Henipaviruses and lyssaviruses target nucleolar treacle protein and regulate ribosomal RNA synthesis

The nucleolus is a common target of viruses and viral proteins, but for many viruses the functional outcomes and significance of this targeting remains unresolved. Recently, the first intranucleolar function of a protein of a cytoplasmically-replicating negative-sense RNA virus (NSV) was identified, with the finding that the matrix (M) protein of Hendra virus (HeV) (genus Henipavirus, family Paramyxoviridae) interacts with Treacle protein within nucleolar subcompartments and mimics a cellular mechanism of the nucleolar DNA-damage response (DDR) to suppress ribosomal RNA (rRNA) synthesis. Whether other viruses utilise this mechanism has not been examined. We report that sub-nucleolar Treacle targeting and modulation is conserved between M proteins of multiple Henipaviruses, including Nipah virus and other potentially zoonotic viruses. Furthermore, this function is also evident for P3 protein of rabies virus, the prototype virus of a different RNA virus family (Rhabdoviridae), with Treacle depletion in cells also found to impact virus production. These data indicate that unrelated proteins of viruses from different families have independently developed nucleolar/Treacle targeting function, but that modulation of Treacle has distinct effects on infection. Thus, subversion of Treacle may be an important process in infection by diverse NSVs, and so could provide novel targets for antiviral approaches with broad specificity.     

Isolation of signaling mutants of tomato (Lycopersicon esculentum)

As a first step towards developing a genetic system for investigating signaling processes in plants, we have developed a screen for signaling mutants deficient in a wound response. We have isolated two mutants of tomato that lack detectable production of proteinase inhibitors induced systemically in leaves by wounding. The mutants are deficient in the induction of both proteinase Inhibitor I and proteinase Inhibitor II but can be induced to respond at near wild-type levels by methyl jasmonate, a known elicitor of inhibitor production in tomato. While completely deficient in systemic production of proteinase inhibitors, both mutants produce some proteinase inhibitor in wounded leaves. This evidence suggests the existence of two signaling pathways, one local and one systemic, that regulate the induction of proteinase inhibitor snythesis in response to wounding.     

FUNCTIONAL DIOECY AND ANDROMONOECY IN SOLANUM

Field and laboratory studies of 19 diclinous species endemic to Australia help to clarify the nature and evolution of andromonoecy, androdioecy, and dioecy in the genus Solanum. Ten species are andromonoecious; typically these species bear inflorescences with a single, large basal hermaphroditic flower and 12–60 distal, smaller staminate flowers. We suggest that the andromonoecious condition was derived from hermaphroditic-flowered ancestors in part by hemisterilization of flowers but largely by addition of staminate flowers. The resultant larger inflorescences are hypothesized to serve both to attract and to entrain pollinators, yielding more or higher-quality seed set in hermaphroditic flowers and/or greater dispersion of pollen from staminate flowers. We suggest that andromonoecy may also serve to reduce selling. Nine other species are morphologically androdioecious but functionally dioecious. In these species, staminate flowers, like those of the andromonoecious species, bear anthers with copious tricolporate pollen and a highly reduced gynoecium. The morphologically hermaphroditic flowers are functionally pistillate and borne singly in inflorescences, and they bear anthers with inaperturate pollen. The inaperturate pollen, although viable, never germinates and is hypothesized to be retained in pistillate flowers as a reward to pollinators in the nectarless Solanum flowers. All other species of Solanum studied with pollen dimorphism in which one pollen morph is inaperturate are also best treated as functionally dioecious. We conclude that there is no evidence for androdioecy in Solanum. A review of other families suggests that there is little support for this unusual breeding system in any other angiosperm group either. Preliminary analyses suggest that andromonoecy and dioecy are polyphyletic in Solanum. Furthermore, dioecy is as likely to have arisen from hermaphroditic as from andromonoecious ancestors.     

MOLECULAR HETEROCHRONIES AND HETEROTOPIES IN EARLY ECHINOID DEVELOPMENT

By comparing the spatial and temporal distribution of three proteins during early development in seven echinoid species, we demonstrate that both heterochronies and heterotopies in gene-product expression have accompanied the radiation of post-Paleozoic echinoids. All three proteins examined showed significant alterations in time of expression, site of expression, or both. These molecular heterochronies and heterotopies indicate that early development is not necessarily as evolutionarily conservative as morphology of embryos alone would suggest. Evolutionary alterations in early development may be more common than is generally assumed.     

Hepatic Gluconeogenesis and the Activity of PDH in Individual Tissues of GTG-Obese Mice Following Adrenalectomy

Adrenalectomy (ADX) lowers circulating glucose levels in animal models of non-insulin dependent diabetes (NIDDM) and obesity. To investigate the role of hepatic glucose production (HGP) and tissue glucose oxidation in the improvement in glucose tolerance, hepatocyte gluconeogenesis and the activity of pyruvate dehydrogenase (PDH) were examined in different tissues of gold thioglucose (GTG) obese mice 2 weeks after ADX or sham ADX. GTG-obese mice which had undergone ADX weighed significantly less than their adrenal intact counterparts (GTG ADX: 37.5 ± 0.7g; GTG: 44.1 ± 0.4g; p<0.05), and demonstrated lower serum glucose (GTG ADX: 22.5 ± 1.6 mmol/L; GTG: 29.4 ± 1.9 mmol/L; p<0.05) and serum insulin levels (GTG ADX: 76 ± 10μ.U/mL; GTG: 470 ± 63μU/mL; p<0.05). Lactate conversion to glucose by hepatocytes isolated from ADX GTG mice was significantly reduced compared with that of hepatocytes from GTG mice (GTG ADX: 125 ± 10 nmol glucose/10⁶ cells; GTG: 403 ± 65 nmol glucose/10⁶ cells; p<0.05). ADX also significantly reduced both the glycogen (GTG ADX: 165 ± 27 μmol/liver; GTG: 614 ± 60 pmol/Iiver; p<0.05) and fatty acid content (GTG ADX: 101 ± 9 mg fatty acid/g liver; GTG: 404 ± 40 mg fatty acid/g liver; p<0.05) of the liver of GTG-obese mice. ADX of GTG-obese mice reduced PDH activity by varying degrees in all tissues, except quadriceps muscle. These observations are consistent with an ADX induced decrease in hepatic lipid stores removing fatty acid-induced increases in gluconeogenesis and increased peripheral availability of fatty acids inhibiting PDH activity via the glucose/fatty acid cycle. It is also evident that the improvement in glucose tolerance which accompanies ADX of GTG-obese mice is not due to increased PDH activity resulting in enhanced peripheral glucose oxidation. Instead, it is more likely that reduced blood glucose levels after ADX of GTG-obese mice are the result of decreased gluconeogenesis in the liver.     

Detection and identification of ferricrocin produced by ectendomycorrhizal fungi in the genusWilcoxina

The ectendomycorrhizal fungiWilcoxina mikolae isolates CSY-14 and RMD-947 andW. rehmii isolate CSY-85 were grown in pure culture under iron-limiting conditions. All three isolates tested positive for siderophore formation using both the ferric perchlorate assay and a sensitive HPLC iron-binding assay. A peptide siderophore was isolated from the culture medium by HPLC and shown to contain the amino acids serine, glycine and ornithine in a 1:2:3 ratio. This siderophore was identified as ferricrocin on the basis of electrospray mass spectroscopy and its co-chromatography in two different HPLC systems with ferricrocin isolated fromAspergillus fumigatus. Ferricrocin was the only siderophore isolated from theseWilcoxina cultures. This is the first report of siderophore formation by ectendomycorrhizal fungi.