RESEARCH INTERESTS

One of the most attractive fields in Biology is the knowledge of how organisms are able to generate and keep a predestined shape. We use yeasts as model organisms to study morphogenesis because they are eukaryotic unicellular organisms. They have the advantage of developing all the morphogenetic processes in one single cell so the relationship between the morphogenetic controls and their effect in the organism can be easily analyzed. There are three morphogenetic events which cells must regulate tightly to guarantee their survival as organisms and, therefore, to ensure the propagation of their species: establishment of polarity, cytokynesis and sexual development.

Our goal is to study the role of exocytosis and endocytosis in the morphogenesis of the fission yeast Schizosaccharomyces pombe. Particularly, we are interested in uncovering the relationship between vesicle transport and cytokinesis, mating, and response to stress. Our particular objectives are:

Role of clathrin and the adaptor complexes in S. pombe morphogenesis. We have cloned clc1+, the gene coding for the clathrin light chain. This gene is essential for viability. At this moment, we are obtaining conditional mutants that will help us to study the role of clathrin in the processes of secretion, endocytosis, and stress response. Additionally, we have cloned apl3+, which codes for the ? subunit of the AP-2 complex. This gene induces during mating and in response to stress so we will study the relationship of this complex with these processes.

Study of exomer proteins. In Saccharomyces cerevisiae the term “EXOMER” refers to a group of proteins that participates in a multiprotein complex required for the secretion of some transmembrane proteins from the Golgi to the plasma membrane. Chs5p is an exomer component required for chitin synthesis and for mating. Chs6p is another exomer protein required for chitin synthesis but not for mating. In S. pombe there is a protein (Cfr1p) with similarity to Chs5p and a protein (Csr1p) with similarity with Chs6p. We are studying the role of these proteins in cell wall synthesis and in mating. Also, we aim to determine whether Cfr1p and Cs1p form a vesicle-coat similar to the S. cerevisiae exomer.

Study of the fungal claudins dni1+, dni2+and sur7+, and the tetraspan prm1+. These genes code for tetraspans (proteins with four transmembrane domains). We have shown that Dni1p and Dni2p are required for membrane organization and cell wall remodelling during sexual cell fusion. These proteins belong to the Sur7- and Fig1-related fungal claudins. Sur7p is involved in endocytosis and cell wall remodelling in S. cerevisiae and C. albicans. We want to analyze the functional relationship between Dni1p, Dni2p and Sur7p. Also, initial results have shown that Prm1p is essential for cell fusion. We will analyze its functional relationship with the fungal claudins. Additionally, we will use these proteins as markers to analyze the role of the exomer and clathrin in the secretion and the endocytosis of this group of proteins during sexual development.