Arabidopsis microarrays identify conserved and differentially expressed genes involved in shoot growth and development from distantly related plant species

Expressed sequence tags (EST)-based microarrays are powerful tools for gene discovery and signal transduction studies in a small number of well-characterized species. To explore the usefulness of this technique for poorly characterized species, we have hybridized the 11,522-element Arabidopsis microarrays with labeled cDNAs from mature leaf and shoot apices from several different species. Expression of 23 to 47% of the genes on the array was detected, demonstrating that a large number of genes from distantly related species can be surveyed on Arabidopsis arrays. Differential expression of genes with known functions was indicative of the physiological state of the tissues tested. Genes involved in cell division, stress responses, and development were conserved and expressed preferentially in growing shoots.     

Molecular analysis of signals controlling dormancy and growth in underground adventitious buds of leafy spurge

Dormancy and subsequent regrowth of adventitious buds is a critical physiological process for many perennial plants. We have used the expression of hormone and cell cycle-responsive genes as markers to follow this process in leafy spurge (Euphorbia esula). In conjunction with earlier studies, we show that loss of mature leaves results in decreased sugar levels and increased gibberellin perception in underground adventitious buds. Gibberellin is sufficient for induction of S phase-specific but not M phase-specific gene expression. Loss of both apical and axillary buds or inhibition of polar auxin transport did not result in induction of S phase- or M phase-specific gene expression. Loss of polar auxin transport was necessary for continuation of the cell cycle and further bud development if the S phase was previously initiated.     

Mechanistic studies of the plasma membrane block to polyspermy in mouse eggs

The mechanisms responsible for the plasma membrane associated block to polyspermy in mouse eggs were studied. Reinsemination experiments using zona-free eggs indicated that, after fertilization, the egg plasma membrane is altered such that sperm binding to the egg plasma membrane is blocked, except in the region of the second polar body. Activation of the egg with either ethanol or strontium chloride did not result in a block to polyspermic penetration, as artificially activated eggs displayed identical penetration levels as to nonactivated control eggs. The penetrability of activated eggs was not altered by the presence or absence of the zona pellucida during activation. Lectin staining for egg cortical granule material indicated that activation did cause cortical granule exocytosis; however, activated eggs remained penetrable. These data support the following conclusions: (1) an alteration in the ability of the egg plasma membrane to allow sperm adherence accounts for the block to polyspermy; (2) establishment of the plasma membrane block to polyspermy is sperm dependent, since artificial egg activation does not result in a block response; (3) the contents of the egg's cortical granules do not play a role in the establishment of the plasmalemma block response. © 1993 Wiley-Liss, Inc.     

Hormone regulation of cellular metabolism: Interplay of membrane transport and consecutive enzymic reaction

The regulatory effect of hormones on a steady-state process that consists of the mediated transport of a substrate across a membrane and a consecutive enzymic reaction is examined theoretically. The regulation of such a process depends not only on the effect of the hormone on the transport system, but also on the kinetic parameters of the reaction. The rate of metabolism can both increase and decrease due to a hormonal increase in the transport capacity, the affinity of the carrier to the substrate or the amount of energy involved, although the rate of mediated transport per se is always enhanced by such effects. Substrate inhibition of the enzyme can lead to multiple steady states and, thus, amplify hormone action. The quantitative results are believed to give insight into the hormonal regulation of both cellular uptake and intracellular metabolism.     

Interpretation of isolated agenesis of the pituitary.

Cholesterol synthesis inhibitors administered to rats caused more or less complete forms of the holoprosencephalic syndrome, consisting of severe abnormalities of the brain, sense organs and pituitary. The absence of the pituitary was also observed in fetuses without externally visible cephalic abnormalities. These observations suggest that the isolated absence of the pituitary is the lesser form of the holoprosencephalic syndrome. This interpretation is also valid for cases of isolated absence of the pituitary observed in humans.     

Co-metabolism of fluorobenzoates by natural microbial populations.

Co-metabolic degradation of monofluorobenzoates was carried out by a mixed soil population in a basal salts medium. The monofluorobenzoates did not support growth of microorganisms but were shown to be subject to ring cleavage as a result of microbial activity. Rate of ring cleavage was increased by use of the co-substrate enrichment technique using glucose as the co-substrate. Results indicate that the monofluorobenzoates were subject to an initial co-metabolic attack with glucose, providing the energy necessary for co-metabolism to proceed to a point where complete metabolism became possible.     

Genetic analysis of simian virus 40 from brains and kidneys of macaque monkeys.

Simian virus 40 (SV40) was isolated from the brains of three rhesus monkeys and the kidneys of two other rhesus monkeys with simian immunodeficiency virus-induced immunodeficiency. A striking feature of these five cases was the tissue specificity of the SV40 replication. SV40 was also isolated from the kidney of a Taiwanese rock macaque with immunodeficiency probably caused by type D retrovirus infection. Multiple full-length clones were derived from all six fresh SV40 isolates, and two separate regions of their genomes were sequenced: the origin (ori)-enhancer region and the coding region for the carboxy terminus of T antigen (T-ag). None of the 23 clones analyzed had two 72-bp enhancer elements as are present in the commonly used laboratory strain 776 of SV40; 22 of these 23 clones were identical in their ori-enhancer sequences, and these had only a single 72-bp enhancer element. We found no evidence for differences in ori-enhancer sequences associated with tissue-specific SV40 replication. The T-ag coding sequence that was analyzed was identical in all clones from kidney. However, significant variation was observed in the carboxy-terminal region of T-ag in SV40 isolated from brain tissues. This sequence variation was located in a region previously reported to be responsible for SV40 host range in cultured cell lines. Thus, SV40 appears to be an opportunistic pathogen in the setting of simian immunodeficiency virus-induced immunodeficiency, similarly to JC virus in human immunodeficiency virus-infected humans, the enhancer sequence organization generally attributed to SV40 is not representative of natural SV40 isolates, and sequence variation near the carboxy terminus of T-ag may play a role in tissue-specific replication of SV40.     

Biological activity of paramyxovirus fusion proteins: factors influencing formation of syncytia.

The fusion (F) and hemagglutinin-neuraminidase (HN) glycoproteins of the paramyxovirus simian virus 5 (SV5) were expressed individually or coexpressed in CV-1 cells by using SV40-based vectors and recombinant vaccinia viruses. The extent of detectable fusion in a syncytium formation assay was found to be affected by the expression system used. In addition, when HN was coexpressed with F, it was found that the expression vector system influenced the contribution of HN in forming syncytia. The abilities of the SV5, human parainfluenza virus type 3, and Newcastle disease virus F glycoproteins to cause fusion, when expressed alone or coexpressed with HN, were directly compared by using the SV40-based vector system in CV-1 cells. The F proteins exhibited various degrees of fusion activity independent of HN expression, but the formation of syncytia could be enhanced to different extents by the coexpression of the homotypic HN protein.