Characterization of Cryptococcus neoformans BUD16 homologue
Date Issued
2008
Date
2008
Author(s)
Yeh, Yu-Ling
Abstract
Light regulates the physiology, development and behavior of many organisms including fungi. Cryptococcus neoformans, a heterothallic basidiomycetous yeast, can sense blue light and negatively regulate the production of sexual filaments via the Cwc1 and Cwc2 proteins. To dissect this pathway, we conducted a suppressor screen utilized Agrobacterium tumefaciens-mediated transformation (ATMT) technique to identify mutants suppressing the mating phenotype of the CWC1 overexpression strain, which displayed no filaments under light illumination. Here, we report that the EG30 suppressor strain restored the filamentation to the wild-type level and T-DNA was confirmed to insert at the promoter of a gene homologous to the Saccharomyces cerevisiae BUD16. S. cerevisiae BUD16 gene was identified due to the random budding pattern in the homozygous diploid mutant. The Bud16p protein is a predicted pyridoxal kinase which converts pyridoxal into pyridoxal 5’-phosphate (PLP), the biologically active form of vitamin B6. In C. neoformans, overexpression of the BUD16 gene slightly reduced and delayed the production of dikaryotic filaments when compared to the wild-type strain. Meanwhile, we also found that the bud16 mutants produced mating filaments earlier and more than the wild-type strain and higher cell fusion efficiencies were also verified. On the other hand, monokaryotic filamentation, another sexual process involved the same sex of the MATα cells, appeared unaffected in the MATα bud16 mutants; however, overexpression of the BUD16 gene blocked this differentiation. In epistasis analysis, we found that the mating phenotype of the bud16 mutant under CWC1 overexpression background was similar to the bud16 mutant; while the phenotype of cwc1 gene deletion under the BUD16 overexpression strain was resemble to the BUD16 overexpression strain. These results suggested that BUD16 may be a negative regulator functioning downstream of the Cwc complex during the light-regulated sexual differentiation process.
Subjects
Cryptococcus neoformans
blue light photoresponse
Agrobacterium tumefaciens-mediated transformation
pyridoxal kinase
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