33 research outputs found
Clathrin mediates endocytosis and polar distribution of PIN auxin transporters in Arabidopsis
No full textEndocytosis is a crucial mechanism by which eukaryotic cells internalize extracellular and plasma membrane material, and it is required for a multitude of cellular and developmental processes in unicellular and multicellular organisms. In animals and yeast, the best characterized pathway for endocytosis depends on the function of the vesicle coat protein clathrin. Clathrin-mediated endocytosis has recently been demonstrated also in plant cells, but its physiological and developmental roles remain unclear. Here, we assessed the roles of the clathrin-mediated mechanism of endocytosis in plants by genetic means. We interfered with clathrin heavy chain (CHC) function through mutants and dominant-negative approaches in Arabidopsis thaliana and established tools to manipulate clathrin function in a cell type-specific manner. The chc2 single mutants and dominant-negative CHC1 (HUB) transgenic lines were defective in bulk endocytosis as well as in internalization of prominent plasma membrane proteins. Interference with clathrin-mediated endocytosis led to defects in constitutive endocytic recycling of PIN auxin transporters and their polar distribution in embryos and roots. Consistent with this, these lines had altered auxin distribution patterns and associated auxin transport-related phenotypes, such as aberrant embryo patterning, imperfect cotyledon specification, agravitropic growth, and impaired lateral root organogenesis. Together, these data demonstrate a fundamental role for clathrin function in cell polarity, growth, patterning, and organogenesis in plants
Progress in Studies of Plant Homologs of Mitogen-Activated Protein (MAP) Kinase and Potential Upstream Components in Kinase Cascades
No full textProtein encoded by oncogene 6b from Agrobacterium tumefaciens has a reprogramming potential and histone chaperone-like activity
No full textCrown gall tumors are formed mainly by actions of a group of genes in the T-DNA that is transferred from Agrobacterium tumefaciens and integrated into the nuclear DNA of host plants. These genes encode enzymes for biosynthesis of auxin and cytokinin in plant cells. Gene 6b in the T-DNA affects tumor morphology and this gene alone is able to induce small tumors on certain plant species. In addition, unorganized calli are induced from leaf discs of tobacco that are incubated on phytohormone-free media; shooty teratomas and morphologically abnormal plants, which might be due to enhanced competence of cell division and meristematic states, are regenerated from the calli. Thus, the 6b gene appears to stimulate a reprogramming process in plants. To uncover mechanisms behind this process, various approaches including the yeast-two-hybrid system have been exploited and histone H3 was identified as one of the proteins that interact with 6b. It has been also demonstrated that 6b acts as a histone H3 chaperon in vitro and affects the expression of various genes related to cell division competence and the maintenance of meristematic states. We discuss current views on a role of 6b protein in tumorigenesis and reprogramming in plants
Fluorescence imaging-based screen identifies ARF GEF component of early endosomal trafficking
No full textEndocytic vesicle trafficking is crucial for regulating activity and localization of plasma membrane components, but the process Is still poorly genetically defined In plants. Membrane proteins of the PIN-FORMED (PIN) family exhibit polar localization In plant cells and facilitate cellular efflux of the plant hormone auxin, thereby regulating multiple developmental processes [1, 2]. PIN proteins undergo constitutive endocytosis and GNOM ARF GEF-dependent recycling [3-5], and their localization Is under extensive regulation by developmental and environmental cues [6-9]. We designed a fluorescence Imaging-based screen to Identify Arabidopsis thaliana mutants defective in internalization of proteins including PINs from the plasma membrane. We Identified three mutant loci, BFA-visualized endocytic trafficking defective1 (ben1) through ben3that do not efficiently accumulate PIN1-GFP In Intracellular compartments after Inhibition of recycling and secretion by fungal toxin brefeldin A (BFA). Fine mapping revealed that BEN1 encodes an ARF GEF vesicle trafficking regulator from the functionally uncharacterized BIG class. ben 1 mutant has been previously Implicated in pathogen response [10] and shows cell polarity, BFA sensitivity, and growth defects. BEN1 is Involved in endocytosis of plasma membrane proteins and localizes to early endocytic compartments distinct from GNOM-positive endosomes. Our results Identify BEN1 as the ARF GEF mediating early endosomal traffic
Fluorination of Ketones Using Iodotoluene Difluoride
No full textFluorination of ketones was achieved by the reaction of silyl enol ethers with iodotoluene difluoride in the presence of BF3·OEt2 and a Et3N·HF complex
α-Fluorination of β-dicarbonyl compounds using p-iodotoluene difluoride under neutral conditions
No full textA selective introduction of a fluorine atom into the α-position of β-dicarbonyl compounds was achieved using p-iodotoluene difluoride. The reaction proceeded under mild conditions and monofluorination of β-ketoesters, ketoamides, and diketones selectively took place
Oncogene 6b from Agrobacterium tumefaciens Induces Abaxial Cell Division at Late Stages of Leaf Development and Modifies Vascular Development in Petioles
No full textFluorescence Imaging-Based Screen Identifies ARF GEF Component of Early Endosomal Trafficking
No full textSemantic web link analysis to discover social relationship in academic communities
No full textTo discover how precisely links among researchers’ Web sites capture the ties of academic communities, this study conducts Web citation analysis. 3,878 Web sites of computer scientists and their 8,811 articles are assessed. 200 most frequently cited researchers from them are subjected to Web author cocitation analysis and compared to bibliographical data. As a result, a cluster of researchers on the Web becomes a superset of bibliographical one, that is, a community representing a larger research field. We then develop Web link ontology that defines various relationships among researchers to apply metadata annotation to the links among 200 sites. Findings: 1) since intellectual ties analysis separates off sociocognitive ties, it results into a better approximation of bibliographical author cocitation, 2) since sociocognitive ties analysis can utilize various links not only coauthor networks, diverse kinds of social connections can be found, 3) merging intellectual ties and sociocognitive ties analyses detect gatekeepers who bridges research fields on social networks. 1
Study of Abū Tālib al-Makkī
No full textThe aims of this thesis are to evaluate the present status of scholarship on Abū Tālib al-Makkī (d. 386/996) and to expand the basis of further research on him by
analysing him in a multi-dimensional way. This study challenges the conventional
view that al-Makkī’s Qūt al-qulūb (‘The Nourishment of Hearts’) is a Sufi work.
Part 1 introduces modern scholarship on al-Makkī. It also demonstrates
several issues which are tackled in this thesis. The present study focuses on a
metaphorical image of the heart, which is also shared in various cultures. By looking
at this common idea, Part 2 first attempts to explore the nature of the Qūt within the
context of Sufism and religion in general. This part provides a summarised
translation of part of the Qūt, where the author elucidates his view of the heart. The
intention of this annotated translation is to provide easy access to the key thought of
al-Makkī in the Qūt, for the first time in English, on the basis of a critical edition of
this book. Lastly Part 2 discusses the authenticity of al-Makkī’s alleged work, Ilm
al-qulūb (‘The Knowledge of Hearts’).
Part 3 analyses the influence of al-Makkī within and beyond Islam.
Considering the limited area of the study of al-Makkī , this part first examines
numerous works in various fields from his time until the twelfth/eighteenth century.
This is to evaluate how he was perceived in Muslim scholarship and to explore areas
which have not been discussed thoroughly before. Finally this thesis looks at the
Andalusian Jewish scholar, Ibn Bāqūdā(d. some time after 472/1080) and his book
al-Hidāya ilā farā'id al-qulūb (‘The Right Guidance to the Religious Duties of
Hearts’). A possible link between the two authors has been sometimes pointed out;
however, it has not been studied exhaustively.
Through exploring various aspects of al-Makkī and his writing, the present
thesis attempts to open up the study of the Qūt beyond Sufism and to offer an
opportunity to give further thought on the essential features of the mystical
dimensions of Islam
