Department of Developmental Genetics

Lehrstuhl für Entwicklungsgenetik

Prof. Dr. G. Jürgens

Veranstaltungen:
Wintersemester 1997/98

Arbeitsgruppen:
AG Prof. Dr. Jürgens und Dr. Mayer
AG Dr. Hülskamp
AG Dr. Laux

Overview


The fertilised egg cell gives rise to a multicellular organism with a distinct spatial arrangement of cell types, tissues and organs. Plant embryogenesis makes a seedling with a basic body plan to which groups of stem cells, the meristems, add new structures, such as leaves and flowers, to give the adult plant form.
Developmental processes involve specific cell activities. Cells adopt fates in response to information about their relative positions (pattern formation). Cells can divide differentially in time and space or expand along an axis, thus contributing to body or organ shape (morphogenesis). Differentiating cells can undergo distinct shape changes (cell morphogenesis). Plant cells are encased in an extracellular matrix, the cell wall, and neighboring cells are connected by plasmodesmata, cytoplasmic channels which can be regulated to faciliate the passage of large molecules. These conditions affect the ways plant cells divide, exchange developmental information and acquire distinct shapes.
Our research focuses on plant developmental mechanisms. Since the genetic approach is a very powerful strategy we use the model system Arabidopsis thaliana which offers a number of experimental advantages. Mutants with specific developmental defects can be isolated with limited labour, and genes identified by mutant phenotype can be cloned on the basis of their position within the genome (map-based cloning). Arabidopsis is easily transformed for functional studies in transgenic plants, and large populations of plants with T-DNA or transposon insertions can be screened for mutations in cloned genes ("reverse genetics").
We analyse how cell fate choices are made in several developmental contexts, such as embryogenesis, leaf epidermis and shoot meristem. Relevant genes are identified in large-scale mutagenesis screens, isolated by map-based cloning, and their expression is studied by in situ hybridisation and immuno-localisation. Molecular markers for different regions and tissues are generated by transposon mutagenesis to monitor the effects of mutations. Interactors of cloned developmental genes are identified by screening Arabidopsis cDNA libraries in the yeast two-hybrid system. We use these and other methods to analyse developmental problems in our projects.
Embryogenesis generates distinct regions along the apical-basal axis and different tissue layers across the axis. We are studying molecular and cellular mechanisms that establish this overall body organisation. The shoot meristem produces new organs during postembryonic development without being used up. We are analysing how cells, depending on their position within the meristem, either act as stem cells or give rise to new organs. Many differentiating cells attain characteristic shapes. Mechanisms underlying cell morphogenesis are addressed in two cell types, the trichome (leaf hair) and the pollen tube. Cytokinesis (cell division) is a basic biological process that is utilised in various ways during development. This research aims to elucidate mechanisms of cytokinesis, such as regulated vesicle trafficking and fusion to produce the cell plate. The following project descriptions give more detailed information about problems addressed, current research activities and future directions.