2021 Speakers

Dr. Becky Bart- Donald Danforth Plant Science Center

Dr. Becky Bart

Title: Editing the genome and epigenome of cassava to promote disease resistance

Abstract: Cassava (Manihot esculenta) is an important food security crop in much of the world. Although cassava is prized as a highly productive crop even when grown without irrigation or fertilizer, it suffers from several microbial pathogens that can significantly impact yield. In this talk, I will cover two of the most important diseases of cassava: Cassava Brown Streak Disease caused by an RNA viral pathogen, and Cassava Bacterial Blight, caused by Xanthomonas. In both cases, we have identified important host susceptibility genes (S genes). S genes are encoded in the host genome and are required by the pathogen to complete its lifecycle. I will describe our work on exploring the biology of these unique pathosystems. Further, I will share recent data using various genome and epigenome editing tools to prevent the pathogens from accessing their cognate S genes and how, generally, these approaches can be used to promote host resistance. 

Biography: Becky competed her undergraduate education at Reed College in Portland Oregon before pursuing her doctoral research in the Plant Pathology Department at UC Davis. There she worked with Prof. Pamela Ronald to elucidate genetic components of the rice innate immune response. Becky then worked as a USDA-NIFA postdoctoral scholar in Prof. Brian Staskawicz’s laboratory at UC Berkeley to further understand the molecular and genetic interaction between the important food crop, cassava, and its major bacterial pathogen Xanthomonas axonopodis pv. manihotis. Becky began her own laboratory at the Donald Danforth Plant Science Center in the Fall of 2013. Dr. Bart’s research program occupies the unique and important space between ‘mystery driven’ scientific pursuits and impactful translation of science into solutions for farmers. Specifically, she works on understanding the interactions between plants, microbes and the environment. This includes developing and deploying novel genetic methods to protect plants from pathogens and cultivating associations with beneficial microbes. Her work is bolstered by cutting edge technologies including modeling, genomics, high throughput phenotyping and gene editing.

Dr. Phillip Cleves- Carnegie Institute for Science

Dr. Phillip Cleves

Title: Using Transcriptomics and Reverse Genetics to Understand Mechanisms of Cnidarian-dinoflagellate Bleaching

Abstract: The symbiosis between corals and dinoflagellate algae is essential to the energetic requirements of coral-reef ecosystems. However, coral reefs are in danger due to elevated ocean temperatures and other stresses that lead to the breakdown of this symbiosis and coral “bleaching”. Despite the importance of coral reefs, the molecular basis of how corals maintain a healthy symbiosis and avoid bleaching is poorly understood, in part because of the lack of a tractable genetic model system. The small anemone Aiptasia is symbiotic with algalstrains like those in reef-building corals but has many experimental advantages, making it an attractive laboratory model for cnidarian symbiosis.  To explore the transcriptional basis of heat-induced bleaching, we used RNAseq to identify genes that are differentially expressed during a time course of heat stress of symbiotic and aposymbiotic Aiptasiastrains. We observed a strong upregulation of hundreds of genes at times long before bleaching begins in symbiotic anemones. The putative promoters of these early stress-response genes are enriched for binding sites for the NFkB and HSF1 transcription factors, suggesting that many of these genes share core transcriptional control. The overall expression patterns were similar between the symbiotic and aposymbiotic anemones, indicating that many of the expression changes are not specific to the presence of the algae. Nonetheless, reducing HSF1 activity with a pharmacological inhibitor resulted in more severe bleaching, suggesting that this symbiont-independent stress response is protective against bleaching.

Genetic tools are needed to allow rigorous functional testing of the roles of candidate genes in symbiosis and bleaching. Recently, we have developed methods for knocking down and overexpressing genes of interest in Aiptasia. Meanwhile, we have successfully used the CRISPR/Cas9 technology to create genetic changes in embryos of the coral Acropora millepora. We used this technology to knock out HSF1 and demonstrated its role in coral heat tolerance.  Through the establishment of both gain-of-function and loss-of-function methods in both Aiptasia and corals, it will be possible to exploit the year-round spawning of Aiptasia to perform initial tests of gene function in cnidarian-algal symbiosis and then further test the discoveries made using similar technologies in corals.

Biography: Dr. Phillip Cleves received a B.S. in Biology from the University of Arkansas, Fayetteville, and a Ph.D. in Molecular and Cell Biology from the University of California, Berkeley. For his Ph.D., he studied the molecular genetic basis of morphological evolution in stickleback fish. After his Ph.D., he continued to his postdoctoral work studying coral symbiosis at Stanford University. There, he has applied next-generation sequencing and genome editing tools to study the genetic networks that orchestrate this symbiosis in corals. These technological advancements allow for the dissection of coral gene function for the first time.  In 2021, Phillip started his own lab studying the cellular basis of coral symbiosis and bleaching at the Carnegie Institute for Science – Department of Embryology and Johns Hopkins University – Department of Biology.  

Dr. Elizabeth Maga- UC Davis

Dr. Elizabeth A. Maga

Title: Translating the use of lysozyme-rich milk from transgenic goats to fight diarrheal illnesses

Abstract: Genetic engineering as applied to animal agriculture has the potential to benefit both animal and human health. For instance, human milk contains several factors that promote the growth of beneficial gut bacteria that help fight infection and maintain health; however, these factors are lacking in the milk of dairy animals. By producing these key antimicrobial components as part of the milk of farm animals, there is the potential to supply these health-promoting factors to human consumers throughout their lifetime. We have genetically engineered dairy goats to make one of these important antimicrobial factors, human lysozyme (hLZ) in their milk. Due to the purported role of human milk on gut microbiota formation, a source of milk rich in lysozyme could shift the microbial population of the gut during milk consumption to those microbes associated with beneficial activities for the host. Over the past 15 years, we have been using the pig as a human-relevant animal model to test the ability of hLZ goat milk to treat and prevent diarrhea which remains a leading cause of death of children under the age of five worldwide. Consumption of lysozyme-rich milk results in the modulation of gut microbiota in healthy, malnourished and E. coli-challenged pigs, promotes a healthier intestinal epithelium and can both resolve and prevent the symptoms of E. coli-induced diarrhea. These studies are paving the way for mechanistic studies on the role of gut microbiota modulation on intestinal and overall health and translational studies on the use of lysozyme-rich milk to treat and prevent diarrheal and intestinal diseases.

Biography: Dr. Elizabeth Maga is an Associate Professor of Applied Molecular Genetics in the Department of Animal Science at the University of California, Davis. She has a BS in Chemical Engineering from Colorado State University (1988) and a PhD in Food Science and Technology from UC Davis (1994). Her research focuses on applying biotechnology to animal agriculture as a tool to improve animal and human health. Her current work is directed at translating the use of lysozyme-rich milk from genetically engineered goats to fight intestinal diseases and the generation of gene edited pigs for agricultural and biomedical purposes. Dr. Maga has taught courses in molecular biology, introductory animal science and advances in animal biotechnology as well as lactation and integrative animal biology at UC Davis. She has received multiple federally-funded (USDA-NIFA) research grants to study the impact of transgene presence and expression on the biology of the transgenic animal and a Grand Challenges Explorations Award from the Bill and Melinda Gates Foundation to study the effects of milk on malnutrition using a pig model.

Dr. Arnaud Martin- George Washington University

Dr. Arnaud Martin

Title: Do butterflies dream of genetic tattoos? Exploring color pattern evolution using CRISPR

Abstract: Understanding the generative mechanisms of morphological diversification requires the routine manipulation of genomes in a comparative context. I will present how current work using CRISPR mutagenesis illuminates how the wing color patterns of butterflies have radiated into an iconic example of biodiversity. CRISPR has indeed been a true revolution allowing the routine interrogation of gene function in insects that were previously difficult to manipulate in the lab. Gene knock-outs in butterflies reveal spectacular phenotypes that modify pattern shapes and colors, and for instance, we recently identified a gene that when removed, induces widespread ultraviolet-iridescence in butterflies normally devoid of this color. These experiments illustrate how evo-devo can delve into the genome-to-phenome relationship, and probe how evolution has been tinkering with a genetic toolkit of developmental genes involved in pattern and cell specification.

Biography: Dr. Arnaud Martin is an assistant professor at the George Washington University DC. He earned a Master in Cell and Developmental Biology at the Ecole Normale Superieure de Lyon, and then worked for the past 15 years on the genetic basis of color pattern formation for 15 years, between a PhD at UC Irvine with Bob Reed, a split post-doc with Bob Reed (Cornell U) and Tom Schilling (UC Irvine), and a post-doc with Nipam Patel (UC Berkeley). His research focuses on deciphering the developmental mechanisms that make butterfly wings a crucible of morphological diversity, and he is also sponsored by the NSF to establish the pantry mealmoth as a laboratory system for studying lepidopteran insects. He has 9 years of experience applying CRISPR techniques to non-model organisms, interrogating the gene-phenotype relationship with DNA editing experiments that tweak body region identity (Hox genes), morphogenetic signaling and pattern formation (Wnt pathway), or the identity of iridescent ultraviolet colors. He also developed a laboratory course where undergraduate students generate butterfly wing mutants in the classroom, from experimental design to embryo microinjection of CRISPR reagents.

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