No description available.

Thesis (Ph. D.)--University of Chicago. / Reprinted from the Botanical gazette, v. 40, p. 12-48, July, 1905. Also issued as Contributions from the Hull botanical laboratory. LXXIV. Bibliography: p. 43-47.

Thesis (Ph. D.)--University of Chicago. / Reprinted from the Botanical gazette, v. 40, p. 12-48, July, 1905. Also issued as Contributions from the Hull botanical laboratory. LXXIV. Bibliography: p. 43-47.

Thesis (doctoral)--Helsinki University of Technology, 2007. / Includes bibliographical references. Also available on the World Wide Web.

The distribution of epidermal hairs (trichomes) is an important taxonomic character in the genus Antirrhinum. Most species in subsection Antirrhinum produce trichomes from lower internodes and leaves, then have bald stems and leaf blades after the third node and resume trichomes production again in the inflorescence (the "bald" phenotype). All species in subsection Kickxiella produce trichomes throughout development (the "hairy" phenotype). Populations of some species are polymorphic for trichome distribution-both bald and hairy individuals were observed in A. australe, A. graniticum, A. latifolium and A. meonanthum. Antirrhinum species also varied in trichome morphology. Five types were recognized according to length and the presence or absence of a secretory gland. Some types were present in all species and had similar distributions-for example short glandular trichomes were found on the adaxial midribs of all leaves in all species, and the lower leaves and internodes of all species shared longer glandular and long eglandular trichomes. However, the trichomes on leaf blades and stems at higher vegetative nodes of hairy species and in the inflorescences differed in morphology between species, suggesting that they are regulated differently from trichomes at more basal positions. Other species in the tribe Antirrhineae showed similar variation in trichome morphology and distribution to Antirrhinum, suggesting that the control of trichome development might be conserved within the tribe. To understand the genetic basis for variation in trichome distribution, a near-isogenic line (NIL) was generated by introducing regions of the genome of A. charidemi (hairy, subsection Kickxiella) into the genetic background of A. majus subsp. majus (bald, subsection Antirrhinum). One NIL segregated bald and hairy progeny, with the same trichome distributions as the parent species, in a ratio that suggested a single locus is responsible for the differences and baldness is dominant. The locus was named as Hairy and assumed to act as a suppressor of trichome formation. Progeny of the NIL were used in genome resequencing of bulked phenotype pools (Pool-seq) to map Hairy. No recombination between Hairy and a candidate gene (GRX1) from the Glutaredoxin gene family, was detected in the mapping population. In addition, RNA-seq revealed that GRX1 was expressed in bald parts of bald progeny, but not in the same parts of hairy progeny, and in situ hybridisation showed GRX1 RNA was restricted to epidermal cells, which form trichomes in the absence of Hairy activity. A virus-induced gene silencing (VIGS) method was also developed to test GRX1 function further. Reducing GRX1 activity allowed ectopic trichome formation in the bald NIL. Together, this evidence strongly supported Hairy being GRX1. To investigate evolution of Hairy and its relationship to variation in trichome distribution, the NIL was crossed to other Antirrhinum species. These allelism tests suggested that Hairy underlies variation in trichome distribution throughout the genus, with the exception of A. siculum, which has a bald phenotype but might lack activity of hairy and a gene needed for trichome formation. Hairy sequences were obtained from representative of 24 Antirrhinum species and two related species in the tribe Antirrhineae. The conserved trichome-suppressing function of the sequence from one of these species (Misopates orontium, bald phenotype) was confirmed by VIGS. Gene phylogenies combined with RNA expression analysis suggested that the ancestral Antirrhinum had a bald phenotype, that a single mutation could have given rise to the hairy alleles in the majority of Kickxiella species, that these alleles were also present in polymorphic populations in the other subsections, consistent with transfer from Kickxiella by hybridisation, and that multiple, independent mutations had been involved in parallel evolution of the hairy phenotype in a minority of Kickxiella species. Phylogenetic analysis of GRX proteins suggested that Hairy gained its trichome-repressing function relatively late in the evolutionary history of eudicots, after the Antirrhineae-Phrymoideae split, but before divergence of the lineages leading to Antirrhinum and Misopates. A yeast two-hybrid screen identified members of the TGA and HD-Zip IV transcription factors as potential substrates of the Hairy GRX.

The endosomal trafficking system is a network of highly coordinated cellular pathways that control the growth and function of cells. The coordination of secretion and endocytosis in cells is one of the primary drivers of polarized growth, where new plasma membrane and cell wall components are deposited at the growing apex. In plants, one of the cell types exhibiting polarized growth are the root hairs. Root hairs are regulated extensions of epidermal cells called trichoblasts and are essential for anchorage, absorption of water and nutrients, and plant-microbe interactions. In this thesis, I characterize a previously undescribed protein involved in retromer function and endosomal trafficking pathways that regulate tip growth in root hairs of Arabidopsis thaliana. The large retromer complex functions in recycling receptors in endosomal trafficking pathways essential for diverse developmental programs including cell polarity, programmed cell death, and shoot gravitropism in the model plant, Arabidopsis thaliana. I have characterized VPS26C, a novel member of the large retromer complex, that is essential in maintaining root hair growth in Arabidopsis. We used Bimolecular Fluorescence Complementation (BiFC) analysis to demonstrate thatVPS26C interacts with previously characterized core retromer subunits VPS35A and VPS29. Genetic analysis also indicates that vps26c suppresses the root hair growth and cell wall organization phenotypes of a null mutant of the SNARE VTI13 that localizes to early endosomes and the vacuole membrane, indicating a crosstalk between the VPS26C-retromer and VTI13-dependent vesicular trafficking pathways. Phylogenetic analysis was used to show that VPS26C genes are present in most angiosperms but appear to be absent in monocot genomes. Moreover, using a genetic complementation assay, we have demonstrated that VPS26C shares deep conservation of biochemical function with its human ortholog (DSCR3/VPS26C). We also used an affinity purification-based proteomic analysis to identify proteins associated with VTI13 in young seedlings. Preliminary results suggest that a number of proteins linked to cell plate organization in plants are associated with the VTI13 proteome, emphasizing the potential role of this pathway in new cell wall biosynthesis/organization. Additionally, we have identified endoplasmic reticulum (ER)-body proteins, involved in plant defense response pathways, suggesting that either the VTI13 endosomal trafficking pathway is functioning in plant defense responses, or the ER-body proteins have additional independent function(s) in Arabidopsis roots that depend on VTI13. In summary, I have described a novel retromer complex essential for polarized growth in Arabidopsis. VPS26C is an ancient gene and shares sequence and functional homology between human and Arabidopsis. vps26c is a genetic suppressor of the vti13- dependent root hair growth and cell wall organization pathways. Proteomic analysis of VTI13 endosomes in young seedlings suggests that a number of proteins associated with cell plate formation are associated with VTI13 compartments, supporting the genetic analysis described here and serves as a starting point to further describe the role of this pathway in controlling polarized growth in plants.

Myosin proteins function as molecular motors that drive the ATP-dependent movement of cellular components along actin filaments. Vascular plants encode two different types of myosin, referred to as class VIII and class XI. Although class XI myosins have been suggested to function in organelle movement and cytoplasmic streaming, little is known about their cellular function in detail. The Arabidopsis genome encodes 13 class XI myosin genes. The reasons for the relatively large number of myosin XI isoforms present within a single plant species are unknown. To investigate the function of these gene products in the cell, we determined the spatial and temporal gene expression patterns by constructing promoter-reporter plants. Myosin genes are expressed in a variety of tissues with substantial overlap between family members. To study the biological function more intensively, homozygous T-DNA insertion lines were isolated for all 13 genes. Interestingly, five mutants showed phenotypes related to root hairs. mya2, xi-b, and xi-k showed shorter root hairs than in wild type while xi-h and mya1 produced a higher density of root hairs on the epidermis. MYA1 and XI-K are the most similar isoforms among the 13 myosins and their double mutant showed an additive phenotype with extremely short root hairs suggesting that these two myosins have partially redundant functions. Interestingly organelle movements, especially those of peroxisomes, were reduced in mya1 xi-k. Tip growth is the key growth mechanism in root hairs and pollen tubes. Many kinds of vesicles are trafficking toward (or backward from) the apical dome of root hairs to supply membrane and cell wall material as well as energy for growing tips. These movements along the shank of the hair occurred with velocities around 2 to 3 μm/s for Arabidopsis thaliana. In xi-k mutants, root hairs grew more slowly and terminated sooner than in wild type. Interestingly, this reduction of growth rate was correlated with a fluctuation of YFP-RAbA4b accumulation at the tip of growing root hairs. Other markers, including PI4P lipid and ER, as well as calcium and actin dynamics did not show significant differences. A YFP-XI-K construct driven by its native promoter could rescue the mutant phenotype and revealed accumulation of this myosin in the tip of growing root hairs. The distribution of YFP-XI-K in the root hair tip partially overlapped with CFP-RHD4-labeled vesicles at the subapex and YFP-RabA4b vesicles at the apex of root hairs, suggesting that myosin XI-K might be involved in the accumulation of unidentified vesicles in the tip of growing root hairs. Characterization of two mutants that showed ectopic root hair growth in the epidermis, resulting in a higher density of root hairs than wild type, mya1 and xi-h, were initiated with two analyses. At first, staining pattern of promoter-reporter constructs of three key transcription factors, WER, EGL3, and GL2 were observed in mya1. Although variation in individual samples was too large to conclude, GL2 staining patterns in mya1 occasionally were unorganized. Increasing sample population and detail study is necessary. Secondly, effects of phosphate deficiency were observed with the mya1 and the xi-h in series of phosphate concentrations ranging from 1μM to 300μM. The xi-h mutant showed insensitivity on root hair production upon phosphate deficiency, suggesting a potential function of XI-H in the response to phosphate deficiency. Confirmation of these results and further study of the MYA1 and the XI-H is essential. In summary, this study established a systematic approach to investigate the biological function of class XI myosins in plant development and significantly increases our understanding of the function of XI-K myosin in root hair tip growth.

Thèse réalisée en cotutelle avec la direction de Jean-Jacques Courtine à l'Université de Paris III Sorbonne Nouvelle sous la discipline anthropologie et avec la direction de Dominique Deslandres à l'Université de Montréal sous la discipline histoire / À cheval entre nature et culture, le poil et la chevelure humaine condensent un grand ensemble d’enjeux symboliques relevant de questions identitaires, religieuses, scientifiques, et autres. L’étude des discours et des pratiques concernant le poil représente, pour l’historien, une fenêtre sur l’évolution des mentalités d’une société donnée en ce qui concerne les perceptions de soi et de l’autre. S’inscrivant dans le courant intellectuel de l’histoire du corps, cette thèse s’intéresse plus précisément aux « systèmes trichologiques » dans la France de l’époque moderne (soit du XVIe au XVIIIe siècle). Elle se fonde sur l’analyse d’une grande variété de sources permettant de recouper différents types de discours touchant au poil : point de vue scientifique des médecins, physiognomonistes et historiens, point de vue prescriptif des traités d’éducation et de civilité, contrepoint exotique des récits de voyage et autres témoignages de « curiosités » ainsi qu’un suivi de l’évolution étymologique des mots pertinents au sein de dictionnaires et encyclopédies. La question centrale de cette thèse est celle du rôle du poil dans le façonnement de représentations servant à identifier, démarquer et hiérarchiser les groupes sociaux; et comment celles-ci évoluent de concert avec d’autres transformations historiques. Le premier chapitre s’intéresse au poil comme marqueur de différences individuelles. On y retrace une sorte de « langage » du poil, recensant les significations et connotations rattachées aux diverses manifestations pileuses : couleur, longueur, abondance, forme. Il y apparaît clairement que le poil joue un rôle important tant dans la mise en scène de soi que dans la lecture de l’apparence physique de l’autre. Le deuxième chapitre s’intéresse au poil en tant que marqueur de « genre ». On y examine la contribution des représentations de la pilosité dans la construction des identités masculines et féminines. Le poil s’interprète comme une manifestation extérieure de la nature des différents sexes et de leurs rôles dans la société, ce qui en fait un enjeu dans les relations de pouvoir entre les sexes et entre les gens du même sexe. Le troisième chapitre aborde le poil en ce qu’il permet de délimiter et hiérarchiser les classes sociales. On le voit participer aux modes et au processus de discipline des corps qui permettent aux élites, avec les perruques et le raffinement des conduites et des pratiques d’embellissement, de se distinguer autrement que par les vêtements. On retrace également une politique du poil qui s’étend au-delà du regard, l’état s’accordant le droit d’agir directement sur les corps – les chevelures, les poils – de ses sujets. Le dernier chapitre explore l’instrumentalisation du poil dans la construction d’un « autre » lointain et anormal : le sauvage d’outre-mer, l’enfant-loup, l’aberration de la nature. En caractérisant les poils de cas qu’ils situent aux frontières de l’humanité, les Français de l’Ancien régime exposent leurs propres présupposés sur la normalité et la civilisation. Cette thèse aboutit à un principe qui réunit et organise les signes de reconnaissance du poil à partir du regard construit et normé de ses propres poils que j’ai nommé « pilocentrisme ». Permettant de mettre en lumière le rôle du système pileux dans les modèles d’identification et de hiérarchisation, le concept de pilocentrisme peut ainsi servir de nouvelle catégorie d’analyse pour étudier les rapports de pouvoir dans l’histoire. / Both a natural and cultural phenomenon, human hair condenses a wide array of symbolic issues relating to notions of identity, religion, science, etc. The analysis of discourses and practices concerning hair affords the historian a window on the evolution of a given society’s attitudes towards the self and others. Following the historiographical current of the history of the body, this thesis examines the “trichological systems” of modern France (16th to 18th centuries). It is based on a wide variety of sources, allowing the comparison of different types of hair-related discourses: the scientific point of view of physicians, physiognomonists and historians; the prescriptive point of view of education and civility treatises; the exotic counterpoint of travel narratives and other writings on “curiosities”, as well as a review of the etymological evolution of relevant words in dictionaries and encyclopedias. The central question in this dissertation concerns the role of hair in the construction of representations used in identifying, distinguishing and ranking social groups; and how these representations evolve along with other historical transformations. The first chapter highlights hair’s role as marker of individual differences. A “language of hair” is exposed, inventorying meanings and connotations attached to the various factors of hairy manifestations: color, length, affluence, shape. The importance of hair in the staging of the self and the reading of others is highlighted. The second chapter explores the contribution of hair to the construction of gendered identities. Hair is interpreted as an outward sign of the sexes’ different natures and the confirmation of their respective social roles. As such, it is a tool in the negotiation of power between and within genders. The third chapter examines hair as it is used in the demarcation of social classes. It is seen as participating in the process of body discipline of the French elite. The use of wigs alongside refined hair care emphasized their distinction from lower classes beyond the traditional means of clothing. Direct state regulations on the hair of its subjects also show that trichological politics did not limit themselves to the gaze. The finale chapter highlights the instrumentalization of hair in the construction of faraway and abnormal “others”: the overseas savage, the wolf child, the natural aberration. By characterizing the hair of beings at the frontier of humanity, Ancien Régime French exposed their own presuppositions on normality and civilization. This dissertation develops the notion of “pilocentrism”, uniting and organizing the various modes of interpretation of hairs on the basis of the constructed and normed perception of one’s own. Shedding a new light on the role of hair representation systems on models of identification and hierarchisation, the notion of pilocentrism can serve as a new analytical category to study historical power dynamics.

Yes / BACKGROUND: Diffuse alopecia areata (DAA) often leads to a complete hair shedding within a few months. OBJECTIVE: To explore features and mechanisms underlying DAA. MATERIALS AND METHODS: Scalp and hair root dermoscopy were conducted on 23 DAA patients throughout the disease process, 20 patchy Alopecia areata patients, 23 acute telogen effluvium (ATE) patients and 10 normal controls. Histopathology was also evaluated. RESULTS: We found almost all hair roots were anagen in early stage DAA in 18 patients (18/23, 78.3%) within the first 4-8 weeks after hair loss onset. Anagen effluvium (~4 weeks) was followed by catagen (~4 weeks) and then telogen/exogen (~8 weeks) effluvium with overlap. Hair root and proximal hair shaft depigmentation was more prominent in later DAA disease stages. Black dots, exclamation mark hairs and inconsistent thickness of hair shafts were found more often in early than later DAA (Ps < 0.01). Early DAA histopathology revealed more prominent inflammation and hair follicle regression than that observed in the later stages. Patchy alopecia areata patients showed mixed anagen, catagen and telogen hair roots while ATE patients showed increased exogen and mildly decreased hair root pigmentation. CONCLUSION: Sequential cyclic staging of shed hairs in DAA indicates the insult may be hair-cycle specific. We suggest that DAA is initially an anagen effluvium disease involving an intense inflammatory insult, later progressing to a brief catagen effluvium, and then to telogen effluvium with premature exogen, in later stages of DAA. / This study was supported by the following grants to Xingqi Zhang: National Natural Science Foundation of China (81573066); Natural Science Foundation of Guangdong Province (2014A030313098).

Pflanzenwurzeln reagieren auf Phosphat- oder Eisenmangel mit einer vermehrten Wurzelhaarbildung, was eine Vergrößerung der absorptiven Oberfläche bewirkt. Die erhöhte Anzahl an Wurzelhaaren wird dabei auf verschiedene Weise gebildet. Phosphat-defiziente Arabidopsis-Pflanzen erhöhen die Anzahl an Wurzelhaarzellen, während sich unter Eisenmangel verzweigte Wurzelhaare entwickeln. Die Fe- und P-Homöostase wird durch systemische und lokale Signalwege reguliert. Der Einfluss dieser Signale auf die Fe- bzw. Psensitive Wurzelhaarentwicklung wurde mithilfe von split-root-Experimenten untersucht, die mit einem systemischen Mangel- oder Suffizienzsignal kombiniert wurden. Die Verzweigung der Wurzelhaare Fe-defizienter Pflanzen wurde durch ein dominantes Suffizienzsignal reprimiert, unabhängig von seiner lokalen oder systemischen Herkunft. Die Erhöhung der Wurzelhaarzahl bei P-Mangelpflanzen wurde durch ein dominantes Defizienzsignal induziert. Um herauszufinden, welches Entwicklungsstadium von dem jeweiligen Nährstoff beeinflusst wird, wurden Mutanten mit Defekten in frühen und späten Wurzelhaarentwicklungsstadien untersucht. Mutanten mit beeiträchtigter Wurzelhaar-Spezifikation wichen in ihrer Wurzelhaarzahl und –lokalisation vom Wildtyp ab, zeigten aber eine Fe- oder P-sensitive Veränderung. Die Gene aus frühen Entwicklungsstadien sind demnach essentiell für die Reaktion, sind aber nicht das direkte Ziel der Mangelsignale. Frühe Zelleigenschaften in der meristematischen Region waren durch die Eisen- oder Phosphatverfügbarkeit nicht verändert, was darauf hindeutet, dass die Wurzelhaarbildung erst in einem späteren Entwicklungsstadium durch die Nährstoffe beeinflusst wird. Mutanten mit Defekten in späteren Entwicklungsstadien zeigten kurze oder verformte Wurzelhaare unabhängig von der Nährstoffversorgung. Das Fe- oder P-Signal mündet also vor der Wirkung dieser Komponenten in die Wurzelhaarbildung ein. Das heisst, nachdem die korrekte Wurzelhaar-Position und -Anzahl in Anpassung an das Fe- oder P-Angebot festgelegt wurde, werden die Wurzelhaare unter allen Wachstumsbedingungen von einer gemeinsamen Maschinerie elongiert. Zur Identifikation potentiell neuer Gene, die die Wurzelhaarbildung in Anpassung an P-Mangel regulieren, wurden sechs Mutanten isoliert, die keine Wurzelhaare bei P-Mangel bilden, aber nach dem Transfer auf P-suffizientes Medium nicht beeinträchtigt waren. Eine dieser Mutanten, per2, wurde phänotypisch und genetisch charakterisiert. Neben der veränderten Wurzelhaarbildung zeigte per2 auch eine konstitutiv erhöhte Lateralwurzelbildung und eine erhöhte Anthozyan-Akkumulation bei P-Mangel. Laut epistatischen Analysen gehört die per2 Mutante zu einem Signalweg, der unabhängig von frühen Zellspezifikationsgenen wirkt. Der per2-Locus wurde innerhalb eines 87,5 kpb großen Abschnittes auf dem oberen Arm von Chromosom 3 kartiert. Mutanten die einen per2-ähnlichen Phänotyp zeigen, wurden bisher nicht beschrieben. Daher handelt es sich bei PER2 möglicherweise um ein neues Gen, das die Wurzelhaarbildung bei Phosphatmangel reguliert und weitere P-Mangelreaktionen beeinflusst. / Limitation of immobile nutrients, such as iron (Fe) and phosphate (P), induces the development of additional root hairs that lead to an increase of the absorptive surface of the root. The increased root hair frequency of Fe- and P-deficient Arabidopsis was realized by different strategies. Phosphate-deficient plants increased the number of root hairs while in Festarved plants root hairs were branched. The Fe and P starvation responses in plants are thought to be regulated by a systemic signaling mechanism that communicates the nutrient status of the shoot to the root and by a local signaling mechanism that perceives the Fe or P availability in the soil. The influence of local and systemic signals on the respective root hair phenotype was investigated in split-root experiments. This treatment was combined with either a nutrient-sufficient or -deficient shoot. The root hair branching typical of Fe-deficient plants only occured in the presence of both a local and a systemic Fe-deficiency signal. As a consequence, an Fe sufficiency signal acted dominantly to any deficiency signal, independent of its origin. The increased number of root hairs in P-deficient plants, conversely, was activated through either a local or a systemic P deficiency signal. Thus, the P deficiency signal acted dominantly to any sufficiency signal. To determine, which stage of root hair development was influenced by iron and phosphate, mutants with defects in different stages of root hair development were investigated for their root hair phenotype. Mutants affected in the early stages of root hair development, such as specification, displayed marked changes in the number and localization of root hairs. However, the nutritional signal was perceived and translated in this group of mutants. This indicates that the specification genes are involved in the nutrient-sensitive root hair formation, but may not be the direct targets. Early cell characteristics of root hairs in the late meristematic region of the root, like the expression of marker genes, were unaltered in plants adapted to Fe or P deficiency. This suggested the nutritional signal modulates root hair development after these characteristics have been established. Mutants with defects in the later stages of root hair development, such as root hair elongation, showed short or deformed root hairs in the proper position and frequency and were, thus, impaired independent of the Fe or P supply. Thus, the nutritional signal may enter the root hair developmental pathway around the stage of root hair initiation and bulge formation. Finally, six mutants were screened that did not form root hairs under P deficiency but developed normal, when the plants were transferred to P-sufficient medium. One of these mutants, per2 (phosphate deficiency root hair defective2), was characterized phenotypically and genetically. In addition to the impaired root hair growth, the per2 mutant displayed a constitutively high lateral root number and accumulated an increased amount of anthocyanins under P starvation. Epistatic analysis revealed that per2 action is independent of early cell specification genes. The per2 mutation was mapped to a 87.6 kbp region on the upper arm of chromosome 3 containing 19 genes. The per2 phenotype has not been described before. Thus, PER2 is a potential new gene involved in root hair development under phosphate deficiency.