Life Sciences Commons^™

Investigation Of Arabidopsis Extremophyte Relatives, Schrenkiella Parvula And Eutrema Salsugineum Reveals Different Roads Leading To Salt Stress Tolerance, Kieu-Nga Thi Tran

LSU Doctoral Dissertations

How plants adapt to salt stress has been a central question in plant biology for decades. Yet we have not been able to fully understand the molecular networks and genetic mechanisms underlying this complex trait. Most of the genetic work on salinity stress has focused on understanding salt stress responses in the leading, yet a salt-sensitive model Arabidopsis thaliana. With the recent availability of genomes for wild-relatives of A. thaliana, we can now investigate how naturally salt adapted plants may have evolved modified or novel molecular networks to adapt to salt stress. Therefore, my research utilizes a comparative …

Genetic Structuring And Community Assembly In Neotropical Birds, Oscar Johnson

LSU Doctoral Dissertations

The factors that influence how species form is of fundamental interest to biology. Under the framework of the speciation cycle, the process begins by population subdivision creating structured populations that then diverge until two new species form. Following speciation, however, continued divergence is necessary for these new species to be able to coexist without adverse interactions, known as the transition to secondary sympatry. At this point the speciation cycle is complete and the process can begin anew. Many of the factors influencing these processes remain poorly understood. Here, I explore the factors that influence speciation and community assembly in Neotropical …

Understanding Potassium Toxicity Stress Responses Of The Extremophyte Schrenkiella Parvula Using Systems Biology Approaches, Pramod Pantha

LSU Doctoral Dissertations

Schrenkiella parvula is an extremophyte model closely related to Arabidopsis thaliana and Brassica crops. Its natural habitat includes shores of saline lakes in the Irano-Turanian region. It has adapted to grow in soils rich in multiple salts including Na⁺ and K⁺. I have investigated the genetic basis for high K⁺ tolerance in plants using S. parvula as a stress tolerant model compared to the premier plant model, Arabidopsis thaliana which is highly sensitive to salt stresses using physiological, ionomic, transcriptomic, and metabolomic approaches. Under high K⁺ stress, root system architecture changes significantly compared to control …

Genomic Studies Of Beaf-32 In Drosophila, John Keller Mckowen Iii

LSU Doctoral Dissertations

Compared to humans, the model organism Drosophila melanogaster is particularly gene dense and encodes several insulator binding proteins (IBP) to aid in its genome organization. Our focus of research is a particular IBP, Boundary Element-Associated Factor of 32kD (BEAF). BEAF primarily binds near the promoters of constitutively active housekeeping genes. It is thought to help maintain the active state of these genes by preventing the spread of repressive chromatin. Additionally, the enhancer blocking activity of BEAF is thought to prevent aberrant activation or silencing of genes. BEAF appears to be ubiquitously expressed among cells and tissues, albeit at varying levels. …

Micro- And Macroevolution Of Drab Plumage Color In Birds, Rafael Marcondes

LSU Doctoral Dissertations

I address the evolution of drab bird colors at micro- and macroevolutionary scales. I use as a study system the Furnariida, a clade of >600 Neotropical passerine species that, despite tremendous ecological and morphological diversity, are colored almost exclusively in shades of brown and grey produced by melanin pigments.

In chapters two and three, I took a macroevolutionary approach and showed that (1) plumage colors in the Furnariida evolve at similar rates in a monochromatic clade, males of a dichromatic clade, and females of a dichromatic clade; (2) ventral plumage color evolves faster than dorsal; (3) bird species that occupy …