Candida Infection Biology – fungal armoury, battlefields ... - FINSysB

Poster number: 08
Histidine kinase Sln1 interferes with mitochondrial
functions of Candida albicans
Rabeay Y.A. Hassan, Anna Buschart, and Ursula Bilitewski*
Helmholtz Centre for Infection Research, Biological Systems Analysis, Inhoffenstr. 7, 38124
Braunschweig, Germany. rabeay.hassan@helmholtz-hzi.de
In the pathogenic fungus Candida albicans, three histidine kinases (HK) have been
identified: Sln1p, Cos1p (also known as Nik1p) and Chk1p. They are involved in the
adaptation to stress, growth, morphogenesis and sensitivity to several antifungal
compounds. Deletion of SLN1 does not affect cell viability in rich media and only
slightly affects the tolerance to osmotic stress.
However, we show for the first time that deletion of the SLN1 perturbs mitochondrial
functions. The oxygen uptake rates of the three HKs deletion mutants, ∆sln1, ∆chk1
and ∆cos1 were measured and a faster rate of oxygen consumption was observed
in sln1 than in the wild-type. This can be explained by the up-regulated expression
of the alternative oxidase AOX2 in sln1, indicating that the alternative respiratory
pathway is activated in addition to the presence of the classical respiratory chain
(CRC). The alternative oxidative pathway is usually activated in response to
inhibitors of the CRC.
Rotenone-treatment of the wild type strain stimulated the production of reactive
oxygen species (ROS) and inhibited the reduction of dichlorophenolindophenol
(DCIP-complex I activity assay). However, rotenone had no or only a small effect
on the ROS production and the inhibition of the DCIP reaction in sln1. These
findings point to a low activity of complex I in sln1. This conclusion was supported
by whole-genome gene expression analysis, which showed a down-regulation of
genes encoding components of the mitochondrial NADH:ubiquinone
oxidoreductase complex (Complex I), namely NAD3, NAD4 and NAD5 in addition
to subunits of cytochrome c oxidase (complex IV) (COX2 and COX5) in sln1.
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