Mayfield Lab

Front Row: William Ansari, Elizabeth Specht, Steven Mayfield, Miller Tran, Daniel Barrera, Ryan Georgianna, Wendy Stegman, Jennifer Griffin.  Top Row: Travis Muff, Javier Gimple, James Hyun, Joseph Ostrand, Jamie Gregory, Amy Hoang, David Doerner, Brian Pierini.

smayfield@ucsd.edu

Stephen Mayfield, Principal Investigator

wansari@ucsd.edu

William Ansari , Graduate Student

William Ansari is a graduate student at UCSD.  His research is centered around the identification of suitable production strains and development of genetic engineering approaches to create ideal strains for production in both enclosed and outdoor settings.  Some of the trait modifications that he is pursuing include: total lipid content, lipid profile alteration, growth rate, salt tolerance, and overall biomass production.

danieljbarrera@gmail.com

Daniel Barrera, Graduate Student

Dan is an algal geneticist concentrating on the regulation of chloroplast genes by the nucleus.  Proteins synthesized in the nucleus are directed to the chloroplast to govern the many genes involved in producing the photosynthetic apparatus. Several of these genes contain robust regulatory elements that can be used to express transgenes encoding valuable recombinant proteins.  Our lab has demonstrated this by producing malarial antigens (vaccines) and anti-cancer antibody-toxin fusion molecules (immunotoxins) in algae chloroplasts.  By understanding how nuclear gene products interact with regulatory sequence elements of chloroplast genes, we can improve algae as an agricultural biotechnology platform.  Specifically, Dan is collecting data by utilizing high-throughput screening techniques involving insertional mutagenesis, fluorescence activated cell sorting, and competitive growth assays to select algae with enhanced agricultural traits of interest.  By combining high-throughput screens with next-generation sequencing technology and bioinformatics, Dan hopes to unveil and characterize genes of agricultural relevance in an emerging biotechnological platform.

jagimpel@ucsd.edu

Javier Gimpel , Graduate Student

Chloroplast promoters and UTRs have been thought to be specie-specific. We are testing whether regulatory regions from highly expressed chloroplast genes can be functional if used in heterologous organisms. We are transforming sequences from a wide range of photosynthetic organisms in our model algae C. reinhardtii. We are mainly interested in the psbA regulatory regions, but we are also extending to other genes such as tufA, atpA and psbD.

Membrane proteins are of great importance due to their potential as drug targets. However, they are difficult to express in a functional form in current non-mammalian expression systems. We are trying to express relevant membrane proteins such as GPCRs in Chlamydomonas chloroplast. Chloroplast have the advantage of high expression, proper folding machinery and the presence of extensive membranous systems such as the inner envelope and the thylakoids.

especht@ucsd.edu

Liz Specht, Graduate Student

It is known that much of the regulation of protein production in C. reinhardtii is controlled at the post-transcriptional level, but the mRNA elements responsible for this positive and negative regulation have only been identified in a limited number of genes. Liz is working to identify these elements in several highly expressed plastid genes in the hopes of constructing a synthetic UTR (untranslated region) for optimal transgene expression for high-value protein production.

Liz is also working on introducing a nuclear-localized version of RecA, the recombinase which C. reinhardtii produces naturally but which is normally targeted to the chloroplast. There is very little homologous recombination in the nuclear genome, so transgenes insert randomly, causing deleterious positional effects. If the native RecA can be retained within the nucleus, it may be possible to generate a high frequency of targeted insertions in the nuclear genome simply by adding homology to the transgene construct to direct its insertion.

dgeorgianna@ucsd.edu

Ryan Georgianna, Postdoctoral Fellow

Natural isolates of algae have evolved over millions of years to survive in diverse and often harsh environments. While the phenotypic plasticity of algae has served well for their continued persistence it is not necessary and potentially detrimental towards the development of elite algal production strains. Ryan's current work is focused on developing techniques for the genetic modification of non-model algal species, including biofuel candidate strains and marine algae. Additionally, he is working to further understand the genetic content of algae with regards to what makes a better production strain with a long term goal towards development of elite domesticated lines of algae. 

j1gregor@ucsd.edu

James Gregory, Postdoctoral Fellow

James Gregory's research focuses on further advancing Chlamydomonas reinhardtii as a heterologous expression system by developing the genetic tools, in conjunction with applying more high throughput screening methods, that will facilitate more rapid strain construction. He is applying these methods to construct a C. reinhardtii strain that produces specific malarial proteins that could serve as a potential 'green' vaccine for malaria that is economically viable. This work is currently being funded by the San Diego Foundation and SD-CAB.

tmuff@ucsd.edu

Travis Muff, Postdoctoral Fellow

brasala@ucsd.edu

Beth A. Rasala, Postdoctoral Fellow

Beth is investigating the regulation of protein translation in the chloroplast, including deciphering the role of key sequence elements within endogenous 5' untranslated regions in translation initiation.  She is also interested in improving heterologous protein accumulation yields in the algal chloroplast.  To address this question, she is conducting high-throughput screens for increased reporter gene expression.  Lastly, Beth has metabolically engineered C. reinhardtii for the accumulation of novel and commercially valuable products, including protein therapeutics.

mit005@ucsd.edu

Miller Tran, Postdoctoral Fellow

Miller Tran recently completed his PhD at the University of California San Diego, and is currently a postdoctoral fellow. His research focuses on developing algal chloroplasts as a "Next generation" expression platform for the production of valuable protein therapeutics. While the algal expression platform is still in its infantcy, Miller hopes to be a leader in this emerging field.

Philip Lee, Post-Doctoral Fellow, Ph.D. Molecular Microbiology, John Innes Centre, Norwich, UK 2004