Efficacy of a Novel Molecular Tool in Silencing Arabidopsis Genes

RNA interference (RNAi), a pathway capable of silencing genes, has until recently only been achievable in the laboratory by the use of one method, expression of inverted repeat sequences of DNA. These constructs generate a double-stranded RNA, which in turn induce post-transcriptional silencing of other genes that bear sequence homology with the transgene. This approach of targeted gene silencing is extremely useful for studying the function of genes and engineering new traits in both plants and animals. It has recently been discovered that a transgene lacking the polyadenylation signal, called a truncated transgene, is also capable of inducing RNAi in plant cells. This technique was used in efficiently silencing two genes of Arabidopsis thaliana, the Phytochrome A (PHYA) and Phytochrome B (PHY B) genes; however, the effectiveness of this method on a broader range of genes is unknown. The purpose of this study is to analyze the effect of truncated-transgene expression on the homologous native genes in the Arabidopsis genome. More specifically, the rate of silencing of three genes, Variegated 2 (VAR2), Brassinosteroid Insensitive 1 (BRI1) and Apetala 1 (AP1) due to the expression of truncated VAR2, BRI1, and AP1 transgenes, respectively, in Arabidopsis thaliana was examined. This experiment provided important data for assessing the efficacy of truncated transgene based gene silencing system for plants

Conventional versus giant basal cell carcinoma, a review of 57 Cases: Histologic differences contributing to excessive growth

Background: Giant basal cell carcinoma (GBCC) is defined as a basal cell carcinoma (BCC) exceeding 5 cm in size. While these tumors impart significant morbidity due to local tissue destruction and have a higher rate of metastatic disease than their conventional (smaller) counterparts, reasons for their large size remain unclear. While theories relating to neglect or faster growth rate are often invoked; to date, there has not been a comprehensive evaluation of the histologic features of these large tumors that may contribute to their size. Methods: Histologic features of GBCCs (n = 29) were evaluated and compared to those of conventional BCC (n = 28). Available clinical demographic data were also reviewed. Results: GBCCs, in addition to overall larger size, more often were thicker, displayed ulceration, and showed a more infiltrative growth pattern than their conventional counterparts. These rare tumors also displayed an insignificant increased propensity for a brisk host immune response, and the infiltrate significantly more often included clusters of plasma cells. Conclusions: Most histologic features seen in GBCCs likely reflect their large size. Histologic features alone are unlikely to explain the size of these rare tumors. The possibility of an altered host immune response contributing to the growth of these tumors requires further investigation

Cretaceous fire in Australia: A review with new geochemical evidence, and relevance to the rise of the angiosperms

Much of the Australian flora has high flammability. It is therefore of interest whether burning was a feature in the Cretaceous, the geological period in which angiosperms rose to dominance, and in which fossil and molecular evidence suggests the presence of lineages now prominent in regularly burnt habitats. Determining the extent of fire in the Australian Cretaceous is limited by a paucity of surface exposures of strata, and of published reports of definite charcoal from exploration cores. Nevertheless, charcoalified tissues occur much more widely than is currently reported in the international literature, and there are also numerous references to inertinite macerals in Australian Cretaceous coals. Combustion-related hydrocarbons can also be detected in ancient sediments using organic geochemical methods, and we demonstrate the potential of this approach here. Overall, the available evidence is in concert with that from elsewhere on Earth: fire was apparently widespread in the Australian Cretaceous, and can reasonably be invoked as a force that in fluenced the evolution of modern Australian environments. Just as in extant open, nutrient-limited regions, proteaceous lineages seem to have been important in burnt, open habitats in the Late Cretaceous, perhaps retaining dominance of such niches for > 70 million years. However, there is so far no fossil evidence for the Cretaceous presence of Eucalyptus, the principal tree genus of modern Australian fire-prone vegetation