Eukaryotic tree of life

Eukaryotic tree of life

Eukaryota nested in Archaea

Zaremba-Niedzwiedzka et al. (2017), Nature

Eukaryotic tree of life

LECA (last Eukarotic common ancestor) = Excavate

Eukaryotic tree of life

Primary and secondary endosymbioses

Primary and secondary endosymbioses

Primary and secondary endosymbioses

Stiller et al., 2014

Complex red endosymbioses

Petersen et al., 2014, Genom. Biol. Evol.

Eukaryotic tree of life

Haptophyta

Haptophyta

▪ predominantly marine flagellates

▪ two flagella without mastigonemata

▪ haptonema – 6-7 MT in a cross-section

▪ plastids with lamellae comprised of 3 thylakoids, no stigma, no girdle lamella

▪ production of inorganic cellulosic or calcareous scales (coccoliths).

Satellite image of a bloom in the English Channel off the coast of Cornwall, 24 July 1999.

▪ significantly affecting the global clima on the Earth (biogeochemical cycle of carbon and sulphur)

Haptophyta

de Vargas et al. 2007

Dimethylsulphide (DMS) –

formation of clauds in the

atmosphere.

White tide – extensive bloom of

a haptophyte Emiliania huxleyi

White tide + clouds –

increasing of albedo (i.e.

increasing of total light

reflection from the Earth surface

– cooling down the Earth

Haptophyta

coiled haptonemaHaptonema

Haptophyta

▪ thin organelle resembling the flagellum

▪ variable length

▪ 6-7 microtubules arran-ged in a circle or a cross, surrounded by the ER cisterna

Chrysochromulina. Bacterial particles stick on the haptonema. They are

transported to the aggregation center. The clump of bacteria is then

transported to the end of haptonema, and delivered to the posterior cell

end, where it is engulfed.

Haptophyta

Haptonema

▪ ingestion ofbacteria and smaller eukaryotes(phygotrophy)

cellulosic scales

(Chrysochromulina)

calcareous coccoliths

(Cyrtosphaera)

silica scales

(Hyalolithus)

Scales

Prymnesium

Haptophyta - polysaccharide scales (cellulose)

Chrysochromulina sp.Ch. vexillifera

Tiny cellulosic scales formed in many

Haptophyte species

Chrysochromulina – only cellulosic

scales

Pleurochrysis carterae

Haptophyta - scales

In Coccolithophorids, calcified scales (called coccoliths) are usually formed in

addition to underlying organic scales.

(a) two calcit layers surround the polysaccharide scale.

Hymenomonas lacuna

Biosynthesis in Golgi

aparatus, each scale in it

own cisterna

Haptophyta - polysaccharide scales (cellulose)

Calcareous coccoliths surrounds the cell in one or several layers

(coccosphaere)

Haptophyta - coccoliths

Holococcoliths

calcification occurs extra-

cellularly, individual crystals

have simple morphologies, no

distinction between the rim

and central area

Heterococcoliths

calcification occurs intra-

cellularly, complex

morphologies, a rim of radial

crytal units surrounding

thecentral area

Haptophyta - coccoliths

Syracosphaera

n2n

n2n

n2n

Alisphaera

Emiliania

▪ holococcoliths and heterococcoliths occur on alternate phases of the life-cycle of single species

▪ it reflects a haplodiplontic life-cycle, with holococcoliths consistently occurring in the haploid phase

Syracosphaera

Biosynthesis – (1) Golgi vescicles fuse to form one big vesicle attached to the nuclear

membrane, (2) thin organic lamella is formed inside the vesicle, reticular body

(microtubular net) is attached outside, (3) calcification, (4) disappearing of reticular

body, (5) complete coccolith is transferred to the cell surface and released outside

Haptophyta - coccoliths

Emiliania huxleyi – biosynthesis of the heterococcolith

Haptophyta - coccoliths

Scyphosphaera

Biosynthesis (E. huxleyi)

Haptophyta - coccoliths

Calcification: production of CO2 utilised during the photosynthesis

2HCO3− + Ca2+ → CaCO3 + CO2 + H2O

Higher intensity of photoynthesis =

higher intensity of calcification.

There is a very fast, effective

transport of calcium ionts over the

plasmatic membrane. In Emiliania

huxleyi, one coccolith is formed ca

1 hour.

Haptophyta - calcification

Haptophyta – value of coccoliths

▪ utilisation of CO2 for the photosynthesis

▪ defence against the predators (higher cell volume) and pathogens (bacteria, viruses)

▪ regulation of floating (production of heavy coccoliths)

▪ diffraction of sunlight into the cell center (photosynthesis in deap-sea species)

Chrysochromulina

Haptophyta – plastids

▪ 1 - 2 plastids with pyrenoids

▪ 4 plastid membranes

▪ chlorophyl a + c (yellow-brown colour)

Calyptrosphaera

sphaeroidea - pyrenoid

Haptophyta – plastids

Chrysochromulina polylepis ichtyotoxins

Haptophyta – production of toxins

White Cliffs of Dover

Haptophyta – fossil records

▪ first appear in the fossil of the Late Triassic, approximately 220 million years ago

▪ the higher abundance during the Late Cretaceous (95 mya)

▪ 80 % of all coccolithophorids went extinct during the Cretaceous-Tertiary (K-T) event at the end of the Cretaceous

Evardsen et

al. 2000

18S rDNA

Pavlovaphyceae

Phaeocystales

Prymnesiales

Isochrysidales

(coccoliths)

Haptophyta – evolution and phylogeny

Pry

mn

esio

phy

ceae

Haptophyta, Pavlovaphyceae

▪ without coccoliths or organic scales

▪ two unequal flagella covered by a tiny hairs

▪ short, non-contractile haptonema

nákres Pavlova

named according to the famous

russian ballerina

Exanthemachrysis noctivaga

Haptophyta, Pavlovaphyceae

▪ originally described by Tomáš Kalina from peat bogs in Krkonoše Mts.

Haptophyta, Prymnesiophyceae, Phaeocystales

▪ primitive evolutionary lineage among haptophytes

▪ Phaeocystis pouchetii – flagellates in large mucilaginous colonies

▪ major emitter of DMS

Phaeocystis bloom

▪ foam accumulated on beaches

Chrysochromulina

Prymnesium

Haptophyta, Prymnesiophyceae, Prymnesiales

▪ unicellular flagellates with two flagella of equal length

▪ haptonema variable in its length, often contractile

▪ predominantly marine species

▪ non-calcified scales

Pleurochrysis carterae

Haptophyta, Prymnesiophyceae, Isochrysidales

▪ calcareous coccoliths

▪ two smooth flagella

Pleurochrysis

▪ simple coccoliths

Hymenomonas roseola

▪ freshwater

▪ in metaphyton of clear, oligotrophic waters

Emiliania huxleyi

▪ most abundant coccolithophore found in the Earth’s oceans, forming extensive blooms (white tides)

▪ significant impact on global climate

Emiliania huxleyi

Emiliania huxleyi

http://ina.tmsoc.org/Nannotax3/index.ph

p?dir=Coccolithophores&top=34&base=

300

Algirosphaera robusta

Thorosphaera

flabellata

Pontosphaera

syracusana

Isochrysidales - coccoliths

Florisphaera profunda

Braarudosphaera

bigelowi

Rhabdosphaera

clavigera

Isochrysidales - coccolithsF. profunda

Freshwater Haptophyta

Schalchian-Tabrizi et al. 2011

Cryptophyta▪ predominantly flagellates, flagella of unequal length

▪ coccoids (Tetragoniella), capsal, trichal (Bjornbergiella, soil in Havaii)

1 Cryptomonas curvata, 2 Rhodomonas pusilla, 3 Chroomonas

nordstedtii, 4 Chilomonas paramaecium

Cryptophyta – plastids

▪ 1-2 plastids (4 membranes)

▪ chlorophyls a+c2

▪ phycobiliproteins: (crypto)-

phycocyanin, (crypto)-

phycoerytrin in thylakoid

lumen

▪ starch (α-1-4-glucan) in

periplastidial space (between

ER and plastid membranes),

lipid granule, chrysolaminaran is

not produced!

▪ pyrenoid, stigma

▪ no girdle lamella

Rhodomonas

▪ plastids with lamellae comprised of 3 thylakoids

Cryptophyta – plastids

Cryptophyta - flagella

organic scale on the

flagellar surface

Cryptophyta – cell morphology

Cryptophyta - ejectosomes

▪ explosive structures surrounding the furrow, and under theplasmatic membrane

▪ two connected ribbons of different sizes, that are rolled up and under tension

▪ discharged upon mechanical or chemical stress irritating the cells

Cryptophyta – nucleomorph

▪ often attached to pyrenoids

▪ two membranes

Chroomonas coeruela – wavy periplast, inner and outer plates

Cryptophyta - periplast

Cryptomonas ovata – periplast beneath the plasmatic membrane

PM

▪ protein plates

Cryptomonas sp. – arrangement of plates

Cryptophyta - periplast

angular arrangement

of plates

plates

E = trichocysts (ejectosomes)EP = ejectosome

openings

hexagonal arrangement

of plates

Cryptophyta - periplast

Cryptophyta - reproduction

▪ asexual – schizotomy of flagellates

▪ sexual – isogamy, formation of planozygote (4 flagella)

Cryptophyta - ecology

▪ autotrophs, heterotrophs

▪ freshwater, marine, brackish

▪ endosymbionts in dinoflagellates, in a ciliate Mesodinium rubrum (red tides)

Amphidinium Mesodinium

Cryptophyta - systematics

▪ ca 20 genera, half of them in freshwater

▪ molecular data still unknown for many genera = traditional

systematics

▪ Cryptomonadales – free-living flagellates, genera delimited

by the colour of plastids

▪ olive-brown: Cryptomonas, Campylomonas

▪ blue-green: Chroomonas

▪ red-green: Rhodomonas

▪ colourless (loss of plastids): Chilomonas

CryptomonasCryptomonas reflexa Cryptomonas rostratiformis

Cryptomonas sp.

Cryptomonas acuta

Cryptomonas, CampylomonasCampylomonas

Cryptomonas, Campylomonas

▪ Hoef-Emden (2003): cell dimorphism during the

haplo/diplontic cell cycle

Chroomonas coeruela

Chroomonas

nordstedtii

Chroomonas diplococca

Chroomonas

RhodomonasRhodomonas baltica

Rhodomonas duplex

Rhodomonas cf. marina (Balt)

Chilomonas – heterotrophic

Chilomonas paramecium

Hemiselmis – marine

Cryptophyta - molecular data

▪ phylogenetic data do not correspond with the traditional

morfological features - needed revision of the genus

Cryptomonas

Hoef-Emden et al., 2002

Proteomonas

Chroomonas

Rhodomonas

Cryptomonas

Chilomonas

Cryptophyta - molecular data▪ phylogenetic data do correspond with pigment composition

C. paramecium

Cryptophyta - molecular data

▪ 3 independent losses of plastids (photosynthesis)

▪ increased mutation rate in colourless lineages (change of

life style)