Transcript A Bryophyte Trackable Marker for the Evolution of

Desiccation Tolerance
Mechanisms and Evolution
Mel Oliver and Brent Mishler
Desiccation-tolerance.
The ability to revive from the air-dried
state (the air being of low relative
humidity) thus experiencing protoplasmic
dehydration without suffering permanent
injury
 Bewley and Krochko. 1982
Types of Desiccation-tolerance.
 Plants whose tolerance to water loss is low.
 Plant structures that are adapted to withstand
desiccation and for which water loss is an expected
event. - seeds.
 Plants that are capable of tolerating desiccation
regardless of the rate at which water loss occurs.
 Plants that are capable of tolerating desiccation only
if water loss is a slow process.
Desiccation-tolerant Plants.
 Desiccation-tolerant
 ALGAE
 LICHENS
 BRYOPHYTES
 Modified Desiccation-tolerant
 FERNS
 ANGIOSPERMS
Distribution of Desiccation Tolerance in the
Plant Kingdom
ferns
Equisetum
Selaginella
cycads
conifers
gnetophytes
Angiosperms
Gingko
Isoetes
Lycopodium
mosses
hornworts
liverworts
Seed Plants
Tracheophytes
Land Plants
Oliver, Tuba and Mishler 2000
Tortula ruralis
Selaginella
Selaginella bigelovii
Polypodium virginianum
Orthodox Seeds
Photo Courtesy of Dr Christina Walters USDA NSSL Fort Collins
Distribution of Desiccation tolerance in the Angiosperms
Cyperaceae
Labiatae
Poaceae
Gesneriaceae
Velloziaceae
Liliaceae
Magnoliales
Hamameliales
renunculids
Oliver, Tuba and Mishler 2000
Angiosperms
Scrophulariaceae
Xerophyta villosa
Myrothamnus flabellifolia
Photo Courtesy of Dr. Jill Farrant and Clare Vander Willegen University
of Cape Town SA
Craterostigma wilmsii
Xerophyta viscosa
Sporobolus stapfianus
Craterostigma plantagineum
Hydrated
Dry
Rehydrated
Photos Courtesy of Dr. Dorothea Bartels University of Bonn
Critical Parameters for
Desiccation-tolerance.
 Limit damage to a repairable level
 Maintain physiological integrity in
the dry state
 Mobilize repair mechanisms upon
rehydration
Bewley 1979
Essence of Desiccation-tolerance.
Testable Hypothesis
Cellular
Repair
Cellular
Protection
Bryophyte Model
RAPID WATER LOSS
Constitutive Cellular
Hormone ?
Protection
Induction of
Recovery and Repair
Mechanisms
Hydrated
Dry
Rehydrated
Angiosperm Model
SLOW WATER LOSS
Induction of
ABA
Cellular Protection
Re-establishment
Processes
Hydrated
Dry
Rehydrated
Postulated Evolutionary History of Desiccation
Tolerance in Land Plants
Equisetum
Selaginella
ferns
cycads
Angiosperms
conifers
gnetophytes
Inducible protection
(repair?) and later
poikilochlorophylly
Gingko
Isoetes
Lycopodium
mosses
hornworts
liverworts
S
Developmentally programmed
protection - propagules
T
Inducible protection plus repair?
Developmentally programmed
protection - spores?
Constitutive protection and repair
Oliver, Tuba and Mishler 2000
Loss of vegetative
desiccation tolerance
in the ancestral lineage
Bryophyte Model
RAPID WATER LOSS
Constitutive Cellular
Hormone ?
Protection
Induction of
Recovery and Repair
Mechanisms
Hydrated
Dry
Rehydrated
Tr 288 Phylogenetic Gene Search
Dhy
Tr 288 Gene
In
1 A
B C D E F G H I J K L MN
O
In
2
Expected
PCR Products
(Sequence for
GPN-Box
Consensus
primers
Identity)
E
F
G
H
Unrooted Tortula Phylogenetic Network
Probable tree root
Occurance of Tr288 Orthologs
Calyptopogon
288 Tortula papillosa
288
Tortula sinensis 288
288 Tortula muralis
Tortula andersonii 288
Tortula indet NSW 288
288 Tortula handelii
Tortula amphidiacea 288
Tortula subaristata 288
288 Tortula ruralis
Tortula caninervis 288
Tortula cavelii
288
Unrooted “Deep Green” Phylogenetic Network
Occurance of Tr288 Orthologs
Riccia frostii
Riccia membranacea
Riccia albolimbata
Riccia sulivantii
Riccia atromarginata
Targionia
Riccia albida
Asterella
Blasia
Haplomitrium
Notothylas
Megaceros
Lunularia
algal ancestor
Equisetum
Sphagnum palustre
Exostratum
Octoblepharum
Huperzia 288
Isoetes
Polytrichum piliferum
Buxbaumia
Polytrichum commune
Funaria
Grimmia 288
Leucophanes
Calyptopogon 288
Arthrocormus
Tortula ruralis
288
288 Mitthyridium
Tortula
princeps
Tortula muralis
288
288
288
288
Sequoia
Selaginella
Anthoceros fusiformis
Tetraphis
Pterogonium
Osmunda
Angiopteris
Psilotum
Anthoceros
Sphagnum cuspidatum
Probable Network Root
Lophocolea
288
288
Phylogenetic Approach
to Functionality
 Establishment of a correlation between the presence
of a gene and a specific phenotype
 Establishment of the role of a gene in the evolution of
a particular phenotype
 Establishment of the importance of a particular
mechanism in the evolution of a particular phenotype,
e.g., induced repair upon rehydration versus induced
protection during drying in desiccation-tolerance
Collaboration with Brent Mishler - UC Berkeley
Deep change
in function
A phylogenetically distant comparison
= large background differences
Recent Change
in function
A phylogenetically close comparison
= low background differences
Increasing complexity
Ancestor-descendant comparison using
reconstructed ancestral states