Worm Breeder's Gazette 15(1): 35 (October 1, 1997)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Paraquat mediates differential gene expression in C. elegans

Wilson Tawe, Marie-Luise Eschbach, Rolf D. Walter, Kimberly Henkle-Duehrsen

Bernhard Nocht Institute for Tropical Medicine, Bernhard Nocht Str. 74, 20359 Hamburg, Germany

        In order to identify genes that are differentially expressed as
a consequence of stress due to paraquat, we used the differential
display technique (1) to compare mRNA expression patterns in
Caenorhabditis elegans. A C. elegans mixed-stage worm population, as
well as a homogeneous larval population were treated with 100 mM
paraquat, parallel to controls. Over 50 mRNA species that are
potentially up-regulated in response to paraquat were identified.
Sixteen of these candidates were re-amplified, ligated into plasmid
vectors and the nucleotide sequences were determined. The induction of
four of these expressed sequence tags (ESTs) designated L1, M47, M96
and M132 were confirmed in two independent stress / differential
display experiments, as well as by northern blot analysis with RNA from
stressed and unstressed worms.
        The nucleotide sequences of the independently isolated L1 and
M47 ESTs were found to be identical. Their corresponding mRNA level
increased more than 40-fold in the larval stage, and to a lesser extent
in the mixed-stage worm population, in response to paraquat. Induction
levels of 3 - 5 fold were observed for the M132 and M96 ESTs, in both
larval and mixed populations. All of the isolated ESTs showed homology
to portions of the C. elegans cosmids. The L1/M47 EST is derived from a
gene encoding one of the putative C. elegans glutathione
S-transferases. The paraquat-inducible M132 EST was also identified,
and encodes a putative C2H2 - type zinc finger protein, possessing an
N-terminal leucine zipper. However, the M96 EST appears to be a novel
gene whose product has not yet been identified. Searches of other
eukaryotic nucleotide sequence databases did not reveal any significant
homologies to known sequences from any organism.
        Since paraquat is known to generate superoxide radicals in
vivo, and the cellular superoxide dismutase (SOD) enzyme complex is
responsible for the quenching of the deleterious effects of these
radicals, the response of the C. elegans superoxide dismutases (2,3,4)
to paraquat was also investigated in this study. Northern blot
experiments demonstrated that mRNA steady state levels of the C.
elegans manganese type and the copper/zinc type superoxide dismutases
increased two-fold in response to paraquat, in the larval population.
In contrast, mixed-stage populations did not show any apparent increase
in the levels of these SOD mRNAs in response to paraquat.

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