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Search Results: 1 - 10 of 32398 matches for " John Schiefelbein "
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Regulation of cell fate determination in plants
Shucai Wang,John Schiefelbein
Frontiers in Plant Science , 2014, DOI: 10.3389/fpls.2014.00368
Abstract:
Desafíos para los investigadores en educación de América Latina (Challenges for Researchers in Education in Latin America)
Ernesto Schiefelbein
Magis International Journal of Research in Education , 2008,
Abstract: ResumenLa baja comprensión de lectura, constatada por la Organización de las Naciones Unidas para la educación, la ciencia y la cultura –UNESCO-, sugiere investigar sus causas; el escaso avance del programa Educación para Todos (Education for All-EFA) aconseja estudiar los determinantes de una calidad aceptable; y la experiencia de los países desarrollados invita a encontrar modalidades confiables para innovar con éxito en educación. Los tres temas exigen experimentar sistemáticamente mejores programas de formación inicial de docentes y evaluar sus impactos en el aprendizaje de sus alumnos. En este artículo se comentan las revisiones recientes de estudios pertinentes, los elementos por investigar y las precauciones para tener en cuenta en cada uno de ellos.AbstractResearch about the causes of poor reading comprehension, as verified by UNESCO, is essential. The slow progress of the Education for All Program (EFA) suggests studying the determinants of acceptable quality. The experience of developed countries invites the finding of trustable modalities for innovation with success in education. These three subjects imply experimenting systematically with better training programs for teachers and evaluating their impact on student learning. The article discusses recent reviews of pertinent studies, the elements to research, and the precautions to take in consideration with each of them.ResumoA baixa compreens o da leitura, constatada pela UNESCO, sugere pesquisar suas causas; o baixo avan o do programa Educa o para Todos (EFA) aconselha estudar os determinantes de uma qualidade aceitável, e a experiência dos países desenvolvidos motiva a encontrar modalidades confiáveis para inovar com êxito na educa o. Os três temas implicam experimentar sistematicamente melhores programas de forma o inicial de docentes e avaliar seus impactos no aprendizagem dos seus alunos. No artigo discute as revis es recentes de estudos pertinentes, os elemntos
A Mutual Support Mechanism through Intercellular Movement of CAPRICE and GLABRA3 Can Pattern the Arabidopsis Root Epidermis
Natasha Saint Savage,Tom Walker,Yana Wieckowski,John Schiefelbein,Liam Dolan,Nicholas A. M. Monk
PLOS Biology , 2012, DOI: 10.1371/journal.pbio.0060235
Abstract: The patterning of the Arabidopsis root epidermis depends on a genetic regulatory network that operates both within and between cells. Genetic studies have identified a number of key components of this network, but a clear picture of the functional logic of the network is lacking. Here, we integrate existing genetic and biochemical data in a mathematical model that allows us to explore both the sufficiency of known network interactions and the extent to which additional assumptions about the model can account for wild-type and mutant data. Our model shows that an existing hypothesis concerning the autoregulation of WEREWOLF does not account fully for the expression patterns of components of the network. We confirm the lack of WEREWOLF autoregulation experimentally in transgenic plants. Rather, our modelling suggests that patterning depends on the movement of the CAPRICE and GLABRA3 transcriptional regulators between epidermal cells. Our combined modelling and experimental studies show that WEREWOLF autoregulation does not contribute to the initial patterning of epidermal cell fates in the Arabidopsis seedling root. In contrast to a patterning mechanism relying on local activation, we propose a mechanism based on lateral inhibition with feedback. The active intercellular movements of proteins that are central to our model underlie a mechanism for pattern formation in planar groups of cells that is centred on the mutual support of two cell fates rather than on local activation and lateral inhibition.
Comprehensive analysis of single-repeat R3 MYB proteins in epidermal cell patterning and their transcriptional regulation in Arabidopsis
Shucai Wang, Leah Hubbard, Ying Chang, Jianjun Guo, John Schiefelbein, Jin-Gui Chen
BMC Plant Biology , 2008, DOI: 10.1186/1471-2229-8-81
Abstract: By analyzing multiple mutant lines, we report here that TCL1 functions redundantly with other single-repeat R3 MYB transcription factors to control both leaf trichome and root hair formation. On the other hand, ETC1 and ETC3 participate in controlling trichome formation on inflorescence stems and pedicles. Further, we discovered that single-repeat R3 MYBs suppress trichome formation on cotyledons and siliques, organs that normally do not bear any trichomes. By using Arabidopsis protoplast transfection assays, we found that all single-repeat R3 MYBs examined interact with GL3, and that GL1 or WER and GL3 or EGL3 are required and sufficient to activate the transcription of TRY, CPC, ETC1 and ETC3, but not TCL1 and ETC2. Furthermore, only ETC1's transcription was greatly reduced in the gl3 egl3 double mutants.Our comprehensive analysis enables us to draw broader conclusions about the role of single-repeat R3 MYB gene family than were possible in the earlier studies, and reveals the genetic basis of organ-specific control of trichome formation. Our findings imply the presence of multiple mechanisms regulating the transcription of single-repeat R3 MYB genes, and provide new insight into the lateral inhibition mechanism that mediates epidermal cell patterning.There are a total of six genes in the Arabidopsis genome that encode a unique subfamily of MYB transcription factors, namely single-repeat R3 MYB transcription factors. These transcription factors, including TRIPTYCHON (TRY) [1,2], CAPRICE (CPC) [3], TRICHOMELESS1 (TCL1) [4], ENHANCER of TRY and CPC 1, 2, and 3 (ETC1, ETC2 and ETC3 (CPL3)) [5-9], are characterized by their short sequence (75–112 amino acids) and consist largely of the single MYB domain (e.g. without other predicted motifs). It is generally believed that these single-repeat R3 MYB transcription factors mediate lateral inhibition during epidermal patterning. In general, these single-repeat R3 MYB transcription factors act as negative regulators for tri
poolMC: Smart pooling of mRNA samples in microarray experiments
Raghunandan M Kainkaryam, Angela Bruex, Anna C Gilbert, John Schiefelbein, Peter J Woolf
BMC Bioinformatics , 2010, DOI: 10.1186/1471-2105-11-299
Abstract: A theoretical framework to perform smart pooling of mRNA samples in microarray experiments was established and the software implementation of the pooling and decoding algorithms was developed in MATLAB. A proof-of-concept smart pooled experiment was performed using validated biological samples on commercially available gene chips. Differential-expression analysis of the smart pooled data was performed and compared against the unpooled control experiment.The theoretical developments and experimental demonstration in this paper provide a useful starting point to investigate smart pooling of mRNA samples in microarray experiments. Although the smart pooled experiment did not compare favorably with the control, the experiment highlighted important conditions for the successful implementation of smart pooling - linearity of measurements, sparsity in data, and large experiment size.Presently, pooling in microarray experiments refers to the act of mixing messenger RNA (mRNA) collected from several biological-replicate samples, before hybridization onto a microarray chip [1-6]. This form of pooling may be used to reduce biological variation, to lower costs by reducing the number of microarray chips used, and to overcome the problem of limited sample availability.In this paper, we describe a different pooling strategy; a smart pooling strategy based on compression algorithms from digital communication theory. The smart pooling strategy is applied to a large number of diverse biological samples, not necessarily biological replicates, which are pooled and tested on several microarray chips based on a pre-specified pooling design. The mathematical properties of smart pooling designs ensure that each sample is tested on multiple chips, but always in pools made up of a different set of samples, such that, data from all the chips taken together capture the same information as the standard one-sample-one-chip approach. Because of the convolution step involved in testing pools of sa
A Mutual Support Mechanism through Intercellular Movement of CAPRICE and GLABRA3 Can Pattern the Arabidopsis Root Epidermis
Natasha Saint Savage,Tom Walker,Yana Wieckowski,John Schiefelbein,Liam Dolan,Nicholas A. M Monk
PLOS Biology , 2008, DOI: 10.1371/journal.pbio.0060235
Abstract: The patterning of the Arabidopsis root epidermis depends on a genetic regulatory network that operates both within and between cells. Genetic studies have identified a number of key components of this network, but a clear picture of the functional logic of the network is lacking. Here, we integrate existing genetic and biochemical data in a mathematical model that allows us to explore both the sufficiency of known network interactions and the extent to which additional assumptions about the model can account for wild-type and mutant data. Our model shows that an existing hypothesis concerning the autoregulation of WEREWOLF does not account fully for the expression patterns of components of the network. We confirm the lack of WEREWOLF autoregulation experimentally in transgenic plants. Rather, our modelling suggests that patterning depends on the movement of the CAPRICE and GLABRA3 transcriptional regulators between epidermal cells. Our combined modelling and experimental studies show that WEREWOLF autoregulation does not contribute to the initial patterning of epidermal cell fates in the Arabidopsis seedling root. In contrast to a patterning mechanism relying on local activation, we propose a mechanism based on lateral inhibition with feedback. The active intercellular movements of proteins that are central to our model underlie a mechanism for pattern formation in planar groups of cells that is centred on the mutual support of two cell fates rather than on local activation and lateral inhibition.
ANáLISIS DE LOS MODELOS EXPLICATIVOS DE RETENCIóN DE ESTUDIANTES EN LA UNIVERSIDAD: UNA VISIóN DESDE LA DESIGUALDAD SOCIAL
Donoso,Sebastián; Schiefelbein,Ernesto;
Estudios pedagógicos (Valdivia) , 2007, DOI: 10.4067/S0718-07052007000100001
Abstract: the article analyzes the evolution of the studies from the thematic of desertion of students in the universities in chile. the studies on educative results have given to account of a meaning problem associate to poverty. this discussion is in the thematic wich social and educational exclusion is inserted, including the superior level. it debates the main directions on this matter from the indicated theoretical perspective
ANáLISIS DE LOS MODELOS EXPLICATIVOS DE RETENCIóN DE ESTUDIANTES EN LA UNIVERSIDAD: UNA VISIóN DESDE LA DESIGUALDAD SOCIAL Analysis of explicative models of student’s retention at the University: A vision from the social inequality
Sebastián Donoso,Ernesto Schiefelbein
Estudios Pedagógicos (Valdivia) , 2007,
Abstract: El artículo analiza la evolución de los estudios desde la temática de la deserción a la retención de estudiantes en las universidades, contextualizando este fenómeno en el caso chileno, donde los estudios sobre resultados educativos han dado cuenta de un problema de significación asociado a la pobreza. Se inserta esta discusión en la temática de la exclusión social y educativa que genera el sistema educativo, incluyendo el nivel superior, y debate las principales orientaciones sobre esta materia desde la perspectiva teórica se alada The article analyzes the evolution of the studies from the thematic of desertion of students in the universities in Chile. The studies on educative results have given to account of a meaning problem associate to poverty. This discussion is in the thematic wich social and educational exclusion is inserted, including the superior level. It debates the main directions on this matter from the indicated theoretical perspective
A Gene Regulatory Network for Root Epidermis Cell Differentiation in Arabidopsis
Angela Bruex,Raghunandan M. Kainkaryam,Yana Wieckowski,Yeon Hee Kang,Christine Bernhardt,Yang Xia,Xiaohua Zheng,Jean Y. Wang,Myeong Min Lee,Philip Benfey,Peter J. Woolf,John Schiefelbein
PLOS Genetics , 2012, DOI: 10.1371/journal.pgen.1002446
Abstract: The root epidermis of Arabidopsis provides an exceptional model for studying the molecular basis of cell fate and differentiation. To obtain a systems-level view of root epidermal cell differentiation, we used a genome-wide transcriptome approach to define and organize a large set of genes into a transcriptional regulatory network. Using cell fate mutants that produce only one of the two epidermal cell types, together with fluorescence-activated cell-sorting to preferentially analyze the root epidermis transcriptome, we identified 1,582 genes differentially expressed in the root-hair or non-hair cell types, including a set of 208 “core” root epidermal genes. The organization of the core genes into a network was accomplished by using 17 distinct root epidermis mutants and 2 hormone treatments to perturb the system and assess the effects on each gene's transcript accumulation. In addition, temporal gene expression information from a developmental time series dataset and predicted gene associations derived from a Bayesian modeling approach were used to aid the positioning of genes within the network. Further, a detailed functional analysis of likely bHLH regulatory genes within the network, including MYC1, bHLH54, bHLH66, and bHLH82, showed that three distinct subfamilies of bHLH proteins participate in root epidermis development in a stage-specific manner. The integration of genetic, genomic, and computational analyses provides a new view of the composition, architecture, and logic of the root epidermal transcriptional network, and it demonstrates the utility of a comprehensive systems approach for dissecting a complex regulatory network.
Las Creencias de los profesores rurales: una tarea pendiente para la investigación educativa
Vera Bachmann,Daniela; Osses,Sonia; Schiefelbein Fuenzalida,Ernesto;
Estudios pedagógicos (Valdivia) , 2012, DOI: 10.4067/S0718-07052012000100018
Abstract: research on the beliefs in the teaching-learning process has recently become a great issue due to the increasing evidence that points out that it has a great impact in the teacher's pedagogical activities. nevertheless, it has become evident that research on this matter has been focused mainly on the educative system performed in urban areas, on basic and high school levels and higher education, underestimating what occurs in rural areas of our country, field that historically has shown the lowest academic performance. this article presents a view that allows making hypothesis, from the study of the beliefs, of the possible personal variables of the teacher that could explain the results of the learning process shown in the rural education of our country. as conclusion, it is necessary to do research on the rural teacher's beliefs, from the educational perspective, because of the direct consequences on the learning process of the students.
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