Depletion of a polo-like kinase and manipulation of the cell cycle
trigger hyphal growth in Candida albicans .
Catherine
Bachewich (1), David Thomas (2), Malcolm Whiteway (3)
(1)
Health Sector, Biotechnology Research Institute, National Research
Council of Canada, 6100 Royalmount Ave., Montreal, Quebec, H4P 2R2,
Canada; (2) Department of Biochemistry, McGill University, Montreal,
Quebec, H3G 1Y6, Canada; (3) Health Sector, BRI/NRC, 6100 Royalmount
Ave., Montreal, H4P 2R2, Canada
Morphogenesis in the fungal pathogen
Candida albicans is an important virulence-determining factor,
since the ability to switch from a yeast to a hyphal growth form is
associated with increased pathogenesis. We previously identified a cell
cycle regulatory polo-like kinase in Candida albicans, CaCdc5p,
and demonstrated that shutting off gene expression under yeast growth
conditions resulted in an early block in nuclear division, followed by
the formation of hyphal-like filaments and expression of some hyphal-specific factors. We currently demonstrate that filament formation in
response to depletion of CaCdc5p is associated with a block in the early
stages of spindle elongation. CaCdc5p localizes to the spindle pole
bodies and spindle, consistent with a role in spindle formation.
Hydroxyurea treatment results in a similar block in spindle elongation
and a corresponding induction of hyphal-like filaments under yeast
growth conditions, supporting the link between spindle elongation and
filament formation. Transcript profiles of the CaCdc5p-depleted and
hydroxyurea-treated filaments demonstrate high similarity to those of
serum-induced hyphae. Hydroxyurea-induced filament formation requires
CaCdc35p, but not Efg1p or Cph1p. Together the results support the
existence of a new pathway within the hyphal signaling networks of
Candida albicans, whereby an endogenous, cell cycle-dependent
mechanism can activate hyphal development.
Return to YGM 2002 Home at SGD