Desiccation Tolerance Mechanisms and Evolution Mel Oliver and Brent Mishler.

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1 Desiccation Tolerance Mechanisms and Evolution Mel Oliver and Brent Mishler

2 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

3 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.

4 Desiccation-tolerant Plants.  Desiccation-tolerant  ALGAE  LICHENS  BRYOPHYTES  Modified Desiccation-tolerant  FERNS  ANGIOSPERMS

5 Distribution of Desiccation Tolerance in the Plant Kingdom liverworts hornworts mosses Selaginella Isoetes Lycopodium Equisetum ferns Gingko cycads conifers gnetophytes Angiosperms Land Plants Tracheophytes Seed Plants Oliver, Tuba and Mishler 2000

6 Tortula ruralis

7 Selaginella Selaginella bigelovii

8 Polypodium virginianum

9 Photo Courtesy of Dr Christina Walters USDA NSSL Fort Collins Orthodox Seeds

10 Distribution of Desiccation tolerance in the Angiosperms Poaceae Cyperaceae Velloziaceae Liliaceae Magnoliales renunculids Hamameliales Labiatae Gesneriaceae Scrophulariaceae Angiosperms Oliver, Tuba and Mishler 2000

11 Xerophyta villosa

12 Photo Courtesy of Dr. Jill Farrant and Clare Vander Willegen University of Cape Town SA Myrothamnus flabellifolia

13 Craterostigma wilmsii

14 Xerophyta viscosa

15 Sporobolus stapfianus

16 Photos Courtesy of Dr. Dorothea Bartels University of Bonn Craterostigma plantagineum Dry Rehydrated Hydrated

17 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

18 Essence of Desiccation-tolerance. Testable Hypothesis Cellular Repair Cellular Protection

19 Bryophyte Model Dry Rehydrated Hydrated RAPID WATER LOSS Constitutive Cellular Protection Protection Induction of Recovery and Repair Mechanisms Hormone ?

20 Angiosperm Model SLOW WATER LOSS Induction of Cellular Protection Re-establishmentProcesses Dry Rehydrated Hydrated ABA

21 Postulated Evolutionary History of Desiccation Tolerance in Land Plants hornworts mosses Selaginella Isoetes Lycopodium Equisetum ferns Gingko cycads conifers gnetophytes Angiosperms liverworts Constitutive protection and repair Inducible protection plus repair? Developmentally programmed protection - propagules Developmentally programmed protection - spores? Inducible protection (repair?) and later poikilochlorophylly T S Loss of vegetative desiccation tolerance in the ancestral lineage Oliver, Tuba and Mishler 2000

22 Bryophyte Model Dry Rehydrated Hydrated RAPID WATER LOSS Constitutive Cellular Protection Protection Induction of Recovery and Repair Mechanisms Hormone ?

23 ABCDEFGHIJKLMNO In 1 2 Dhy EFGH Tr 288 Phylogenetic Gene Search Tr 288 Gene GPN-Box Consensus primers Expected PCR Products (Sequence for Identity)

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25 Tortula ruralis Tortula sinensis Tortula andersonii Tortula indet NSW Tortula amphidiacea Tortula subaristata Tortula caninervis Tortula cavelii Tortula handelii Tortula muralis Tortula papillosa Calyptopogon 288 Probable tree root Unrooted Tortula Phylogenetic Network Occurance of Tr288 Orthologs

26 Equisetum Osmunda Angiopteris Sequoia Selaginella Huperzia Isoetes Polytrichum piliferum Polytrichum commune Funaria Grimmia Tortula ruralis Tortula princeps Tortula muralis Arthrocormus Leucophanes Octoblepharum Exostratum Pterogonium Sphagnum cuspidatum Sphagnum palustre Anthoceros fusiformis Anthoceros Megaceros Notothylas Blasia Asterella Riccia albida Riccia atromarginata Riccia albolimbata Riccia frostii Riccia membranacea Riccia sulivantii Targionia Lunularia Lophocolea algal ancestor 288 Mitthyridium 288 Calyptopogon 288 Probable Network Root Psilotum Buxbaumia Tetraphis Haplomitrium Unrooted “Deep Green” Phylogenetic Network Occurance of Tr288 Orthologs

27 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

28 Deep change in function in function A phylogenetically distant comparison = large background differences

29 A phylogenetically close comparison = low background differences Recent Change in function in function

30 Increasing complexity Ancestor-descendant comparison using reconstructed ancestral states