161 research outputs found
Budding yeast as a model organism to study the effects of age
Although a budding yeast culture can be propagated eternally, individual yeast cells age and eventually die. The detailed knowledge of this unicellular eukaryotic species as well as the powerful tools developed to study its physiology makes budding yeast an ideal model organism to study the mechanisms involved in aging. Considering both detrimental and positive aspects of age, we review changes occurring during aging both at the whole-cell level and at the intracellular level. The possible mechanisms allowing old cells to produce rejuvenated progeny are described in terms of accumulation and inheritance of aging factors. Based on the dynamic changes associated with age, we distinguish different stages of age: early age, during which changes do not impair cell growth; intermediate age, during which aging factors start to accumulate; and late age, which corresponds to the last divisions before death. For each aging factor, we examine its asymmetric segregation and whether it plays a causal role in aging. Using the example of caloric restriction, we describe how the aging process can be modulated at different levels and how changes in different organelles might interplay with each other. Finally, we discuss the beneficial aspects that might be associated with ag
Spindle orientation in Saccharomyces cerevisiae depends on the transport of microtubule ends along polarized actin cables
Microtubules and actin filaments interact and cooperate in many processes in eukaryotic cells, but the functional implications of such interactions are not well understood. In the yeast Saccharomyces cerevisiae, both cytoplasmic microtubules and actin filaments are needed for spindle orientation. In addition, this process requires the type V myosin protein Myo2, the microtubule endâbinding protein Bim1, and Kar9. Here, we show that fusing Bim1 to the tail of the Myo2 is sufficient to orient spindles in the absence of Kar9, suggesting that the role of Kar9 is to link Myo2 to Bim1. In addition, we show that Myo2 localizes to the plus ends of cytoplasmic microtubules, and that the rate of movement of these cytoplasmic microtubules to the bud neck depends on the intrinsic velocity of Myo2 along actin filaments. These results support a model for spindle orientation in which a Myo2âKar9âBim1 complex transports microtubule ends along polarized actin cables. We also present data suggesting that a similar process plays a role in orienting cytoplasmic microtubules in mating yeast cells
Influence du pastoralisme sur les populations acridiennes dans le massif du Siroua (Maroc)
Un foyer de grĂ©garisation de #Dociostaurus maroccanus (Thunb.) a Ă©tĂ© Ă©tudiĂ© au cours de cinq missions annuelles (1988-1993). Le site d'Ă©tude est un pĂąturage d'altitude dans l'Anti-Atlas (2300 m) oĂč les troupeaux estivent. Sur les 2850 ha de pĂąturages Ă #Poa bulbosa le nombre de moutons et de chĂšvres a Ă©tĂ© estimĂ© Ă 7200 tĂȘtes (une tĂȘte pour 0,4 ha). Les acridiens (18 espĂšces) et leurs prĂ©dateurs (14 espĂšces d'insectes et oiseaux) sont cantonnĂ©s autour d'une prairie de fauche et des cultures irriguĂ©es (55 ha). Le site de ponte du criquet marocain est sur un parc Ă moutons de 2 hectares. La densitĂ© moyenne d'oothĂšques est de 77/m2, dont 37 % sont dĂ©truites par des larves de colĂ©optĂšres (mĂ©loĂŻdes) et des larves de diptĂšres. #Falco naumanni Fleicher et #Pyrrhocorax pyrrhocorax docilis Gm. sont les prĂ©dateurs de criquets, importants sur le site. Les craves Ă bec rouge ont Ă©tĂ© observĂ©s dĂ©terrant les oothĂšques pour les manger. Il est connu que les moutons crĂ©ent les conditions favorables Ă la grĂ©garisation du criquet marocain. Nous montrons que le strict calendrier des activitĂ©s pastorales influence aussi la dynamique des populations acridiennes : les Ă©closions ont lieu en mai dans un milieu non perturbĂ© par les moutons et Ă l'abri des prĂ©dateurs jusqu'Ă la fenaison. La transhumance le 28 juillet, en pleine saison de ponte, modifie l'espace et les ressources trophiques disponibles. (RĂ©sumĂ© d'auteur
Particle-based model of cellular morphogenesis in budding yeast
We apply Lagrangian particle method combined with the level-set method to model morphogenesis of budding yeast on the subcellular level. We model the biochemical reactions, anisotropic diffusion, membrane-cytoplasmic transport of proteins and introduction of new membrane material (exocytosis) that occur on the plasma membrane. Exocytosis results in protrusion of the membrane surface. Hence, to model these phenomena we need to solve a system of reaction-diffusion-advection equations on the evolving surface
The evolutionary conserved BER1 gene is involved in microtubule stability in yeast
In yeast, microtubules are dynamic filaments necessary for spindle and nucleus positioning, as well as for proper chromosome segregation. We identify a function for the yeast gene BER1 (Benomyl REsistant 1) in microtubule stability. BER1 belongs to an evolutionary conserved gene family whose founding member Sensitivity to Red light Reduced is involved in red-light perception and circadian rhythms in Arabidopsis. Here, we present data showing that the ber1Î mutant is affected in microtubule stability, particularly in presence of microtubule-depolymerising drugs. The pattern of synthetic lethal interactions obtained with the ber1Î mutant suggests that Ber1 may function in N-terminal protein acetylation. Our work thus suggests that microtubule stability might be regulated through this post-translational modification on yet-to-be determined protein
Septin-dependent compartmentalization of the endoplasmic reticulum during yeast polarized growth
Polarized cells frequently use diffusion barriers to separate plasma membrane domains. It is unknown whether diffusion barriers also compartmentalize intracellular organelles. We used photobleaching techniques to characterize protein diffusion in the yeast endoplasmic reticulum (ER). Although a soluble protein diffused rapidly throughout the ER lumen, diffusion of ER membrane proteins was restricted at the bud neck. Ultrastructural studies and fluorescence microscopy revealed the presence of a ring of smooth ER at the bud neck. This ER domain and the restriction of diffusion for ER membrane proteins through the bud neck depended on septin function. The membrane-associated protein Bud6 localized to the bud neck in a septin-dependent manner and was required to restrict the diffusion of ER membrane proteins. Our results indicate that Bud6 acts downstream of septins to assemble a fence in the ER membrane at the bud neck. Thus, in polarized yeast cells, diffusion barriers compartmentalize the ER and the plasma membrane along parallel lines
La dinĂĄmica de los estados de fosforilaciĂłn de las vĂas HOG y de las feromonas en levaduras
Comunicaciones a congreso
Annotating novel genes by integrating synthetic lethals and genomic information
<p>Abstract</p> <p>Background</p> <p>Large scale screening for synthetic lethality serves as a common tool in yeast genetics to systematically search for genes that play a role in specific biological processes. Often the amounts of data resulting from a single large scale screen far exceed the capacities of experimental characterization of every identified target. Thus, there is need for computational tools that select promising candidate genes in order to reduce the number of follow-up experiments to a manageable size.</p> <p>Results</p> <p>We analyze synthetic lethality data for <it>arp1 </it>and <it>jnm1</it>, two spindle migration genes, in order to identify novel members in this process. To this end, we use an unsupervised statistical method that integrates additional information from biological data sources, such as gene expression, phenotypic profiling, RNA degradation and sequence similarity. Different from existing methods that require large amounts of synthetic lethal data, our method merely relies on synthetic lethality information from two single screens. Using a Multivariate Gaussian Mixture Model, we determine the best subset of features that assign the target genes to two groups. The approach identifies a small group of genes as candidates involved in spindle migration. Experimental testing confirms the majority of our candidates and we present <it>she1 </it>(YBL031W) as a novel gene involved in spindle migration. We applied the statistical methodology also to TOR2 signaling as another example.</p> <p>Conclusion</p> <p>We demonstrate the general use of Multivariate Gaussian Mixture Modeling for selecting candidate genes for experimental characterization from synthetic lethality data sets. For the given example, integration of different data sources contributes to the identification of genetic interaction partners of <it>arp1 </it>and <it>jnm1 </it>that play a role in the same biological process.</p
Las peliculas de Jean-Pierre Melville
Montmayeur, Y.; Casas, Q.; Angulo, J.; Barral, MĂ.; Aguilar, C. (1993). Las peliculas de Jean-Pierre Melville. Nosferatu. Revista de cine. (13):80-105. http://hdl.handle.net/10251/40878.ImportaciĂłn Masiva801051
Tracking and synchronization of the yeast cell cycle using dielectrophoretic opacity
Cell cycle synchronization is an important tool for the study of the cell division stages and signalling. It provides homogeneous cell cultures that are of importance to develop and improve processes such as protein synthesis and drug screening. The main approach today is the use of metabolic agents that block the cell cycle at a particular phase and accumulate cells at this phase, disturbing the cell physiology. We provide here a non-invasive and label-free continuous cell sorting technique to analyze and synchronize yeast cell division. By balancing opposing dielectrophoretic forces at multiple frequencies, we maximize sensitivity to the characteristic shape and internal structure changes occurring during the yeast cell cycle, allowing us to synchronize the culture in late anaphase
- âŠ