The document discusses extremophile plants that thrive in harsh environmental conditions. It provides examples of extremophile plants such as Arabidopsis halleri, which can hyperaccumulate heavy metals, and Thellungiella parvula, which is adapted to extreme salt and freezing conditions. The document also discusses how extremophile plants have developed genetic adaptations to stress conditions through mechanisms such as protective barriers, stress proteins, and metabolic adjustments. Extremophile plants provide insights into stress tolerance mechanisms and have applications in biotechnology due to novel enzymes they produce.
Genetic basis and evolution of heavy metal tolerance in plants
1. The role of harsh environments in
shaping plants' genomic patterns
Author: MICHAŁ SŁOTA
2. „It is not the strongest of the species that
survives, nor the most intelligent,
but rather the one most adaptable to change.”
Leon C. Megginson
Fot. Arabidopsis arenosa, Katowice (M. Słota)
3. Extremophile (from Latin extremus meaning "extreme" and Greek philiā
[φιλία] meaning "love") is an organism that thrives in physically or geochemically
extreme conditions that are detrimental to most life on Earth.
Extremophyte (from Latin extremus meaning "extreme" and Greek
phuton [φυτόν] meaning "plant ") plant able to survive in habitats of harsh conditions
and poor resources.
TERMS AND DEFINITIONS
mesophile/neutrophile
extremophile extremophile
[http://www.tutorvista.com/content/biology]
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2.
6. Evolution gradualism implies a weak selection acting
on polygenic variation.
Large-scale adaptation is often based on oligogenic
variation on crucial trait exposed to a strong natural
selection.
Simulated evolution in a multi-scale environment. Character
state is governed by alleles with additive effects at 10 loci
(mutation rate is 0.001 per locus per generation,
environmental variation adds a random variance σ2
E = 50).
Presented graphs show the population gene pool changes
tracking over different time-scales (a) 1000 generations,
(b) 10 000 generations, and (c) 100 000 generations. »
(Bell G., 2010)
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5.
MACRO- VS MICROEVOLUTION
"That natural selection always acts
with extreme slowness I fully admit."
(Darwin, 1859)
8. Possible models for the evolution of
extremophiles.
(A), extremophiles are pioneer organisms
colonising an extreme but widespread
environment. As the difficulties of living in
the new environment are resolved,
organisms become widespread in
this environment.
(B), extremophiles are pioneer organisms
colonising an extreme and rare
environment. The environment remains
rare and the organisms continue to be
considered extreme.
(C), extremophiles that benefited from
changes of conditions during the
geological evolution of Earth, adapted
firmly and colonised majority of habitats.
(Wharton 2002)
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7.
10. Słota, 2013
9.
EXTREMOPHILES- UNCOMMON ORIGIN
« Phylogenetic tree of
procaryotes of known genome.
Extremophiles are marked bold.
(Xu and Glansdorff, 2002)
11. METABOLIC ADJUSTMENT
(eg. active detoxication/excretion, osmotic
adjustment, adjustment of metabolic rates)
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10.
MECHANISMS OF ADAPTATIONS
PROTECTIVE BARRIERS
(eg. membrane composition, exudates)
STRESS NEUTRALIZATION
(eg. antioxidative defense, stress proteins
and chaperones, chelating agents)
12. Słota, 2013
10.
EXTREMOPHILES- RISE OF INTEREST
« M. jannaschii
EXTREMOPHILES
Thermophile
Methanococcus jannaschii
Methanocaldococcaceae
(Bult et al. 1996)
Methanococcus jannaschii
▪ thermophilic methanogenic archaea in the class
Methanococci,
▪ capable of growth on carbon dioxide and hydrogen
as primary energy sources
▪ lives near hydrothermal vents 2,600 meters below
sea level,
▪ M. jannaschii was the fourth free-living organism to
be completely sequenced (1996),
▪ its genome includes many hydrogenases, such as a
5,10-methenyltetrahydromethanopterin hydrogenase,
a ferredoxin hydrogenase (eha), and a coenzyme
F420 hydrogenase,
▪ proteomic studies showed that M. jannaschii contains
a large number of specific inteins (internal protein
elements that self-excise from their host protein and
catalyze ligation of the flanking sequences).
13. Arabidopsis halleri
✓ closely related to A. thaliana with a similar genome
size,
✓ is a stoloniferous perennial herb with a disjunct
distribution in Europe and eastern Asia,
✓ populations are found in grassy meadows, forest
margins, as well as rocky slopes,
✓ grows on acidic, neutral and oligotrophic soils, but
also on soils with a high heavy metal content,
✓ tolerant of zinc and cadmium and can
hyperaccumulate these heavy metals in above-
ground tissues up to 100 times the critical toxicity
level of closely related, non-tolerant Arabidopsis
species.
✓ high expression of genes encoding metal
transporters (e.g. ZIP9, MTP1) and enzymes for
chelator synthesis (e.g. NA).
« A. halleri rosette
(phot. M. Słota).
EXTREMOPHILES
Metalophyte
Arabidopsis halleri
Brassicaceae
Transcriptional responses of selected A. halleri Zn tolerance candidate genes.
Relative transcript levels (RTLs) showni with color indexes (Talke et al. 2006).
Zinc hyperaccumulation and hypertolerance
mechanisms in A. halleri and N. caerulescens.
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11.
14. EXTREMOPHILES – metalophyte rates of microevolution
Estimated rates of evolution estimated from different studies (Bone and Farres 2001).
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12.
15. Thellungiella parvula
▪ diploid species of the Brassicaceae family
▪ genome size similar (~15% larger) to A. thaliana,
consists of 7 chromosomes,
▪ adapted to extreme salt and freezing conditions,
▪ Thellungiella spp. continue to grow at salinities up to
500 mM NaCl,
▪ whole genome sequencing identified a number of
tandem duplications that, by the nature of the
duplicated genes, suggest a possible basis for T.
parvula's extremophile lifestyle,
▪ higher copy numbers of orthologous genes related to
stress adaptation, such as AVP1 (vacuolar H+-
pyrophosphatase), HKT1 (high-affinity K+ transporter1),
NHX8 (sodium/hydrogen exchanger 8), CBL10
(calcineurin b-like 10) and MYB47.
« T. parvula habitat.
EXTREMOPHILES
Psychrophile
Halophile
Thellungiella parvula
Brassicaceae
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13.
Comparison of the GO 'biological processes' (A) and 'molecular
function' categories (B) between T. parvula ORFs and A. thaliana
cDNAs for genes showing tandem duplications. The radial axes are the
percentages of cDNA or ORFs in each GO (Dassanayake et al. 2011).
A.B.
Mechanism of an effective exclusion of Na+
from the Shoot of Thellungiella achieved
through the combined action of a Voltage-
Independent Channel (VIC) and a Na+/H+
Antiporter (SOS1). »
16. Selaginella lepidophylla
(rose of Jericho, resurrection plant)
▪ species of desert plant of the spikemoss family
(Selaginellaceae),
▪ native to the Chihuahuan Desert (Mexico),
▪ ability to survive almost complete desiccation,
▪ during dry weather in its native habitat, its stems curl
into a tight ball and uncurl when exposed to moisture
(cryptobiosis),
Metabolic profiling results
▪ S. lepidophylla retaines higher amounts of sucrose,
mono- and polysaccharides and sugar alcohols,
▪ aromatic amino acids, osmoprotectant (eg. betaine)
and flavonoids are more abundant,
▪ High levels of γ-glutamyl amino acid, linked with
glutathione metabolism in the detoxification of
reactive oxygen species. (Yobi et al. 2012)« S. lepidophylla
reviving, duration 3h.
EXTREMOPHILES
Dehydratation tolerant
Selaginella lepidophylla
Selaginellaceae
« Most abundantly represented transcripts in the 2.5 h dehydrated
S. lepidophylla cDNA library (Iturriaga et al. 2006).
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14.
17. Glycine max
▪ soybeans growth was observed inside the 30-
kilometer restricted zone, just 5 kilometers from the
remains of Chernobyl Nuclear Power Plant,
▪ soil was significantly contaminated with long-living
radioisotopes, such as 137Cs (163 times higher value
than control),
Proteomic analysis results
▪ 9.2% of 698 quantified protein spots on 2-D gel were
found to be differentially expressed,
▪ beans from the high-radiation area had three times
more cysteine synthase (involved also in heavy metal
binding),
▪ beans contained also 32% more betaine aldehyde
dehydrogenase (involved in chromosomal
abnormalities reduction),
▪ seed storage proteins concentracion differed.«A soybean plant grows
in a contaminated field
near Chernobyl..
EXTREMOPHILES
Radioresistant
Glycine max
var. Soniachna
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15.
(Danchenko et al. 2009)
Functional classification of the 211 soybean proteins with paired
abundances between soybean seed development
in non-radioactive and radioactive Chernobyl fields.
18. (Horikoshi and Bull, 2011)
Alkaline proteases, derived
from alkaliphilic species,
constitute an important
group of enzymes that find
applications primarily as
protein-degrading additives
in detergents.
EXTREMOPHILE USES AND APPLICATIONS
One of the most widely
known applications of an
extremophile product -
thermostable DNA
polymerase.
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16.
19. A number of angiosperm families include extremophile species,
although only fewer than 10% of all plant species may be classified this
way.
Extremophiles’ presence in evolutionarily distinct lineages reveals genetic
complexities that appear to have evolved from the common genetic
background under extremely high selective pressure.
Knowledge about how extremophiles face extreme environmental
pressurre, can contribute to the expansion of knowledge about
underlying genetic requisites and mechanisms for successful stress
defenses of mesophile plants.
Extremophiles can serve as a source of novel enzymes for industrial
application and therapeutics of a specific and unique function.
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17.
20. ▪ Bell, G. 2010. Fluctuating selection: the perpetual renewal of adaptation in variable
environments. Phil. Trans. R. Soc. B 365, 87–97
▪ Bult C.J. et al. 1996. Complete genome sequence of the methanogenic archaeon,
Methanococcus jannaschii. Science 273 (5278): 1058-1073
▪ Danchenko M, Skultety L, Rashydov NM, Berezhna VV, Mátel L. 2009. Proteomic analysis of
mature soybean seeds from the Chernobyl area suggests plant adaptation to the
contaminated environment. J Proteome Res 8: 2915–2922
▪ Dassanayake, M., D.H. Oh, J.S. Haas, A. Hernandez, H. Hong, S. Ali, D.J. Yun, R.A.
Bressan, J.K. Zhu and H.J. Bohnert. 2011. The genome of the extremophile crucifer
Thellungiella parvula. Nat Genet 43: 913-918
▪ Flegr, J. 2013. Microevolutionary, macroevolutionary, ecological and taxonomical implications
of punctuational theories of adaptive evolution. Biology Direct, 8: 1-14
▪ Hanikenne, M. and C. Nouet. 2011. Metal hyperaccumulation and hypertolerance: a model
for plant evolutionary genomics. Curr. Opin. Plant Biol. 14: 252–259
▪ Horikoshi, K., G. Antranikian, A.T. Bull, F.T. Robb, K.O. Stetter (Eds.) 2011. Extremophiles
Handbook. Springer Reference, Vol. 1 and 2
▪ Iturriaga, G., M.A. Cushman and J.C. Cushman. 2006. An EST catalogue from the
resurrection plant Selaginella lepidophylla reveals abiotic stress-adaptive genes. Plant
Sci.170:1173-1184
▪ Talke, I.N., M. Hanikenne and U. Krämer. 2006. Zn-dependent global transcriptional control,
transcriptional de-regulation and higher gene copy number genes in metal homeostasis of
the hyperaccumulator Arabidopsis halleri. Plant Physiol 142: 148–167
▪ Wharton, D. 2002. Life at the Limits: Organisms in Extreme Environments. David A.
Cambridge University Press 2002
▪ Xu, Y. and N. Glansdorff. 2002. Was our ancestor a hyperthermophilic procaryote? Comp.
Biochem. Physiol., Part A: Mol. Integr. Physiol. 133, 677-688
▪ Yobi, A., B. W. Wone, X. Wenxin, D.C.Alexander, G. Lining, J.A. Ryals, M.J. Oliver and J.C.
Cushman. 2012. Comparative metabolic profiling between desiccation-sensitive and
desiccation-tolerant species of Selaginella reveals insights into the resurrection trait Plant J.
72 (6): 983-999
