Environmental and genetic determinants of colony morphology in yeast.

Nutrient stresses trigger a variety of developmental switches in the budding yeast Saccharomyces cerevisiae. One of the least understood of such responses is the development of complex colony morphology, characterized by intricate, organized, and strain-specific patterns of colony growth and architecture. The genetic bases of this phenotype and the key environmental signals involved in its induction have heretofore remained poorly understood. By surveying multiple strain backgrounds and a large number of growth conditions, we show that limitation for fermentable carbon sources coupled with a rich nitrogen source is the primary trigger for the colony morphology response in budding yeast. Using knockout mutants and transposon-mediated mutagenesis, we demonstrate that two key signaling networks regulating this response are the filamentous growth MAP kinase cascade and the Ras-cAMP-PKA pathway. We further show synergistic epistasis between Rim15, a kinase involved in integration of nutrient signals, and other genes in these pathways. Ploidy, mating-type, and genotype-by-environment interactions also appear to play a role in the controlling colony morphology. Our study highlights the high degree of network reuse in this model eukaryote; yeast use the same core signaling pathways in multiple contexts to integrate information about environmental and physiological states and generate diverse developmental outputs.

Evolution of the sex-related locus and genomic features shared in microsporidia and fungi.

BACKGROUND: Microsporidia are obligate intracellular, eukaryotic pathogens that infect a wide range of animals from nematodes to humans, and in some cases, protists. The preponderance of evidence as to the origin of the microsporidia reveals a close relationship with the fungi, either within the kingdom or as a sister group to it. Recent phylogenetic studies and gene order analysis suggest that microsporidia share a particularly close evolutionary relationship with the zygomycetes. METHODOLOGY/PRINCIPAL FINDINGS: Here we expanded this analysis and also examined a putative sex-locus for variability between microsporidian populations. Whole genome inspection reveals a unique syntenic gene pair (RPS9-RPL21) present in the vast majority of fungi and the microsporidians but not in other eukaryotic lineages. Two other unique gene fusions (glutamyl-prolyl tRNA synthetase and ubiquitin-ribosomal subunit S30) that are present in metazoans, choanoflagellates, and filasterean opisthokonts are unfused in the fungi and microsporidians. One locus previously found to be conserved in many microsporidian genomes is similar to the sex locus of zygomycetes in gene order and architecture. Both sex-related and sex loci harbor TPT, HMG, and RNA helicase genes forming a syntenic gene cluster. We sequenced and analyzed the sex-related locus in 11 different Encephalitozoon cuniculi isolates and the sibling species E. intestinalis (3 isolates) and E. hellem (1 isolate). There was no evidence for an idiomorphic sex-related locus in this Encephalitozoon species sample. According to sequence-based phylogenetic analyses, the TPT and RNA helicase genes flanking the HMG genes are paralogous rather than orthologous between zygomycetes and microsporidians. CONCLUSION/SIGNIFICANCE: The unique genomic hallmarks between microsporidia and fungi are independent of sequence based phylogenetic comparisons and further contribute to define the borders of the fungal kingdom and support the classification of microsporidia as unusual derived fungi. And the sex/sex-related loci appear to have been subject to frequent gene conversion and translocations in microsporidia and zygomycetes.

Mount Carmel in the Commune: Promoting the Holy Land in Central Italy in the 13th and 14th Centuries

The Carmelite friars were the last of the major mendicant orders to be established in Italy. Originally an eremitical order, they arrived from the Holy Land in the 1240s, decades after other mendicant orders, such as the Franciscans and Dominicans, had constructed churches and cultivated patrons in the burgeoning urban centers of central Italy. In a religious market already saturated with friars, the Carmelites distinguished themselves by promoting their Holy Land provenance, eremitical values, and by developing an institutional history claiming to be descendants of the Old Testament prophet Elijah. By the end of the 13th century the order had constructed thriving churches and convents and leveraged itself into a prominent position in the religious community. My dissertation analyzes these early Carmelite churches and convents, as well as the friars’ interactions with patrons, civic governments, and the urban space they occupied. Through three primary case studies – the churches and convents of Pisa, Siena and Florence – I examine the Carmelites’ approach to art, architecture, and urban space as the order transformed its mission from one of solitary prayer to one of active ministry.

My central questions are these: To what degree did the Carmelites’ Holy Land provenance inform the art and architecture they created for their central Italian churches? And to what degree was their visual culture instead a reflection of the mendicant norms of the time?

I have sought to analyze the Carmelites at the institutional level, to determine how the order viewed itself and how it wanted its legacy to develop. I then seek to determine how and if the institutional model was utilized in the artistic and architectural production of the individual convents. The understanding of Carmelite art as a promotional tool for the identity of the order is not a new one, however my work is the first to consider deeply the order’s architectural aspirations. I also consider the order’s relationships with its de facto founding saint, the prophet Elijah, and its patron, the Virgin Mary, in a more comprehensive manner that situates the resultant visual culture into the contemporary theological and historical contexts.