S-nitrosylation in immunity and fertility: a general mechanism conserved in plants and animals
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Date
29/06/2013Author
Kanchanawatee, Krieng
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Abstract
Post-translational modification is an intracellular process that modifies the
properties of proteins to extend the range of protein function without spending
energy in de novo peptide synthesis. There are many post-translational modifications,
for example, phosphorylation, ubiquitination, and S-nitrosylation. S-Nitrosylation is a
post-translational modification which adds nitric oxide (NO) to sulfhydryl groups at
cysteine residues to form S-nitrosothiol (SNO), and is required for plant immunity
and fertility. Cellular NO changes between a pool of free NO and bound SNO.
During pathogen infection, nitrosative stress in plants is mainly controlled by Snitrosothiolglutathione
reductase (GSNOR) via the decomposition of GSNO.
GSNOR is an alcohol dehydrogenase type 3 (ADH3) which has both GSNOR and
formaldehyde dehydrogenase (FDH) activities. The roles of S-nitrosylation in
mammals overlap with those in plants. This conservation led us to explore the
relationship between S-nitrosylation, immune response, and fertility in Drosophila
melanogaster as it might prove to be a good genetic model for further analysis of the
role of S-nitrosylation in animals. I have identified fdh as the likely gsnor in D.
melanogaster and have knocked this out using an overlapping deficiency technique
in order to observe the effect on immunity and fertility. There are two main pathways
in the Drosophila innate immune response, the Toll pathway for protecting against
gram-positive bacteria and fungi, and the Imd pathway against gram-negative
bacteria. I have investigated the effect of removing GSNOR on sensitivity to gramnegative
bacteria (Escherichia coli and Erwinia carotovora) by septic and oral
infection, and to fungi (Beauveria bassiana). Susceptibility to infection by the gram
negative bacteria was similar to wild-type but susceptibility to B. bassiana was
increased. This increase in susceptibility correlated with reduced anti-fungal
antimicrobial peptide (AMP) production after B. bassiana infection. This suggests
that GSNOR might be required for the normal activity of the Toll pathway or novel
Toll-independent processes. We also observed that gsnor knockout impairs fertility
and development of embryos.