Depletion of a Polo-like Kinase inCandida albicansActivates Cyclase-dependent Hyphal-like Growth

Abstract

Morphogenesis in the fungal pathogen Candida albicans is an important virulence-determining factor, as a dimorphic switch between yeast and hyphal growth forms can increase pathogenesis. We identified CaCDC5, a cell cycle regulatory polo-like kinase (PLK) in C. albicans and demonstrate that shutting off its expression induced cell cycle defects and dramatic changes in morphology. Cells lacking CaCdc5p were blocked early in nuclear division with very short spindles and unseparated chromatin. GFP-tagged CaCdc5p localized to unseparated spindle pole bodies, the spindle, and chromatin, consistent with a role in spindle elongation at an earlier point in the cell cycle than that described for the homologue Cdc5p in yeast. Strikingly, the cell cycle defects were accompanied by the formation of hyphal-like filaments under yeast growth conditions. Filament growth was determinate, as the filaments started to die after 24 h. The filaments resembled serum-induced hyphae with respect to morphology, organization of cytoplasmic microtubules, localization of nuclei, and expression of hyphal-specific components. Filament formation required CaCDC35, but not EFG1 or CPH1. Similar defects in spindle elongation and a corresponding induction of filaments occurred when yeast cells were exposed to hydroxyurea. Because CaCdc5p does not appear to act as a direct repressor of hyphal growth, the data suggest that a target of CaCdc5p function is associated with hyphal-like development. Thus, an internal, cell cycle-related cue can activate hyphal regulatory networks in Candida.

Critical Role of DNA Checkpoints in Mediating Genotoxic-Stress–induced Filamentous Growth inCandida albicans

“…In addition, Wu and Jiang (2005) recently found that a S. cerevisiae mutant expressing cdc42-Y40F was specifically defective in HUinduced filamentous growth and thus proposed a direct interaction between Rad53p and Cdc42p, a Rho GTPase essential for polarized cell growth (Etienne-Manneville, 2004). Moreover, ScRad53p activation is known to lead to G 2 /M arrest by inhibiting the Polo-like kinase Cdc5p (Sanchez et al, 1999), and depletion of CaCdc5p has been shown to cause cell elongation (Bachewich et al, 2003). Further studies of the molecular events linking CaRad53p to cell morphogenesis might well follow these leads from S. cerevisiae.…”

“…These conditions more-or-less mimic certain host conditions. Interestingly, recent experiments have revealed a seemingly new mechanism for induction of filamentous growth that is caused by the perturbation of cell-cycle progression and is, in at least some cases, independent of the cAMP/PKA and MAP-kinase pathways (Bai et al, 2002;Bachewich et al, 2003;Andaluz et al, 2006; AtirLande et al, 2005;Bensen et al, 2005;Chapa y Lazo et al, 2005). An intriguing observation is that interfering with either an early or a late cell-cycle event, or with events thought to activate distinct cell-cycle checkpoints, appears to have strikingly similar effects on cell morphogenesis.…”

“…Similar growth also occurs as the result of switching off the expression of either the G 1 cyclin Cln3p Chapa y Lazo et al, 2005) or one of the mitotic cyclins Clb2p and Clb4p (Bensen et al, 2005). Furthermore, deletion of CDC4, which encodes a component of the ubiquitin ligase SCF Cdc4p and is thought This article was published online ahead of print in MBC in Press (http://www.molbiolcell.org/cgi/doi/10.1091/mbc.E06 -05-0442) on December 20, 2006. to have a role in determining cellular events around the G 1 /S transition, or depleting the polo-like kinase Cdc5p, which is required for mitotic exit, causes constitutive filamentous growth (Bachewich et al, 2003;Atir-Lande et al, 2005). Currently, the signal-transduction pathways that mediate such induction of filamentous growth by cell-cycle perturbations are almost entirely unknown.…”

Dynein-dependent nuclear dynamics affect morphogenesis inCandida albicansby means of the Bub2p spindle checkpoint

“…Thus, fungi employ checkpoints to ensure that nuclei move appropriately with respect to morphology. Unlike S. cerevisiae, activation of the DNA damage (Bedell et al, 1980;Shi et al, 2007) or spindle checkpoints (Bachewich et al, 2003;Bai et al, 2002) does not arrest bud growth in C. albicans; the result is the formation of elongated pseudohyphal-like buds (Berman, 2006). Interestingly, nuclei migrate into these elongated buds before mitosis, with dynamics reminiscent of the migration of nuclei into hyphal germ tubes.…”

Effect of Propranolol on Hyphae Formation Signal in Candida albicans

“…[13][14][15] EFG1 is a transcription factor and EFG1-deficient mutants are unable to form hyphae despite the presence of serum. 16,17) Hyphae-specific proteins such as agglutinin like sequence 3 (ALS3) and ALS8 are cell wall proteins in C. albicans, and the expressions are regulated by EFG1. 18,19) Propranolol is a human b adrenergic receptor blocking agent.…”