Conference on Study of photosynthesis in photo-symbiotic cnidarians

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

Cell Metabolism Light-dependent reactions H+ Q OEC Pheo NADP H+ ATP H+ Fe-S PC 2H2O O2 Cyanobacteria Eukarya

Organelle ≠ Endosymbiont

Dorrell and Howe, 2012. Journal of Cell Science, 125(8).

A series of endosymbiont or plastid

acquisition events has lead to a huge

diversity of photosynthetic eukaryotes

Cnidarians

Kayal et al. 2018. BMC Evolutionary Biology, 18:68.

Symbiosis could have evolved several times and independently in cnidarians

Cnidarians

Kayal et al. 2018. BMC Evolutionary Biology, 18:68.

Symbiosis could have evolved several times and independently in cnidarians

It emits fluorescence as a mechanism

of de-excitation after radiative energy

has been absorbed.

Chlorophyll a is one of the main pigments

in oxygenic photosynthetic complexes.

Wavelenghts absorbed by chloropyhll a Chlorophyll a fluorescence H+ Q OEC Pheo NADP H+ ATP H+ Fe-S PC 2H₂O O2

Time

Fmax

Fo

-Reaction center

closed, not available for photosynthesis

Fv Fm Photosynthetic efficiency

=

=

In vivo Chl a fluorescence yield is related to photosynthetic capacity

Fluorescence

Reaction center

open, available for photosynthesis

Photo chemistry Fluor es cen ce (a. u .) Saturating flash Photo chemistry Strong and short

Saturating flash _Fluorescence

Detecting light

Photosynthetic efficiency under

light

*

=

Irradiance r Electron Transfer Rate

Imaging fluorescence camera (SpeedZen camera)

Actinic light source FR light filter

Mastigias papua

Fluorescence

True color picture

2.2

Cassiopea xamana

Oxygen detector system Oxygen and fluorescence

simultaneous acquisition H+ Q OEC Pheo NADP H+ ATP H+ Fe-S PC 2H2O O2 O₂ exchange rate Increasing light intensity Electron Transfer Rate Increasing light intensity

(Pictures from 2008)

The Jellyfish Lake in Eil Malk, Palau,

used to be inhabited by the golden

jellyfish Mastigias papua.

https://commons.wikimedia.org

Republic of Palau

(Pictures from 2008)

The Jellyfish Lake in Eil Malk, Palau,

used to be inhabited by the golden

jellyfish Mastigias papua.

https://commons.wikimedia.org

Republic of Palau

Uet era Ngermeuangel (NLK) Goby lake (GLK)

Ngerchaol cove (NCK)

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

Maximum quantum yield of PSII 28 30 32 34 36 38 -2 -1 0 1 2 3 4 5 Temp er atur e (° C) heat-stress control day

Temperature profile of control and heat stress experiment

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 -c -H -c -H -c -H NCK GLK NLK Fv /Fm 0 1 2 3 4 5 day

No signs of electron transfer rerouting could be observed.

-2 -1 0 1 2 0 100 200 300 MEDIUM NCK CTRL NCK HEAT _-2 -1 0 1 2 0 100 200 GLK CTRL GLK HEAT -2 -1 0 1 2 0 100 200 NLK CTRL NLK HEAT rETR O 2 ex ch an ge ra te (a.u. /m in)

The anemone is azooxanthellated

Other cnidarian species inhabit this lake,

like the anemone Entacmaea medusivora

https://www.flickr.com/photos/luxtonnerre/

https://coralreefpalau.org/research/marine-lakes/jellyfish-lake/ Fautin and Fitt, 1991. Hydrobiologia, 216–217:453–61.

?

Pictures by Eric Rottinger

What’s the fate of jellyfish’s algal symbionts

when they are eaten by anemones?

t=0h (JF in mouth) t=1h (JF in gut) t=3h t=4-5h

Feeding an anemone with a jellyfish

-Starved anemone -Mastigias -1h/3h of digestion -Mastigias (NLK) -Entacmaea (NLK) True color picture Chl a fluoresc

Uet era Ngermeuangel (Jellyfish lake)

Ongeim'l Tketau (Jellyfish lake)

Mastigias papua

Enctamaea medusivora

-Faeces from anemones

-Sediment of non fed anemones

https://coralreefpalau.org/research/marine-lakes/jellyfish-lake/

U p o n d i g e s t i o n o f p h o t o sy n t h e t i c j e l l y f i s h e s M . p a p u a b y t h e a n e m o n e E . m e d u s i v o r a , Sy m b i o d i n i a c e a e c e l l s a re n o t

d i g e s te d a n d s tay p h o t o sy n t h e t i c a l l y c o m p e te n t .

~1 cm

Keshavmurthy et al., 2013. Scientific Reports, 3:1520

Biophysical analyses

of bioenergetics on

coral slices

1 cm Coral slice

Aquarium

Stylophora pistillata (Milka variety) branch tips were cut to get small

slices for spectroscopic measurements

Chl a fluorescence

0.7

Fv/Fm

Colony growing in aquarium conditions

0 0.2 0.4 0.6 0.8 0 2 4 6 Fv/F m Thickness (mm) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Colony day 0 Fragments day 0 Fragments day 1 Fragments day 2 Fv/F m Day 0 1 2 1 cm Chla fluoresc Fv/Fm

Actinic Light 660 nm IR light Reference Detector Filter 705nm Sample

Measurement of PSI activity

Spectrophotometric measurements on coral slices

*

*

*

*

It is possible to analize a small fraction of coral when inhibitors are needed

Eyal et al., 2019 in Mesophotic Coral Ecosystems.

0.5 0.55 0.6 0.65 0.7 0.75

Shallow water Deep water

Fv

/Fm

Shallow water coral 3-5 meters depth

Deep water coral 30-40 meters depth

Corals collected at two different depths

-20 -15 -10 -5 0 R ( µm ol O 2 min -1 cm -2)

Electron cycling at PSI level is more active in Shallow water corals

Shallow water Deep water

CE F (s -1) H+ Q OEC Pheo NADP H+ ATP H+ Fe-S PC 2H2O O2

Ciclyc Electron Flow

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

Thanks to Grant sources and laboratory team

Pierre CARDOL, PhD FRS-FNRS Senior Research Associate Genetics and Physiology of Microalgae

Institute of Botany, B22

ERC Consolidator Grant – H2020 – BEAL – 2016-2021

Stephane ROBERTY, PhD

Laboratoire de Physiologie Animale et Écophysiologie, J-C. Plumier