Chemical ecology of
tropical algae:
Part I
Bernardo A.P. da Gama
Universidade Federal Fluminense
Niterói – Rio de Janeiro - Brazil
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Outline
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The tropical marine environment
What is seaweed chemical ecology?
What are secondary metabolites?
How are they biosynthesized?
Why are they biosynthesized?
Ecological roles of macroalgal metabolites
Resource allocation models
Defenses against herbivores
Defenses against epibionts
caulerpenyne
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Part I
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The tropical marine environment
What is seaweed chemical ecology?
What are secondary metabolites?
How are they biosynthesized?
Why are they biosynthesized?
Ecological roles of macroalgal metabolites
Resource allocation models
Defenses against herbivores
Defenses against epibionts
caulerpenyne
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References
• Few books, majority of knowledge is hot out of the press!
• Consequence of the novelty of this expanding field
Ecological
roles of
marine natural
products
Edited by
Valerie J. Paul
Springer
CRC Press
2008
2001
Comstock Publishing
1992
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The tropical marine environment
• Conspicuous and diverse coral reefs are
NOT the only tropical ecosystems!
• Seagrass beds, rocky shores, mangrove
forests – equally important
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The tropical marine environment
• How to define it?
• Latitude: between 23o27’ N and S
• SST: sea surface temperatures – more
accurate indication
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The tropical marine environment
Consider this:
• Macroalgae are restricted to the euphotic zone
• Present boundaries are set by SS isotherms (20oCwinter isotherms)
• Presence of hard substrata is a condition for most
macroalgae
• Present distribution results from migration &
displacement of coastlines along geological times
(continental drift)
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The tropical marine environment
• Add to this the recent (~500 y.a.) human-mediated
amplification of distributions – bioinvasions
• Further human-mediated changes are to be expected if
global climatic changes really affect global oceanic
currents!
Sea Surface Temperature, MODIS satellite data, NASA, GSFC
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What is algal chemical ecology?
• Science that studies any type of ecological
interaction involving marine algae
mediated by chemical compounds
• E.g.: herbivory, competition, gamete
attraction, symbiosis, epibiosis, settlement,
etc.
capisterone A, R = COCH3
capisterone B, R = H
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What are secondary metabolites?
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Also called natural products
Not involved in primary cell functions
Thus called secondary metabolites
Specific or mixed biosynthetic pathways
Many are group- or even species-specific
Please read
Faulkner yearly reviews
and later Blunt et al. entitled
“Marine natural products”
In Natural Product Reports
phlorotannins
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How are they biosynthesized?
Maschek & Baker (2008)
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Isoprenoids
• Mevalonate-dependent & independent
OH
OH
quinones
terpenes
O
O
HO
carotenoids
steroids
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Acetogenins
OH
HO
S
O
O
O
O
Polyketides
O
polyphenolics (phlorotannins)
O
O
HO
OH
O
O
OH
O
OH
OH
O
OH
fatty acids
prostaglandins
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Amino acids
OH
O
HN
NH
N
O
H
N
O
H
N
O
O
Br
NH
O
peptides
O
N
H
N
alkaloids
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Shikimate pathway
O
HO
HO
H
H
NH
H
OH O
H
O
O
O
H
HO
flavonoids
O
O
HO
O
O
S
OH
O
cinnamic acid derivatives
(seagrasses)
O
O
O
OH
coumarins
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Nucleic acids
NH2
C N
N
O
N
N
HO
N
N
O
HN
N
N
H
OH OH
nucleotid base
modified nucleic acid
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Carbohydrates
HO
HO
HO
HO
O
OH
OH
S
HO
O
HO
O
OH
OH
OH
sugar
polysaccharide
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Why are they biosynthesized?
• If you discover, please let me know!
• Some claim they are just “metabolic waste
products”
• Some are clearly involved in basic, nonecological roles (e.g., phlorotannins)
• Makes no sense to invest in genetic
information, enzymes and precursors to
synthesize them if they play no function!
• Chemical communication and warfare
Williams DH (1989) Why are secondary metabolites (natural products) biosynthesized? J Nat Prod
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Intraspecific molecular interactions
SEXUAL
AUTOTOXINS
ALARM
AUTOINHIBITORS
TRACK / CUE
PHEROMONES
GROUPING
TERRITORIAL
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Interspecific molecular interactions
SYMBIONT LOCALIZATION
KAIROMONES
PREY LOCALIZATION
ALARM / CUE
benefit the receiver of the chemical message
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Interspecific molecular interactions (II)
ALLOMONES
ATTRACTION
REPELLENT
DEFENSE
ANTIBIOTIC
COMPETITION
POISON
benefit the sender of the message
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Energy
source
sexual
UV protection
feromones
Consumption
antiFouling
Pathogens
Bacteria
Algae
Fungi
Alellopathy
simbiosis
Invertebrates
& fish
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