Project description:Biological soil crusts (BSCs) are cyanobacteria-dominated microbial communities that cover extensive portions of the world’s arid and semi-arid deserts. The infrequent periods of hydration are often too short to allow for dormancy strategies based on sporulation; consequently, survival is based on the unique capabilities of vegetative cells to resuscitate from and re-enter a stress resistant dormant state, one of which is migration within the crust layers in response to hydration. In this study, we sought to characterize the events that govern the emergence of the dominant cyanobacterium from dormancy, its subsequent growth, and the events triggered by re-desiccation and a transition back to dormant state. We performed a 48 hour laboratory wetting experiment of a desert BSC and tracked the response of Microcoleus vaginatus using a whole genome transcriptional time-course including night/day periods. This allowed the identification of genes with a diel expression pattern, genes involved uniquely in the signaling after hydration and those that contribute primarily to desiccation preparation. Desert BSC samples collected from Moab, UT, were hydrated over a period of 48 hours followed by drying induced by removal of water. At periodic times soil samples were harvested and used for RNA extraction and whole genome expression analysis using an expression array representing genes from two strains of M. vaginatus (PCC 9802 and FGP-2)
Project description:Three-day metatranscriptome of surface gravel plain soils from the Central Namib Desert. Samples were collected at four times (6:00, 12:00, 18:00 and 24:00h) on each day (n=12). rRNA-depleted RNA was used to construct stranded libraries with the ScriptSeq v2 complete kit (Epicentre) adding unique barcodes in TruSeq adapters (ScriptSeq Index PCR primers, set 1, Epicentre). Libraries were single-end sequenced in a NextSeq 500 v2 sequencer, with read length of 75bp.
Project description:Desert microbial communities live in a pulsed ecosystem shaped by isolated and rare precipitation events. The Namib desert is one of the oldest continuously hyperarid ecosystems on Earth. In this study, surface microbial communities of open soils (without sheltering features like rocks, vegetation or biological soil crusts) are analysed. We designed an artificial rainfall experiment where a 7x7 (3.5 x 3.5 m) plot remained dry while an adjacent one received a 30 mm simulated rain. Samples were taken randomly in parallel from both plots at 10 min, 1 h, 3 h, 7 h, 24 h and 7 days after the watering moment. Duplicate libraries were generated from total (rRNA depleted) RNA and sequenced 2x150 bp in an Illumina Hiseq 4000 instrument.
Project description:Biological soil crusts (BSCs) are cyanobacteria-dominated microbial communities that cover extensive portions of the world’s arid and semi-arid deserts. The infrequent periods of hydration are often too short to allow for dormancy strategies based on sporulation; consequently, survival is based on the unique capabilities of vegetative cells to resuscitate from and re-enter a stress resistant dormant state, one of which is migration within the crust layers in response to hydration. In this study, we sought to characterize the events that govern the emergence of the dominant cyanobacterium from dormancy, its subsequent growth, and the events triggered by re-desiccation and a transition back to dormant state. We performed a 48 hour laboratory wetting experiment of a desert BSC and tracked the response of Microcoleus vaginatus using a whole genome transcriptional time-course including night/day periods. This allowed the identification of genes with a diel expression pattern, genes involved uniquely in the signaling after hydration and those that contribute primarily to desiccation preparation.
Project description:This study examined fungal diversity and composition in conventional (CM) and desert farming (DE) systems in Oman. Fungal diversity in the rhizosphere of tomato was assessed using 454-pyrosequencing and culture-based techniques. Both techniques produced variable results in terms of fungal diversity, with 25% of the fungal classes shared between the two techniques. In addition, pyrosequencing recovered more taxa compared to direct plating. These findings could be attributed to the ability of pyrosequencing to recover taxa that cannot grow or are slow growing on culture media. Both techniques showed that fungal diversity in the conventional farm was comparable to that in the desert farm. However, the composition of fungal classes and taxa in the two farming systems were different. Pyrosequencing revealed that Microsporidetes and Dothideomycetes are the two most common fungal classes in CM and DE, respectively. However, the culture-based technique revealed that Eurotiomycetes was the most abundant class in both farming systems and some classes, such as Microsporidetes, were not detected by the culture-based technique. Although some plant pathogens (e.g., Pythium or Fusarium) were detected in the rhizosphere of tomato, the majority of fungal species in the rhizosphere of tomato were saprophytes. Our study shows that the cultivation system may have an impact on fungal diversity. The factors which affected fungal diversity in both farms are discussed.
Project description:Gene deserts spanning more than 500kb of non-protein coding genomic sequence are considered evolutionarily ancient and stable and are enriched in the vicinity of developmental regulator genes (Ovcharenko 2005). These extensive genomic regions typically harbor numerous conserved elements with predicted gene regulatory potential pointing to critical tissue-specific functions during development. Nevertheless, the biological necessity and underlying funtional enhancer landscapes of most gene deserts near developmental transcription factors (TFs) remain unknown, and it is unclear how precise pleiotropic expression patterns emerge from gene desert sequence. Here, we investigated the cis-regulatory architecture and function of a gene desert flanking the mouse Shox2 transcriptional regulator which itself is essential for embryonic limb, craniofacial, and cardiac pacemaker development. By combining epigenomic enhancer prediction, transgenic reporter validation and region-specific chromatin capture (C-HiC), we define the embryonic in vivo enhancer landscape and chromatin topology of the Shox2 gene desert. Targeted and context-specific genomic deletions uncover the gene desert not only as a regulator of embryonic survival through enhancer-mediated control of cardiac Shox2 expression, but also link distinct subsets of tissue-specific gene desert enhancers to the regulation of craniofacial patterning and proximal limb development. Our results hence identify the Shox2 gene desert as a fundamental genomic unit indispensable for pleiotropic patterning, robust organ morphogenesis and embryonic development progression by serving as a dynamic hub for tissue-specific developmental enhancers.
Project description:Gene deserts spanning more than 500kb of non-protein coding genomic sequence are considered evolutionarily ancient and stable and are enriched in the vicinity of developmental regulator genes (Ovcharenko 2005). These extensive genomic regions typically harbor numerous conserved elements with predicted gene regulatory potential pointing to critical tissue-specific functions during development. Nevertheless, the biological necessity and underlying funtional enhancer landscapes of most gene deserts near developmental transcription factors (TFs) remain unknown, and it is unclear how precise pleiotropic expression patterns emerge from gene desert sequence. Here, we investigated the cis-regulatory architecture and function of a gene desert flanking the mouse Shox2 transcriptional regulator which itself is essential for embryonic limb, craniofacial, and cardiac pacemaker development. By combining epigenomic enhancer prediction, transgenic reporter validation and region-specific chromatin capture (C-HiC), we define the embryonic in vivo enhancer landscape and chromatin topology of the Shox2 gene desert. Targeted and context-specific genomic deletions uncover the gene desert not only as a regulator of embryonic survival through enhancer-mediated control of cardiac Shox2 expression, but also link distinct subsets of tissue-specific gene desert enhancers to the regulation of craniofacial patterning and proximal limb development. Our results hence identify the Shox2 gene desert as a fundamental genomic unit indispensable for pleiotropic patterning, robust organ morphogenesis and embryonic development progression by serving as a dynamic hub for tissue-specific developmental enhancers.
Project description:Gene deserts spanning more than 500kb of non-protein coding genomic sequence are considered evolutionarily ancient and stable and are enriched in the vicinity of developmental regulator genes (Ovcharenko 2005). These extensive genomic regions typically harbor numerous conserved elements with predicted gene regulatory potential pointing to critical tissue-specific functions during development. Nevertheless, the biological necessity and underlying funtional enhancer landscapes of most gene deserts near developmental transcription factors (TFs) remain unknown, and it is unclear how precise pleiotropic expression patterns emerge from gene desert sequence. Here, we investigated the cis-regulatory architecture and function of a gene desert flanking the mouse Shox2 transcriptional regulator which itself is essential for embryonic limb, craniofacial, and cardiac pacemaker development. By combining epigenomic enhancer prediction, transgenic reporter validation and region-specific chromatin capture (C-HiC), we define the embryonic in vivo enhancer landscape and chromatin topology of the Shox2 gene desert. Targeted and context-specific genomic deletions uncover the gene desert not only as a regulator of embryonic survival through enhancer-mediated control of cardiac Shox2 expression, but also link distinct subsets of tissue-specific gene desert enhancers to the regulation of craniofacial patterning and proximal limb development. Our results hence identify the Shox2 gene desert as a fundamental genomic unit indispensable for pleiotropic patterning, robust organ morphogenesis and embryonic development progression by serving as a dynamic hub for tissue-specific developmental enhancers.