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| Author(s): |
Ludimila Dias Almeida
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Campinas, SP. |
| Institution: | Universidade Estadual de Campinas (UNICAMP). Instituto de Biologia |
| Defense date: | 2015-02-26 |
| Examining board members: |
Gonçalo Amarante Guimarães Pereira;
Jorge Mauricio Costa Mondego;
Ronaldo José Durigan Dalio
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| Advisor: | Gonçalo Amarante Guimarães Pereira |
| Abstract | |
The basidiomycetes¿ sexual cycle is controlled by the mating type system. The structure of this system comprises two unlinked multigenic loci, A and B. The A locus codes for homeodomain proteins, HD1 e HD2 which form a heterodimer, and B locus presents pheromone receptors and pheromones. In outcrossing (heterothallic) fungi, sexual development depends on the compatibility of four genes in two different allelic versions in a so-called tetrapolar system, and is strictly activated by specific interactions between different parental alleles, ensuring that genetically identical hyphae are incompatible. The phytopathogen Moniliophthora perniciosa causes Witches¿ broom disease in cacao plants, and it is a typical basidiomycete fungi. However, it completes its sexual development through the crossing of genetically identical hyphae, and is the first described homothallic fungi with a complete tetrapolar genetic system. Here we show the characterization of the mating type loci of M. perniciosa and the transcriptional profile of these genes, to uncover the mechanisms underpinning its homothallic behavior. First, we identified an A locus, a B locus and a set of genes that participates in pheromone processing and signalization. Considering the transcriptional profile of these genes, one receptor shows an expression profile consistent with an involvement in dikaryotization. The functional evaluation of the receptors was performed in a heterologous expression system, a promising tool for GPCR (G coupled proteins receptors) proteins study. This system did not allow the confirmation if M. perniciosa contains compatible alleles for receptors and pheromones, one possible explanation for homothallism. Considering A locus, it codes for a pair MpHD1 and MpHD2, which has a sequence insertion (11,958kb) interrupting their promoters, differing from others basidiomycetes. The hypothesis in this scenario is that the insertion of a transposon could have allowed an unequal crossover that brought together compatible genes in the same allele, causing the homothallism in this species. Interestingly, in an opposite direction, our data indicates that a previous transition for homothallism could have resulted in a relaxed selective pressure on mating type loci, with consequences such as the presence of degenerated genes on these loci. In this context, the mating type genes could not necessarily play a role in dikaryotization process. This work provides valuable data for understanding the sexual biology of M. perniciosa, which hereafter could be correlated with its phytopathogenicity (AU) | |
| FAPESP's process: | 13/05192-5 - Gene transcriptional regulation and molecular basis of Moniliophthora perniciosa homothallic sexual development |
| Grantee: | Ludimila Dias Almeida |
| Support Opportunities: | Scholarships in Brazil - Master |