Developmental regulation of pectic polysaccharides in the root meristem of Arabidopsis

JIM 5, an antibody that recognizes a relatively unesterifiedpectic epitope, distinguishes between dividing (meristematic)and non-dividing (central cells of the quiescent centre) cellsin the Arabidopsis root tip, indicating that non-dividing cellwalls contain higher levels of relatively unesterified pectinthan dividing cells. JIM 7, an antibody that recognizes a relativelymethyl esterified epitope, labels all cell walls uniformly throughoutthe root, suggesting that there is little variation in the relativelymethyl esterified pectic component in the two cell types. Theseobservations suggest that the characteristics of cell wallsin the root tip result in part from modulations in the amountof unesterified and non-methyl esterified pectin. Key words: Pectin, quiescent centre, roots, Arabidopsis     

Plasmodium falciparum protein associated with the invasion junction contains a conserved oxidoreductase domain

The merozoite cap protein-1 (MCP-1) of Plasmodium falciparum follows the distribution of the moving Junction during invasion of erythrocytes. We have cloned the gene encoding this protein from a cDNA library using a monoclonal antibody. The protein lacks a signal sequence and has no predicted trans-membrane domains; none of the antisera reacts with the surfaces of intact merozoites, indicating that the cap distribution is submembranous. MCP-1 is divided into three domains. The N-terminal domain includes a 52-amino-acid region that is highly conserved in a large family of bacterial and eukaryotic proteins. Based on the known functions of two proteins of this family and the pattern of amino acid conservation, it is predicted that this domain may possess oxido-reductase activity, since the active cysteine residue of this domain is invariant in all proteins of the family. The other two domains of MCP-1 are not found in any other members of this protein family and may reflect the specific function of MCP-1 in invasion. The middle domain is negatively charged and enriched in glutamate; the C-terminal domain is positively charged and enriched in lysine. By virtue of its positive charge, the C-terminal domain resembles domains in some cytoskeleton-associated proteins and may mediate the interaction of MCP-1 with cytoskeleton in Plasmodium.     

Ethylene is a positive regulator of root hair development in Arabidopsis thaliana

Evidence is provided that ethylene is a positive regulator of hair cell development in the root epidermis of Arabidopsis thaliana. Treatment of seedlings with increasing concentrations of the ethylene precursor, 1-aminocyclopropane-1-carboxylic acid (ACC) results in progressively more root hair cells developing in positions normally occupied by non-hair cells. Consistent with these findings are observations that treatments that block either ethylene synthesis or its perception reduce the number of root hairs. A model is proposed in which either ethylene or ACC is a signal involved in specifying the pattern of cell differentiation in the Arabidopsis root epidermis.     

Identity of the Photosystem II reaction center polypeptide

A Photosystem-II (PS-II)-enriched chloroplast submembrane fraction has been subjected to non-denaturing gel-electrophoresis. Two chlorophyll a (Chl a)-binding proteins associated with the core complex were isolated and spectrally characterized. The Chl protein with apparent apoprotein mass of 47 kDa (CP47) displayed a 695 nm fluorescence emission maximum (77 K) and light-induced absorption characteristics indicating the presence of the reaction center Chl, P-680, and its primary electron acceptor, pheophytin. A Chl protein of apparent apoprotein mass of 43 kDa (CP43) displayed a fluorescence emission maximum at 685 nm. We conclude that CP43 serves as an antenna Chl protein and the PS II reaction center is located in CP47.     

The Friesner Herbarium (BUT) of Butler University

The Friesner Herbarium (BUT) of Butler University is a collection of over 100,000 specimens built from the personal herbarium of Ray C. Friesner. He and other botanists at Butler amassed one of the largest and most complete collections of Indiana plants. Active exchange from the 1920’s through the 1940’s increased the holdings of plants from other states. Although the collection does not contain many type specimens, it is rich in vouchers from floristic and ecological studies conducted in the first half of the 20th century and published in the scientific journal,Butler University Botanical Studies.     

Enhanced Mutability Associated with a Temperature-Sensitive Mutant of Vesicular Stomatitis Virus

Temperature-sensitive (ts) mutant tsD1 of vesicular stomatitis virus, New Jersey serotype, is the sole representative of complementation group D. Clones derived from this mutant exhibited three different phenotypes with respect to electrophoretic mobility of the G and N polypeptides of the virion in sodium dodecyl sulfate-polyacrylamide gel. Analysis of non-ts pseudorevertants showed that none of the three phenotypes was associated with the temperature sensitivity of mutant tsD1. Additional phenotypes, some also involving the NS polypeptide, appeared during sequential cloning, indicating that mutations were generated at high frequency during replication of tsD1. Furthermore, mutations altering the electrophoretic mobility of the G, N, NS, and M polypeptides were induced in heterologous viruses multiplying in the same cells as tsD1. These heterologous viruses included another complementing ts mutant of vesicular stomatitis virus New Jersey and ts mutants of vesicular stomatitis virus Indiana and Chandipura virus. Complete or incomplete virions of tsD1 appeared to be equally efficient inducers of mutations in heterologous viruses. Analysis of the progeny of a mixed infection of two complementing ts mutants of vesicular stomatitis virus New Jersey with electrophoretically distinguishable G, N, NS, and M proteins yielded no recombinants and excluded recombination as a factor in the generation of the electrophoretic mobility variants. In vitro translation of total cytoplasmic RNA from BHK cells indicated that post-translational processing was not responsible for the aberrant electrophoretic mobility of the N, NS, and M protein mutants. Aberrant glycosylation could account for three of four G protein mutants, however. Some clones of tsD1 had an N polypeptide which migrated faster in sodium dodecyl sulfate-polyacrylamide gel than did the wild type, suggesting that the polypeptide might be shorter by about 10 amino acids. Determination of the nucleotide sequence to about 200 residues from each terminus of the N gene of one of these clones, a revertant, and the wild-type parent revealed no changes compatible with synthesis of a shorter polypeptide by premature termination or late initiation of translation. The sequence data indicated, however, that the N-protein mutant and its revertant differed from the parental wild type in two of the 399 nucleotides determined. These sequencing results and the phenomenon of enhanced mutability associated with mutant tsD1 reveal that rapid and extensive evolution of the viral genome can occur during the course of normal cytolytic infection of cultured cells.