Regulation of membrane fatty acid composition by temperature in mutants of Arabidopsis with alterations in membrane lipid composition

BACKGROUND: A wide range of cellular responses occur when plants are exposed to elevated temperature, including adjustments in the unsaturation level of membrane fatty acids. Although membrane bound desaturase enzymes mediate these adjustments, it is unknown how they are regulated to achieve these specific membrane compositions. Furthermore, the precise roles that different membrane fatty acid compositions play in photosynthesis are only beginning to be understood. To explore the regulation of the membrane composition and photosynthetic function in response to temperature, we examined the effect of temperature in a collection of mutants with altered membrane lipid fatty acid composition. RESULTS: In agreement with previous studies in other species, the level of unsaturation of membrane fatty acids in Arabidopsis was inversely correlated with growth temperature. The time required for the membrane fatty acids to attain the composition observed at elevated temperature was consistent with the timing required for the synthesis of new fatty acids. Comparisons of temperature-induced fatty acid alterations in membranes were made among several Arabidopsis lines including wild-type Columbia, and the compositional mutants, fad5, fad6, act1 and double mutants, fad7 fad8 and act1 fad6. The results revealed key changes that occur in response to elevated temperature regardless of the specific mutations in the glycerolipid pathway, including marked decreases in trienoic fatty acids and consistent increases in unsaturated 16:0 and in dienoic 18:2 levels. Fluorescence measurements of various mutants indicated that photosynthetic stability as well as whole plant growth at elevated temperature is influenced by certain membrane fatty acid compositions. CONCLUSIONS: The results of this study support the premise that defined proportions of saturated and unsaturated fatty acids in membrane lipids are required for photosynthetic thermostability and acclimation to elevated temperature. The results also suggest that changes in the membrane fatty acid composition brought about in response to temperature are regulated in such a way so as to achieve highly similar unsaturation levels despite mutations that alter the membrane composition prior to a high-temperature exposure. The results from examination of the mutant lines also suggest that interorganellar transfer of fatty acids are involved in mediating temperature-induced membrane alterations, and reveal steps in the fatty acid unsaturation pathway that appear to have key roles in the acclimatization of membranes to high temperature

Tumor Formation in Response to Loss of Chromatin Remodeler Chd5 in Zebrafish

Chromodomain helicase DNA binding protein 5 (CHD5) has been identified as a tumor suppressor in humans. Deletion or mutation of CHD5 has been observed in numerous cancers, including neuroblastoma and melanoma. We hypothesize that chd5 is also a tumor suppressor in zebrafish, a powerful model system to study tumorigenesis. Many genes involved in tumorigenesis are conserved in zebrafish, and they develop fully penetrant tumor phenotypes. We have created chd5 knock-out zebrafish using CRISPR/Cas9 and are monitoring them for tumor development. In addition to the chd5 knock-outs, we are undertaking a double-mutant approach by coupling loss of chd5 with other genes known to be important for tumor formation. Specifically, we are using a mutant form of the oncogene BRAF-V600E and a mutant version of the tumor suppressor tp53. BRAF-V600E is a kinase that promotes cell division. Tp53 is tumor suppressor gene that initiates apoptosis when severe DNA damage occurs. Expression of gain-of-function BRAF-V600E gene creates nevi in zebrafish, similar to the production of moles in humans, but is not sufficient to promote melanoma formation. Tp53 when mutated results in nerve sheath tumors in zebrafish at 8.5 months. When BRAF-V600E mutant is combined with mutant tp53, the fish develop melanomas beginning at 4 months. We have crossed our chd5 knock-out alleles with BRAF-V600E and tp53 to create various mutant lines, and we are examining the resulting progeny for tumor development, specifically melanoma. Establishment of a chd5-dependent tumor model using zebrafish will enable novel studies of the function of CHD5 in human cancers

Using the INTACT method to study PICKLE in individual cell types

Cell differentiation is an essential part of development in multicellular organisms. Cells with identical genomic DNA are able to differentiate into a variety of tissues due to selective expression and repression of genes. This tissue-specific gene expression is enabled in part by proteins called chromatin remodelers, which can move, remove, or restructure histone proteins to restrict or allow physical access to genomic DNA. PICKLE (PKL) is a member of the CHD family of ATP-dependent chromatin remodelers that promotes cellular identity in the plant model organism Arabidopsis thaliana. PKL promotes cell identity by silencing embryonic genes during seed germination by promoting the repressive epigenetic modification trimethylation of lysine 27 on histone H3 (H3K27me3). However, the contributions of PKL to H3K27me3 and gene expression have only been studied on an organism-wide scale. Due to the wide variety of tissues that comprise a plant, the specific role of PKL in a given cell type cannot be determined by examining levels of gene expression and epigenetic modifications as averaged across the organism. Through use of the INTACT (isolating nuclei tagged in specific cell types) method, nuclei of two different cell types will be tagged and purified from both wild-type Arabidopsis and Arabidopsis lacking functional PKL. Isolating nuclei from one cell type at a time will allow us to study the function of PKL at a much higher resolution. This will provide both a better understanding of PKL function and a precedent for studies of how CHD chromatin remodelers regulate gene expression in other organisms

Intervenciones Psicosociales en las Inundaciones de Sierras Chicas

En el marco de las Prácticas Profesionales en Servicio de la Facultad de Psicología, UNC, en las localidades afectadas por las inundaciones de Sierras Chicas: Mendiolaza, Río Ceballos y Unquillo, se presentan las intervenciones desarrolladas durante el 2015. Se trabajó a partir de la perspectiva de gestión psicosocial de riesgo, realizando asistencia clínica y trabajo en comunidad. Acompañar a las comunidades en su proceso de rehabilitación psicosocial, en conjunto con los equipos de salud locales. Investigación Acción Participativa. Se logró acompañar y asistir a los damnificados de las inundaciones. Se promovió la articulación de redes entre las comunidades y entre las comunidades y las instituciones. Se reforzó el trabajo de los equipos locales de salud en la asistencia de los damnificados. Se promovió el fortalecimiento de la participación activa en la toma de decisiones y autogestión de los vecinos. Considerando la complejidad de trabajar con comunidades vulnerabilizadas por diversos factores sumado al fuerte impacto del evento y a la desestructuración-irrupción del tejido social, es importante discutir la construcción del rol del psicólogo en esta área emergente. En este sentido se entiende que uno de los aspectos fundamentales a tener en cuenta es el trabajo interdisciplinario y la articulación intersectorial. Finalmente se resalta la necesidad de la continuidad del equipo de trabajo para pensar y proponer nuevas estrategias y líneas de acción preventivas, de capacitación, y de promoción de la salud integral

Yeast IME2 Functions Early in Meiosis Upstream of Cell Cycle-Regulated SBF and MBF Targets

BACKGROUND: In Saccharomyces cerevisiae, the G1 cyclin/cyclin-dependent kinase (CDK) complexes Cln1,-2,-3/Cdk1 promote S phase entry during the mitotic cell cycle but do not function during meiosis. It has been proposed that the meiosis-specific protein kinase Ime2, which is required for normal timing of pre-meiotic DNA replication, is equivalent to Cln1,-2/Cdk1. These two CDK complexes directly catalyze phosphorylation of the B-type cyclin/CDK inhibitor Sic1 during the cell cycle to enable its destruction. As a result, Clb5,-6/Cdk1 become activated and facilitate initiation of DNA replication. While Ime2 is required for Sic1 destruction during meiosis, evidence now suggests that Ime2 does not directly catalyze Sic1 phosphorylation to target it for destabilization as Cln1,-2/Cdk1 do during the cell cycle. METHODOLOGY/PRINCIPAL FINDINGS: We demonstrated that Sic1 is eventually degraded in meiotic cells lacking the IME2 gene (ime2Δ), supporting an indirect role of Ime2 in Sic1 destruction. We further examined global RNA expression comparing wild type and ime2Δ cells. Analysis of these expression data has provided evidence that Ime2 is required early in meiosis for normal transcription of many genes that are also periodically expressed during late G1 of the cell cycle. CONCLUSIONS/SIGNIFICANCE: Our results place Ime2 at a position in the early meiotic pathway that lies upstream of the position occupied by Cln1,-2/Cdk1 in the analogous cell cycle pathway. Thus, Ime2 may functionally resemble Cln3/Cdk1 in promoting S phase entry, or it could play a role even further upstream in the corresponding meiotic cascade

Gene coexpression clusters and putative regulatory elements underlying seed storage reserve accumulation in Arabidopsis

Abstract Background In Arabidopsis, a large number of genes involved in the accumulation of seed storage reserves during seed development have been characterized, but the relationship of gene expression and regulation underlying this physiological process remains poorly understood. A more holistic view of this molecular interplay will help in the further study of the regulatory mechanisms controlling seed storage compound accumulation. Results We identified gene coexpression networks in the transcriptome of developing Arabidopsis (Arabidopsis thaliana) seeds from the globular to mature embryo stages by analyzing publicly accessible microarray datasets. Genes encoding the known enzymes in the fatty acid biosynthesis pathway were found in one coexpression subnetwork (or cluster), while genes encoding oleosins and seed storage proteins were identified in another subnetwork with a distinct expression profile. In the triacylglycerol assembly pathway, only the genes encoding diacylglycerol acyltransferase 1 (DGAT1) and a putative cytosolic "type 3" DGAT exhibited a similar expression pattern with genes encoding oleosins. We also detected a large number of putative cis-acting regulatory elements in the promoter regions of these genes, and promoter motifs for LEC1 (LEAFY COTYLEDON 1), DOF (DNA-binding-with-One-Finger), GATA, and MYB transcription factors (TF), as well as SORLIP5 (Sequences Over-Represented in Light-Induced Promoters 5), are overrepresented in the promoter regions of fatty acid biosynthetic genes. The conserved CCAAT motifs for B3-domain TFs and binding sites for bZIP (basic-leucine zipper) TFs are enriched in the promoters of genes encoding oleosins and seed storage proteins. Conclusions Genes involved in the accumulation of seed storage reserves are expressed in distinct patterns and regulated by different TFs. The gene coexpression clusters and putative regulatory elements presented here provide a useful resource for further experimental characterization of protein interactions and regulatory networks in this process.</p

Con el ojo en el microscopio parte III

Introducción: La importancia de este proyecto radica en acercar la Universidad a la comunidad, para no solo cumplimentar con objetivos referidos a la prevención y promoción de la salud, sino que, además, acerca la ciencia a los niños y adolescentes de los sectores más carenciados, quienes no tienen definido su futuro, y piensan y ven muy lejano el ámbito universitario. En cuanto a prevención de enfermedades bucodentales no solo se abordaron temas como caries y enfermedad periodontal ( patologías más comunes), sino que además profundizamos en cómo estas patologías pueden afectar en la práctica deportiva y disminuye la Salud Integral de los individuos. Para estas actividades se implementó el uso de microscopios ópticos y digitales. Esto además de generar un entusiasmo particular por el conocimiento y la ciencia, sirvió para la detección temprana y diagnóstico oportuno y el desarrollo posterior de actividades preventivas específicas. Al llevarse a cabo con alumnos de los primeros años de la carrera de Odontología, también se busca generar un perfil del egresado socio-culturalmente comprometido con la comunidad, donde docentes y alumnos generen un ámbito distendido de trabajo que favorezca la educación no formal y el aprender haciendo.Facultad de Odontologí

Modificaciones en la microdureza superficial del esmalte con bhs sometido a la accion de una bebida saborizada

En este trabajo se busca determinar la variación que sufre la microdureza de la superficie del esmalte, con bandas de Hunter Schreger (BHS), a nivel del límite amelodentinario, antes y después de ser sumergidas en 100 ml de agua saborizada durante 12 minutos. Se utilizaron muestras de cortes en sentido vestíbulo-lingual de coronas dentales, incluidas en resina acrílica, desgastadas con papel de lija de distinta granulometría de manera decreciente, pulidas a brillo espejo, lavadas con ultrasonido y secadas con calor seco.Facultad de Odontologí