Chromista Thomas Cavalier-Smith (1981)

substantial modification of existing system of 5 kingdoms

Chromista

common ancestor – origin by a secondary endosymbiosis of Rhodophyte plastids

main autotrophic lineages: Cryptophyta, Haptophyta, Stramenopiles

analýza plastidových genů

Chromista chloroplasts – 4 membranes (2 of plastid origin + 2

derived from ER), girdle lamella

chlorophyl a, c; diato/diadinoxanthophyl cycle

storage product - chrysolaminaran (β-1,3-1,6-glucan)

pleuronematic flagella

interplastidial stigma in flagellates

Chromista

common ancestor – origin by a secondary endosymbiosis of Rhodophyte plastids

secondary loss of plastids in several groups of organisms

Chromista

common ancestor – origin by a secondary endosymbiosis of Rhodophyte plastids

secondary loss of plastids in several groups of organisms

67 Taxa

159 protein

genes

Brown et al. 2012

150 Taxa

250 protein genes

Burki et al. 2016

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 haptonema Haptonema

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 of bacteria 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

n 2n

n 2n

n 2n

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

mnes

iop

hy

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 - coccoliths F. 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 the plasmatic 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

Cryptomonas Cryptomonas reflexa Cryptomonas rostratiformis

Cryptomonas sp.

Cryptomonas acuta

Cryptomonas, Campylomonas Campylomonas

Cryptomonas, Campylomonas

Hoef-Emden (2003): cell dimorphism during the

haplo/diplontic cell cycle

Chroomonas coeruela

Chroomonas

nordstedtii

Chroomonas diplococca

Chroomonas

Rhodomonas Rhodomonas 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)