Abstract
Mating-type genes control the entry into the sexual cycle, mating identity and sexual development in fungi. The mat A-2 and mat A-3 genes, present in the mat A idiomorph of the filamentous fungus Neurospora crassa, are required for post-fertilization functions but are not essential for mating identity. Their putative roles as transcription factors are based on the similarity of mat A-2 with the Podospora anserina SMR1 gene and an HMG motif present in the mat A-3 gene. In this work the yeast two-hybrid system was used to identify transcriptional activity and protein-protein interaction of N. crassamat A-2 and mat A-3 genes. We observed that the mat A-3 protein alone is capable of weakly activating transcription of yeast reporter genes; it also binds with low specificity to the GAL1 promoter sequence, possibly due to its HMG domain. Our results also indicate that mat A-3 is capable to form homodimers, and interact with mat A-2. Interference on yeast growth was observed on some transformants suggesting a toxic action of the mat A-2 protein. Our data on pattern of interactions of mat proteins contributes towards understanding the control of vegetative and sexual cycles in filamentous fungi.
Highlights
Entry into the sexual cycle in fungi is controlled by the mating-type genes which are responsible for sexual development and identity in filamentous fungi and yeast
It is known that many mat gene products are transcription factors, very little is known about how MAT proteins interact and what are the target genes in filamentous ascomycete fungi
Potential transcriptional activation or silencing of a gene can be detected in yeast reporter gene systems when they are fused to the GAL4 DNA-binding domain (Fields and Song, 1989)
Summary
Entry into the sexual cycle in fungi is controlled by the mating-type (mat) genes which are responsible for sexual development and identity in filamentous fungi and yeast (reviewed in Kronstad and Staben, 1997; Souza et al, 2003). N. crassa mat A-2 and mat A-3 gene products are thought to be transcription factors (Ferreira et al, 1996) and since their description, biochemical data such as those from DNA binding assays have not been reported.
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