Shannon, Adam J. and Browne, John A. and Boyd, Jacqueline and Fitzpatrick, David A. and Burnell, Ann M.
The anhydrobiotic potential and molecular phylogenetics of species and strains of Panagrolaimus (Nematoda, Panagrolaimidae).
Journal of Experimental Biology, 208.
Members of the genus Panagrolaimus are bacterialfeeding
nematodes that occupy a diversity of niches
ranging from Antarctic and temperate soils to terrestrial
mosses. Some members of this genus are able to survive
extreme desiccation by entering into a state of suspended
animation known as anhydrobiosis. We have assembled a
collection of Panagrolaimus species and strains and have
investigated their anhydrobiotic phenotypes. Our data
show that within the genus Panagrolaimus there is a
continuum of strains ranging from those unable to survive
exposure to low relative humidity (RH) without prior
preconditioning at high RH (slow desiccation strategists),
through strains that have limited ability to survive rapid
desiccation but whose anhydrobiotic ability improves
upon preconditioning, to strains such as P. superbus that
can readily survive immediate exposure to severe
desiccation (fast desiccation strategists). Using this panel
of nematodes we investigated the effect of preincubation at
high RH on the accumulation of trehalose and on the
nematodesâ anhydrobiotic potential. We found that there
is a strong correlation between trehalose induction and
anhydrobiotic survival in Panagrolaimus. Furthermore,
the high trehalose levels observed in fully hydrated P.superbus (10% dry mass) suggest that constitutive
expression of trehalose pre-adapts this fast dehydration
strategist to combat desiccation. All the strains observed,
regardless of survival rates, undertook both coiling and
clumping, which has the effect of reducing surface area
and slowing the rate of water loss during desiccation.
Phylogenetic analyses were carried out to investigate
whether the observed anhydrobiotic phenotypes were the
result of convergent evolution or represented a single
phylogenetic lineage. These analyses, derived from
alignments of the rDNA ITS and D3 sequences, indicate
that the strongly anhydrobiotic strains of Panagrolaimus
form a single phylogenetic lineage, which is separate
from the weakly anhydrobiotic strains. The weakly
anhydrobiotic strains are also phylogenetically divergent
from each other. Our data indicate that Panagrolaimus
has the potential to be an excellent model system for the
investigation of molecular aspects of nematode anhydrobiosis.
||Panagrolaimus, nematode, anhydrobiosis, desiccation, trehalose, phylogeny, rDNA ITS, rDNA D3.
||Science & Engineering > Biology
Prof. Ann Burnell
||04 May 2007
|Journal or Publication Title:
||Journal of Experimental Biology
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