TUP1 disruption reveals biological differences between MATa and MATα strains of Cryptococcus neoformans

Abstract

SummaryCryptococcus neoformans exists in two mating types MATa and MAT a a a a . Although the morphology, growth characteristics and genetic segregation patterns among MATa and MAT a a a a strains are indistinguishable in the laboratory, the predominance of MAT a a a a strains in nature suggests that MAT a a a a strains are better suited for survival in nature. We disrupted the TUP1 gene, a global repressor, to find the possible biological differences in congenic MAT a a a a and MATa cells of C. neoformans. Disruption of TUP1 affected neither the yeast nor the hyphal cell morphology but resulted in a similar reduction of mating frequencies in both MAT a a a a and MATa cells. Disruption of TUP1 , however, functionally manifested itself in several mating type-dependent phenotypes: (i) MAT a a a a cells became more sensitive to 0.8 M KCl while MATa cells showed no change in sensitivity, (ii) a temperature-dependent growth reduction was exhibited at both 30 ∞ ∞ ∞ ∞ C and 25 ∞ ∞ ∞ ∞ C in MATa but a similar growth reduction was not observed in MAT a a a a cells until the temperature was lowered to 25 ∞ ∞ ∞ ∞ C and (iii) the transcriptional level of genes in several different biological pathways was markedly altered in a mating type-dependent manner. This work is the first case in which non-mating-related biological differences are observed between two congenic mating partners in yeast.

Molecular cloning and characterization of WdTUP1, a gene that encodes a potential transcriptional repressor important for yeast-hyphal transitions in Wangiella (Exophiala) dermatitidis

“…For example, the WdTUP1 disruption mutant showed increased sensitivity to 0.8 M KCl compared with the wild-type W. dermatitidis (data not shown), which suggested that WdTUP1 plays a role in a stress response pathway in a manner similar of that reported with C. neoformans (Lee et al, 2005). Despite its potential role in many processes, we decided during this study to focus on investigating the specific role of WdTup1p in controlling the morphological transitions of its many morphotypes because each may differentially enhance its pathogenicity.…”

“…It is clear that a plethora of roles are played by Tup1p transcription factors in fungi, and both similarities and differences have been shown in terms of the cellular morphogenetic processes they regulate (Lee et al, 2005;Todd et al, 2003). Those roles in turn suggest that although the Tup1p proteins of different fungi have similar protein sequences, functionally they behave very differently.…”

“…Moreover, in Penicillium marneffei, TupA is involved in the repression of both spore and yeast morphogenesis (Todd et al, 2003). Finally, although disruption of TUP1 does not affect the morphology of yeast and hyphal growth in Cryptococcus neoformans, it does reduce the mating frequencies in both MATa and MATα cells, thereby demonstrating its importance to mating type-dependent phenotypes (Lee et al, 2005).…”

Regulatory Diversity ofTUP1inCryptococcus neoformans

“…In Penicillium marneffei, the only dimorphic species known in the genus Penicillium, deletion of the TUP1 homolog, tupA, confers reduced filamentation and abnormality in yeast morphogenesis (38). In the filamentous fungi Aspergillus nidulans and Neurospora crassa, deletion of the TUP1 homologs, rcoA and rco-1, respectively, severely affects growth and sexual and asexual reproduction (12,46).Cryptococcus neoformans is a bipolar heterothallic basidiomycetous yeast with two serotypes, A and D, and the function of Tup1 has been studied only for serotype D strains (26,27). While disruption of TUP1 in strains of serotype D did not affect yeast or hyphal cell morphology, it resulted in matingtype-dependent differences, including temperature-dependent growth, sensitivity to 0.8 M KCl, and expression of genes in several other biological pathways (26).…”

TheAspergillus nidulans rcoAGene Is Required forveA-Dependent Sexual Development

“…RCO1 is required for female sexual development (Yamashiro et al 1996) and TUP1 is required for MATa sexual function (Mukai et al 1991). Cryptococcus neoformans TUP1 also functions in mating (Lee et al 2005). Therefore rcoA homologs act as key regulators of sexual development in fungi.…”