Transcription Factors Mat2 and Znf2 Operate Cellular Circuits Orchestrating Opposite- and Same-Sex Mating in Cryptococcus neoformans

Cryptococcus neoformans is a human fungal pathogen that undergoes a dimorphic transition from a unicellular yeast to multicellular hyphae during opposite sex (mating) and unisexual reproduction (same-sex mating). Opposite- and same-sex mating are induced by similar environmental conditions and involve many shared components, including the conserved pheromone sensing Cpk1 MAPK signal transduction cascade that governs the dimorphic switch in C. neoformans. However, the homeodomain cell identity proteins Sxi1α/Sxi2a encoded by the mating type locus that are essential for completion of sexual reproduction following cell–cell fusion during opposite-sex mating are dispensable for same-sex mating. Therefore, identification of downstream targets of the Cpk1 MAPK pathway holds the key to understanding molecular mechanisms governing the two distinct developmental fates. Thus far, homology-based approaches failed to identify downstream transcription factors which may therefore be species-specific. Here, we applied insertional mutagenesis via Agrobacterium-mediated transformation and transcription analysis using whole genome microarrays to identify factors involved in C. neoformans differentiation. Two transcription factors, Mat2 and Znf2, were identified as key regulators of hyphal growth during same- and opposite-sex mating. Mat2 is an HMG domain factor, and Znf2 is a zinc finger protein; neither is encoded by the mating type locus. Genetic, phenotypic, and transcriptional analyses of Mat2 and Znf2 provide evidence that Mat2 is a downstream transcription factor of the Cpk1 MAPK pathway whereas Znf2 functions as a more terminal hyphal morphogenesis determinant. Although the components of the MAPK pathway including Mat2 are not required for virulence in animal models, Znf2, as a hyphal morphology determinant, is a negative regulator of virulence. Further characterization of these elements and their target circuits will reveal genes controlling biological processes central to fungal development and virulence

Combined uses of supervised classification and Normalized Difference Vegetation Index techniques to monitor land degradation in the Saloum saline estuary system

peer reviewedSaltwater contamination constitutes a serious problem in Saloumestuary, due to the intermittent and reverse tide flows of the Saloum River. This phenomenon is caused by the runoff deficit, which forces the advance of saltwater 60 km upstream, contaminating surface water and thus causing the degradation of biodiversity and large areas of agricultural soils in this region. The present study aims to evaluate the consequences of saltwater contamination in the last three decades in this estuary by assessing the land-cover dynamics. Thus, latter consists of tracking the landscape-changing process over time to identify land-cover transitions. These transitions are closely related to the ecosystem-setting condition and can be used to assess the combined impacts of both natural and human-induced phenomena over a given period of time. In this study, special attention was given to mangrove degradation and to temporal progression of the salty barren soils locally called ‘‘tan’’. The loss of mangrove areas to tan and the general increase in salty barren soil areas can reflect the increase in the level of salinization in the study area over the time period under consideration. To fulfill this objective, four Landsat satellite images from the same season in the years 1984, 1992, 1999, and 2010 were used to infer time series land-use and land-cover maps of the Saloumestuary area. In addition to satellite imagery, rainfall records were used to evaluate climatic variation in terms of high-to-low precipitation during the time span considered. Spectral analysis indicated that from 1984 to 2010, mangroves and savanna/ rain-fed agriculture are converted to ‘‘tan’’ (denuded and salty soils). In addition, these results showed that significant changes in land use/land cover occur within the whole estuary system and reflecting therefore environmental degradation, such as land desertification and salinization, and vegetation degradation which reflect the advanced of salinit

Automatic Change Detection from High-Resolution Satellite Imagery

Change detection using remote sensing data is one of the most essential processing steps for monitoring urban and forest areas. And it provides an invaluable tool for archaeological sites in times of war or natural disasters. However, until now the visual interpretation is still the main technique in analyzing changes from these images. In this chapter, the state of the art of the change detection on archaeology applications and the latest change detection techniques in 2D and 3D are introduced