The abaA homologue of Penicillium marneffei participates in two developmental programmes: conidiation and dimorphic growth

Abstract

Penicillium marneffei is the only known species of its genus that is dimorphic. At 25°C, P. marneffei exhibits true filamentous growth and undergoes asexual development producing spores borne on complex structures called conidiophores. At 37°C, P. marneffei undergoes a dimorphic transition to produce uninucleate yeast cells that divide by fission. We have cloned a homologue of the Aspergillus nidulans abaA gene encoding an ATTS/TEA DNA‐binding domain transcriptional regulator and shown that it is involved in both these developmental programs. Targeted deletion of abaA blocks asexual development at 25°C before spore production, resulting in aberrant conidiophores with reiterated terminal cells. At 37°C, the abaA deletion strain fails to switch correctly from multinucleate filamentous to uninucleate yeast cells. Both the transitional hyphal cells, which produce the yeast cells, and the yeast cells themselves contain multiple nuclei. Expression of the abaA gene is activated during both conidiation and the hyphal–yeast switch. Interestingly, the abaA gene of the filamentous monomorphic fungus A. nidulans can complement both conidiation and dimorphic switching defects in the P. marneffei abaA mutant. In addition, ectopic overexpression of abaA results in anucleate yeast cells and multinucleate vegetative filamentous cells. These data suggest that abaA regulates cell cycle events and morphogenesis in two distinct developmental programmes.

Differentially expressed proteins of pathogenic Penicillium marneffei in yeast and mycelial phases

“…Whilst several genes of this fungus, including brlA, abaA and tupA, are thought to be involved in asexual development, fungal morphogenesis and immunogenicity, the mechanisms that regulate the dimorphic switch remain obscure (Borneman et al, 2000(Borneman et al, , 2001Todd et al, 2003). To understand further the significance of P. marneffei dimorphism, we compared the proteomic profiles of P. marneffei at both end points of the dimorphic transition.…”

“…It has long been believed that the phase transition from mycelia to yeast is key to the pathogenicity, but the mechanism that regulates the switch remains unknown (Leberer et al, 1997;Rooney et al, 2001;Sebghati et al, 2000). Borneman et al (2000) found that two genes that showed homology to the brlA and abaA genes were required for the asexual development of P. marneffei. The stlA gene has also been shown to be important for the dimorphic switch of a variety of fungi, but has no detectable effect on vegetative growth, asexual development or dimorphic switching in P. marneffei (Borneman et al, 2001).…”

Control of morphogenesis and actin localization by thePenicillium marneffei RAChomolog

“…Genomic DNA from P. marneffei and A. nidulans was isolated as previously described (Borneman et al, 2001). RNA was prepared using the FastRNA kit from Bio101 as previously described (Borneman et al, 2000). RNA was isolated from vegetative hyphal cells grown at 25°C for 2 days in liquid medium, from asexually developing cultures grown on solid medium at 25°C for 4 days and from yeast cells grown at 37°C for 8 days in liquid medium.…”

“…Database searches and sequence comparison were performed using the Australian National Genomic Information Service. A cDNA library, constructed using the SMART cDNA Library construction kit (Clontech Laboratories) with RNA isolated from a 37°C vegetative culture (Borneman et al, 2000) was probed with a 2.5 kb SpeI/EcoRI fragment of cflB (50% formamide, 0.1× SSC, 37°C).…”

“…At 37°C, strains were grown on either brain-heart infusion (BHI) or synthetic dextrose (SD) medium. The gpdA(p)::gfp::cflB strains were grown in liquid SD medium at 37°C (Ausubel et al, 1994 Microscopy P. marneffei strains were grown on slides covered with a thin layer of solid medium and with one end resting in liquid medium (Borneman et al, 2000).…”