what are these? · trimorphic: – three kinds of ... gonozooids • dactylozooids, these are...
TRANSCRIPT
Bioluminescence in Fireflies
Lampyridae•
Phylum: Arthopoda–
Class: Insecta
•
Order: Coleoptera–
Family: Lampyridae
•
80% of all species are arthopods•
40% of all insects are beetles
•
25% of all species are beetles•
About 2000 species in over 100 genera are called firefly or lightning bugs
Insects•
Body divided into head, thorax and abdomen
•
Thorax is three segmented; pro, meso
and meta.
•
Three pairs of legs•
Two pairs of wings
Coleoptera
•
Pro and pterathorax (fused meso
and meta
thorax)•
Fore wing hardened, elytra
•
Hind wing membranous
Light organ
Fifth Segment
Sixth Segment
Seventh Segment
Bioluminescence •
Simply, oxydation
of a specific organic substrate (four member
ring peroxide or linear hydroperoxide) by molecular oxygen•
Bioluminescence: widely used in organisms; bacteria, fungi, crustaceans, mollusks, fishes and insects.
•
Used for; communication, prey capture, predator evasion and burglar alarm hypothesis (?).
LuciferaseThe enzyme folds into two compact domains which are connected by a short flexible hinge. The larger N-terminal domain is composed of alternating ß-sheets and a-
helices to form a five-layered structure. The C-terminal portion of the protein forms a quite distinct domain but is much smaller. The two domains are separated by a wide cleft.
Luciferin
•
2-(6-hydroxybenzothiazol-2-yl)-2-thiazoline-4-carboxylic acid•
Only found in beetles
The reaction 1
•
In the first stage of the reaction both luciferin
and ATP form a complex with luciferase.
•
In the second step an acid anhydride (Fig. 1a) between the carboxylic group of luciferin
and AMP is formed (i.e. a luciferyl
adenylate), with the release of pyrophosphate (PPi).
The reaction 2
•
Through several intermediate stages, this adenylate
is oxidised, generating the cyclic peroxide, dioxetanone
(Fig. 1b-d).
The reaction 3
•
Decarboxylation
of this peroxide leads to formation of oxyluciferin
in a singlet electronically excited state that rapidly
decays to its ground state releasing a photon of light
Or simply
Luciferase
+ Luciferin
+ ATP Luciferase-Luciferin-AMP+ PPi
Luciferase-Luciferin-AMP
+ O2
Luciferase-Oxyluciferin*
+ AMP + CO2
Luciferase-Oxyluciferin* Luciferase-Oxyluciferin
+ Light
Mg++
Luciferin
Regenerating Enzyme
Cont…..•
Transformation of oxyluciferin
to 2-cyano-6-
hydroxybenzothiazole and •
Condensation of 2C6HB with D-cysteine
to yield luciferin
Communication •It is mainly utilized by adults as a means of species recognition and mating. Not all fireflies simply flash to grab the attention of potential mates, however; there are a variety of different methods by which fireflies can communicate with each other:
–
Both males and females produce photic
signals, often with a specific frequency, length, and interpulse
interval (IPI) (ex: Hotaria
parvula).–
The females, rather than the males, emit light -
in this case, males
fly around in the hopes of finding a sedentary, glowing female (ex: Microphotus).
–
The female is sedentary, and releases pheromones which are detected by males from longer distances. The female then glows so that the male can find her when he is within a closer range (ex: Pleotomus
pallens).
–
Some species of fireflies do not produce light at all, and instead rely solely on pheromones for communication (ex: Lucidota
atra).
•In any case, almost all male fireflies emit a species-specific signal while flying, which is reciprocated by the signal of a sedentary female.
Uses: BRET•
Bioluminescence Resonance Energy Transfer or BRET
•
BRET is a proximity-based assay where the energy generated by the catalytic degradation of coelenterazine
by the enzyme
Renilla
luciferase
(Rluc) (energy donor) is transferred to a green fluorescent protein (GFP) acting as the energy acceptor. The GFP then emits light at its specific emission wavelength.
How does it work?
In an experiment •
Lets say, you think protein A binds with protein B
•
You make a chimeric protein: protein A with renilla
luciferase•
And you make another chimeric protein: protein B with GFP
•
Remember GFP need excitation to glow•
You express both in a cell
•
You add coelenterazine
to the cells•
If protein A is near to protein B, then only you will see green light under microscope
You can also do luciferase
assayIt is a little complicated, so I’ll not discuss
here.
Polymorphism in Siphonophora
•
What is polymorphism?–
When you have more than one clearly different phenotype in one species of organism
•
What is siphonophora? –
Phylum: Coelentereta/Cnidaria
•
Class: Hydrozoa–
Order: Siphonophora
•
Although the syllabus says ‘polymorphism in siphonophora’, polymorphism is not limited to siphonophora. For example order Chondrophora
also have polymorphic species.
•
In this case the polymorphic animals cling together to form a colony and each individual of that colony is called ‘zooid’.
Coelenterata
or Cnidaria•
All aquatic
•
Radial symmetry•
Diploblastic body wall, epi
and gastrodermis
•
Have single internal cavity, Coelenteron, mouth at one end but without anal opening
•
Hydrostatic skeleton•
Nematocysts for defense
•
Free swimming larvae
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Nematocysts
SEM micrograph of nematocysts penetrating skin
•
Used for gathering food or defense
•
Contained in special cells called cnidocyte
•
Contains toxin
Basic forms•
Polyps: it is a tubular body with mouth, generally surrounded by tentacles.
•
Medusa: it is an upside down bowl or an umbrella shaped body with tentacles at the margin.
Patterns of polymorphism
•
Dimorphic: –
simplest form
–
Two kinds of zooids•
Gastrozooids
or
hydranths•
Gonozooids
or
blastocysts. These are formed asexually but produce sexual medusae
or gonophores –
Eg: Obelia, Tubularia, Campanularia
etc
Patterns of polymorphism •
Trimorphic: –
Three kinds of zooids
•
Gastrozooids•
Gonozooids
•
Dactylozooids, these are non-
feeding, defensive polyps with nematocysts
–
Eg: PlumulariaGoogle image without verification
Patterns of polymorphism •
Polymorphic:–
Have more than three types of individuals
–
Hydractinia
have 5 types•
Gastrozooids
•
Gonozooids•
Dactylozooids
•
Skeletozooids
with spiny chitin projection
•
Tentaculozooids
with sensory cells
Why do you need polymorphism?•
Division of labour
•
Each individual doing one function so that everybody don’t have to do all
•
What’s in it for everyone?•
Because each individual is generated asexually through budding, all the individuals in a colony in essence have the same genetic material.
Kotpal