Title: Desiccation Tolerance Mechanisms and Evolution
1Desiccation ToleranceMechanisms and Evolution
Mel Oliver and Brent Mishler
2Desiccation-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
3Types 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.
4Desiccation-tolerant Plants.
- Desiccation-tolerant
- ALGAE
- LICHENS
- BRYOPHYTES
- Modified Desiccation-tolerant
- FERNS
- ANGIOSPERMS
5Distribution of Desiccation Tolerance in the
Plant Kingdom
Angiosperms
conifers
cycads
ferns
gnetophytes
Equisetum
Gingko
Selaginella
Isoetes
Lycopodium
mosses
hornworts
liverworts
Seed Plants
Tracheophytes
Land Plants
Oliver, Tuba and Mishler 2000
6Tortula ruralis
7Selaginella
Selaginella bigelovii
8Polypodium virginianum
9Orthodox Seeds
10Distribution of Desiccation tolerance in the
Angiosperms
Cyperaceae
Labiatae
Poaceae
Scrophulariaceae
Gesneriaceae
Velloziaceae
Liliaceae
Hamameliales
Magnoliales
renunculids
Angiosperms
Oliver, Tuba and Mishler 2000
11Xerophyta villosa
12Myrothamnus flabellifolia
13Craterostigma wilmsii
14Xerophyta viscosa
15Sporobolus stapfianus
16Craterostigma plantagineum
Hydrated
Dry
Rehydrated
17Critical Parameters for Desiccation-tolerance.
- Limit damage to a repairable level
- Maintain physiological integrity in the dry
state - Mobilize repair mechanisms upon rehydration
Bewley 1979
18Essence of Desiccation-tolerance.
Cellular Repair
Cellular Protection
19Bryophyte Model
RAPID WATER LOSS Constitutive Cellular Protection
Hormone ?
Induction of Recovery and Repair Mechanisms
Hydrated
Dry
Rehydrated
20Angiosperm Model
SLOW WATER LOSS Induction of Cellular Protection
ABA
Re-establishment Processes
Hydrated
Dry
Rehydrated
21Postulated Evolutionary History of Desiccation
Tolerance in Land Plants
Angiosperms
conifers
cycads
ferns
gnetophytes
Inducible protection (repair?) and
later poikilochlorophylly
Equisetum
Gingko
Selaginella
Isoetes
Lycopodium
S
mosses
Developmentally programmed protection - propagules
hornworts
liverworts
Inducible protection plus repair?
T
Developmentally programmed protection - spores?
Constitutive protection and repair
Loss of vegetative desiccation tolerance in the
ancestral lineage
Oliver, Tuba and Mishler 2000
22Bryophyte Model
RAPID WATER LOSS Constitutive Cellular Protection
Hormone ?
Induction of Recovery and Repair Mechanisms
Hydrated
Dry
Rehydrated
23Tr 288 Phylogenetic Gene Search
Tr 288 Gene
Expected PCR Products
(Sequence for Identity)
GPN-Box Consensus primers
24(No Transcript)
25Unrooted Tortula Phylogenetic Network Occurance
of Tr288 Orthologs
Probable tree root
Calyptopogon
288
Tortula papillosa
288
Tortula sinensis
288
Tortula muralis
288
Tortula andersonii
288
288
Tortula indet NSW
Tortula handelii
288
Tortula amphidiacea
288
Tortula subaristata
288
Tortula ruralis
Tortula caninervis
288
288
Tortula cavelii
288
26Unrooted Deep Green Phylogenetic
Network Occurance of Tr288 Orthologs
Riccia frostii
Riccia membranacea
Riccia albolimbata
Riccia sulivantii
Riccia atromarginata
Targionia
Riccia albida
Lunularia
Asterella
Probable Network Root
Lophocolea
Blasia
algal ancestor
Haplomitrium
Osmunda
Equisetum
288
Angiopteris
Notothylas
Megaceros
Psilotum
288
Anthoceros
Sequoia
Anthoceros fusiformis
Selaginella
Sphagnum palustre
288
Huperzia
Sphagnum cuspidatum
Isoetes
Tetraphis
288
Polytrichum piliferum
Pterogonium
Buxbaumia
288
Polytrichum commune
Exostratum
Funaria
Octoblepharum
288
Grimmia
Leucophanes
288
Calyptopogon
Arthrocormus
Tortula ruralis
288
Mitthyridium
288
Tortula princeps
Tortula muralis
288
288
27Phylogenetic Approachto 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
28Deep change in function
A phylogenetically distant comparison large
background differences
29Recent Change in function
A phylogenetically close comparison low
background differences
30Increasing complexity
Ancestor-descendant comparison using reconstructed
ancestral states