References: Hair growth and hair loss
Plant Physiol. 2002 Jun;129(2):638-49.
Regulation of the cell expansion gene RHD3 during Arabidopsis development.
Wang H, Lee MM, Schiefelbein JW.
Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, MI 48109-1048, USA.
The RHD3 (ROOT HAIR DEFECTIVE3) gene encodes a putative GTP-binding protein required for appropriate cell enlargement in Arabidopsis. To obtain insight into the mechanisms of RHD3 regulation, we conducted a molecular genetic dissection of RHD3 gene expression and function. Gene fusion and complementation studies show that the RHD3 gene is highly expressed throughout Arabidopsis development and is controlled by two major regulatory regions. One regulatory region is located between -1,500 and -600 bp upstream of the RHD3 gene and is required for vascular tissue expression. The other region is intragenically located and includes the 558-bp first intron, which is responsible for high-level expression of RHD3 throughout the plant. The presence and location of this intron is essential for gene function because constructs lacking this intron or constructs with the intron in an abnormal position are unable to functionally complement the rhd3 mutations. We also analyzed the role of other RHD genes and the plant hormones auxin and ethylene in RHD3 regulation, and we determined that these act downstream or independently from the RHD3 pathway. This study shows that multiple levels of regulation are employed to ensure the appropriate expression of RHD3 throughout Arabidopsis development.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12068108&dopt=Abstract
Plant Physiol. 2002 Jun;129(2):678-90.
Cytokinesis-defective mutants of Arabidopsis.
Sollner R, Glasser G, Wanner G, Somerville CR, Jurgens G, Assaad FF.
Genetics and Microbiology Institute, Ludwig Maximillian University, Maria Ward Strasse 1a, 80638 Munich, Germany.
We have identified mutations in six previously uncharacterized genes of Arabidopsis, named club, bublina, massue, rod, bloated, and bims, that are required for cytokinesis. The mutants are seedling lethal, have morphological abnormalities, and are characterized by cell wall stubs, gapped walls, and multinucleate cells. In these and other respects, the new mutants are phenotypically similar to knolle, keule, hinkel, and pleiade mutants. The mutants display a gradient of stomatal phenotypes, correlating roughly with the severity of their cytokinesis defect. Similarly, the extent to which the different mutant lines were capable of growing in tissue culture correlated well with the severity of the cytokinesis defect. Phenotypic analysis of the novel and previously characterized loci indicated that the secondary consequences of a primary defect in cytokinesis include anomalies in body organization, organ number, and cellular differentiation, as well as organ fusions and perturbations of the nuclear cycle. Two of the 10 loci are required for both cytokinesis and root hair morphogenesis. The results have implications for the identification of novel cytokinesis genes and highlight the mechanistic similarity between cytokinesis and root hair morphogenesis, two processes that result in a rapid deposition of new cell walls via polarized secretion.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12068111&dopt=Abstract
Dev Genes Evol. 2002 Jun;212(5):218-29. Epub 2002 Apr 12.
The genetic control of arista lateral morphogenesis in Drosophila.
He B, Adler PN.
Biology Department and Cancer Center, University of Virginia, Charlottesville, VA 22903, USA.
The sensory bristles and epidermal hairs of Drosophila have proven to be valuable model cell types for studying the role of the cytoskeleton in cellular morphogenesis. We have recently begun to use the arista laterals as a third model cell type. The laterals display a combination of bristle and hair characteristics and provide a system where we can compare the relative importance of specific genes and subcellular structures for the morphogenesis of different polarized cellular extensions. We have characterized the lateral phenotype of a collection of mutations selected because of their phenotypes in hairs and bristles. In many but not all ways the lateral phenotypes are similar to the hair and bristle phenotypes. We provide compelling genetic evidence for the importance of the actin cytoskeleton in lateral elongation, shaping and integrity. Our observations provide evidence that defects in actin bundling can destabilize laterals so that they split during growth. Temperature shift experiments suggest that a defect in lateral initiation can lead to subsequent splitting. These observations provide a link between multiple hair and lateral cells forming by both multiple initiation events and by the splitting of individual cellular extensions. We also found that mutations that lead to lateral splitting typically alter the stereotypic arrangement of actin filament bundles and microtubules in laterals.
online pharmacy ref. source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12070612&dopt=Abstract
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