Plant stem cells: The only constant thing is change

AbstractRecent studies in Arabidopsis have uncovered a negative feedback loop that couples the antagonistic functions of the WUSCHEL and CLAVATA loci to control stem cell fate in the shoot apical meristem. Abundance of the CLAVATA3 protein limits signaling through this pathway

Plant Meristems: The Fiendish SU DOKU of Stem-Cell Maintenance

Three recent studies have uncovered effector mechanisms and novel pathways in the regulation of the dynamic changes to cell behaviour that occur in plant meristems. The results show how exquisite regulation of cell-cycle mechanisms is central to root stem cell homeostasis

Romanticism and Ruralism: Changing 19th-Century American Perceptions of the Natural World

This is a digital public history research initiative that examines the correlation between European Romantic art and literature and 19th century American culture, particularly in regards to perspectives the natural world, landscape painting, landscape design and institutional reform. Romantic ideology was transplanted into American culture through the mediums of art and design. The creation of visual representations of the natural world through landscape art and architecture provided the American populace with a means of understanding and appreciating the natural world, and of seeing themselves as a viable part of it. Using an interdisciplinary approach, the presentation utilizes art history, cultural anthropology and material culture history as a means of understanding the growing sensitivity between the individual and the natural world in 19th century America

Allelic variation in HLA-B and HLA-C sequences and the evolution of the HLA-B alleles

Several new HLA-B (B8, B51, Bw62)- and HLA-C (Cw6, Cw7)-specific genes were isolated either as genomic cosmid or cDNA clones to study the diversity of HLA antigens. The allele specificities were identified by sequence analysis in comparison with published HLAB and -C sequences, by transfection experiments, and Southern and northern blot analysis using oligonucleotide probes. Comparison of the classical HLA-A, -B, and -C sequences reveals that allele-specific substitutions seem to be rare events. HLA-B51 codes only for one allelespecific residue: arginine at position 81 located on the cd helix, pointing toward the antigen binding site. HLA-B8 contains an acidic substitution in amino acid position 9 on the first central/3 sheet which might affect antigen binding capacity, perhaps in combination with the rare replacement at position 67 (F) on the Alpha-l helix. HLA-B8 shows greatest homology to HLA-Bw42, -Bw41, -B7, and -Bw60 antigens, all of which lack the conserved restriction sites Pst I at position 180 and Sac I at position 131. Both sites associated with amino acid replacements seem to be genetic markers of an evolutionary split of the HLA-B alleles, which is also observed in the leader sequences. HLA-Cw7 shows 98% sequence identity to the JY328 gene. In general, the HLA-C alleles display lower levels of variability in the highly polymorphic regions of the Alpha 1 and Alpha 2 domains, and have more distinct patterns of locusspecific residues in the transmembrane and cytoplasmic domains. Thus we propose a more recent origin for the HLA-C locus