Developmental biology of wood formation

The wood-forming vascular cambium is responsible for the production of a large part of the biomass on this planet. Yet, there is only limited knowledge on how cell proliferation and differentiation in the cambial meristem are regulated. In this thesis the wood-forming tissues of aspen were used as a model system to identify and characterize molecular factors related to cambial meristem activity. An important regulator of cambial meristem activity is the plant hormone auxin. As polar transport is crucial for the delivery of auxin to the cambial zone, we identified homologues of known regulators of polar auxin transport and described their regulation by environmental and developmental factors. Translating changes in auxin concentration into changes in gene expression involves members of the Aux/IAA gene family. Aspen homologues of Aux/IAA genes were cloned and found to be expressed in a highly tissue-specific fashion, which is further influenced by developmental events and changes in the environment. A major response of trees to environmental changes is the suspension of meristematic growth during winter dormancy. A comparison of gene expression in active and dormant cambia revealed dramatic changes in the transcriptome including the expression of many cold and stress related genes during winter. During the process of wood formation, cells originating in the vascular cambium go through an elaborate process of cell division, cell expansion, secondary wall formation and programmed cell death. Large-scale analysis of gene expression was used to create transcriptional maps of the differentiation process. This extensive dataset allowed us to confirm the proposed functions of various genes involved in wood formation, assign other known genes to specific stages along the developmental gradient and identify a large number of novel potential regulators of wood formation. The data further suggest that the cambial meristem shares regulatory mechanisms with other meristems in addition to its own, specific factors

Die Smart Library UB Hildesheim

Der Beitrag benennt die aufgrund überholter Gebäudetechnik erforderlichen Modernisierungsmaßnahmen auf der Grundlage netzbasierter Steuerungstechniken, umgesetzt im Rahmen eines Forschungsprojekts und in Zusammenarbeit mit Studierenden der Studiengänge "Umweltsicherung" und "Umweltwissenschaft und Naturschutz" der Universität Hildesheim und zwei mittelständischen Firmen. Ziel ist die Reduzierung des Energieverbrauchs und die Erhöhung der Lern- und Arbeitsqualität durch den Einsatz digital gesteuerter Heizungsventile sowie Jalousie- und Lüftermotoren, die über eine zentral funkgesteuerte Gebäudeleittechnik kontrolliert wird. Es handelt sich um ein Referenzobjekt, das auch über die eigene Nutzung hinaus anwendbar ist.This paper outlines the required modernisation measures due to out-ofdate building technology based on networked-based control technology, implemented in the context of a research project and in collaboration with students of "Environmental Protection" and "Environmental Science and Nature Protection" at Hildesheim University. Other partners were two middle-sized companies. The aim is to reduce power consumption and to improve the quality of learning and work by using digitally controlled heating valves as well as Venetian blinds and ventilator motors, which are controlled and monitored from a centrally radiocontrolled building services management system. This is a building which can be used as a reference point for other projects as the results are generally applicable

“Did you already post that in our library channel?” – instant messaging as a tool to improve staff engagement in discussing user-related issues

Effective communication is an essential part of good organisational culture. Tools like instant messaging offer new opportunities for improved communication – in our case, among library staff. The question we aim to answer is: Does instant messaging improve staff engagement concerning user-related issues

Do They Really Know What They Need? Prototypes and Different Research Methods as a Means of Testing Students‘Feedback – A Case-Study

Adopting a demand-oriented perspective helps librarians to understand their users better. Involving them in ongoing changes has the potential to have a lasting positive effect on the satisfaction of existing users and the recruitment of new ones. Three case-studies, which involved creating new learning spaces at the University Library of Hildesheim lead to the understanding that librarians need to employ attitudinal and behavioural research techniques to reach that goal because users – as it turns out – often do not really know what they need until they get a chance to try it

A High-Resolution Transcript Profile across the Wood-Forming Meristem of Poplar Identifies Potential Regulators of Cambial Stem Cell Identity

Plant growth is the result of cell proliferation in meristems, which requires a careful balance between the formation of new tissue and the maintenance of a set of undifferentiated stem cells. Recent studies have provided important information on several genetic networks responsible for stem cell maintenance and regulation of cell differentiation in the apical meristems of shoots and roots. Nothing, however, is known about the regulatory networks in secondary meristems like the vascular cambium of trees. We have made use of the large size and highly regular layered organization of the cambial meristem to create a high-resolution transcriptional map covering 220 μm of the cambial region of aspen (Populus tremula). Clusters of differentially expressed genes revealed substantial differences in the transcriptomes of the six anatomically homogenous cell layers in the meristem zone. Based on transcriptional and anatomical data, we present a model for the position of the stem cells and the proliferating mother cells in the cambial zone. We also provide sets of marker genes for different stages of xylem and phloem differentiation and identify potential regulators of cambial meristem activity. Interestingly, analysis of known regulators of apical meristem development indicates substantial similarity in regulatory networks between primary and secondary meristems

Activity–dormancy transition in the cambial meristem involves stage-specific modulation of auxin response in hybrid aspen

The molecular basis of short-day–induced growth cessation and dormancy in the meristems of perennial plants (e.g., forest trees growing in temperate and high-latitude regions) is poorly understood. Using global transcript profiling, we show distinct stage-specific alterations in auxin responsiveness of the transcriptome in the stem tissues during short-day–induced growth cessation and both the transition to and establishment of dormancy in the cambial meristem of hybrid aspen trees. This stage-specific modulation of auxin signaling appears to be controlled via distinct mechanisms. Whereas the induction of growth cessation in the cambium could involve induction of repressor auxin response factors (ARFs) and down-regulation of activator ARFs, dormancy is associated with perturbation of the activity of the SKP-Cullin-F-boxTIR (SCFTIR) complex, leading to potential stabilization of repressor auxin (AUX)/indole-3-acetic acid (IAA) proteins. Although the role of hormones, such as abscisic acid (ABA) and gibberellic acid (GA), in growth cessation and dormancy is well established, our data now implicate auxin in this process. Importantly, in contrast to most developmental processes in which regulation by auxin involves changes in cellular auxin contents, day-length–regulated induction of cambial growth cessation and dormancy involves changes in auxin responses rather than auxin content

Expansins Abundant in Secondary Xylem Belong to Subgroup A of the α-Expansin Gene Family

Differentiation of xylem cells in dicotyledonous plants involves expansion of the radial primary cell walls and intrusive tip growth of cambial derivative cells prior to the deposition of a thick secondary wall essential for xylem function. Expansins are cell wall-residing proteins that have an ability to plasticize the cellulose-hemicellulose network of primary walls. We found expansin activity in proteins extracted from the cambial region of mature stems in a model tree species hybrid aspen (Populus tremula × Populus tremuloides Michx). We identified three α-expansin genes (PttEXP1, PttEXP2, and PttEXP8) and one β-expansin gene (PttEXPB1) in a cambial region expressed sequence tag library, among which PttEXP1 was most abundantly represented. Northern-blot analyses in aspen vegetative organs and tissues showed that PttEXP1 was specifically expressed in mature stems exhibiting secondary growth, where it was present in the cambium and in the radial expansion zone. By contrast, PttEXP2 was mostly expressed in developing leaves. In situ reverse transcription-PCR provided evidence for accumulation of mRNA of PttEXP1 along with ribosomal rRNA at the tips of intrusively growing xylem fibers, suggesting that PttEXP1 protein has a role in intrusive tip growth. An examination of tension wood and leaf cDNA libraries identified another expansin, PttEXP5, very similar to PttEXP1, as the major expansin in developing tension wood, while PttEXP3 was the major expansin expressed in developing leaves. Comparative analysis of expansins expressed in woody stems in aspen, Arabidopsis, and pine showed that the most abundantly expressed expansins share sequence similarities, belonging to the subfamily A of α-expansins and having two conserved motifs at the beginning and end of the mature protein, RIPVG and KNFRV, respectively. This conservation suggests that these genes may share a specialized, not yet identified function