralreefpalau.org/research/marine-lakes/jellyfish-lake/ What’s the fate of jellyfish’s algal symbionts when they are eaten by anemones? ? Pictures by Eric Rottinger -5 minutes of digestion Feeding an anemone with a jellyfish -Mastigias -1h/3h of digestion Uet era Ngermeuangel (Jellyfish lake) -Starved anemone Mastigias papua Ongeim'lTketau (Jellyfish lake) Enctamaea medusivora -Mastigias (NLK) -Entacmaea (NLK) True color picture t=0h (JF in mouth) t=1h (JF in gut) t=3h t=4-5h ~12 h later Chl a -Faeces from anemones fluoresc -Sediment of non fed anemones Upon digestion of photosynthetic jellyfishes M. papua by the anemone E. medusivora, Symbiodiniaceae cells are not digested and stay photosynthetically competent. Vega de Luna et al., 2019. FEMS Microbiology Ecology, 95. https://coralreefpalau.org/research/marine-lakes/jellyfish-lake/ Biophysical analyses of bioenergetics on coral slices Stylophora pistillata (Scleractinia, Anthozoa) ~1 cm Keshavmurthy et al., 2013. Scientific Reports, 3:1520 Stylophora pistillata (Milka variety) branch tips were cut to get small slices for spectroscopic measurements Fragments followed by Chla fluorescence Coral slice Colony growing in aquarium conditions 0.7 1 cm Chla Day 1 cm fluoresc Fv/Fm 0.6 0 0.5 0.4 1 Fv/Fm 0.3 0.2 Aquarium 0.1 2 0 Colony day Fragments Fragments Fragments Chl a fluorescence 0 day 0 day 1 day 2 0.7 0.8 0.6 0.4 Fv/Fm 0.2 0 0 2 4 6 Fv/Fm Thickness (mm) Measurement of PSI activity Spectrophotometric measurements on coral slices IR light Actinic Light Reference 660 nm * Detector * Light Sample Filter * 705nm * Detector It is possible to analize a small fraction of coral when inhibitors are needed Eilat Eyal et al., 2019 in Mesophotic Coral Ecosystems. Corals collected at two different depths 0.75 0.7 0.65 Fv/Fm 0.6 0.55 0.5 Shallow water Deep water 0 1 - -5 2) - -10 cm Shallow water coral Deep water coral -15 R (µmol O2 min O2 (µmol R 3-5 meters depth 30-40 meters depth -20 Electron cycling at PSI level is more active in Shallow water corals 40 35 30 Ciclyc Electron Flow 25 1) - 20 NADP ATP CEF (s CEF H+ 15 Pheo Fe-S 10 Q + 5 O2 PC 2H2O OEC H H+ 0 Shallow water Deep water DCMU Main remarks • Coral slices survive (up to 48hr) and do not suffer a noticeable consequence in aquarium conditions. • Its optical properties allow spectroscopic measurement of photosynthetic processes. • We revealed a higher CEF capacity in shallow water corals compared with deep water ones. Take home message ● Typical and detailed photosynthetic in vivo analyses can be carried out in different photosymbiotic animals by sophisticated spectroscopic instrumentation Thanks to Grant sources and laboratory team Pierre CARDOL, PhD FRS-FNRS Senior Research Associate Stephane ROBERTY, PhD Genetics and Physiology of Microalgae Laboratoire de Physiologie Animale Institute of Botany, B22 et Écophysiologie, J-C. Plumier ERC Consolidator Grant – H2020 – BEAL – 2016-2021.