Joshua Derrick

“Developing Methods for Manipulating Meiotic Recombination in Zea mays”

Project Summary:

Meiosis is a cell division process in which cells reduce their chromosome number by ½ (2n->n). During this process, double stranded breaks (DSB) in chromosomal DNA are produced and then repaired to form either a crossover (CO) or non-crossover (NCO) event, resulting in recombinant chromosomes. Increasing the rate of CO formation as well controlling the location of CO events will allow accelerated crop breeding. My project focused on developing tools to manipulate CO formation in Zea mays.

Previous research from the Pawlowski lab has shown that the hypomethylation mutant zmet2 shows an increased CO rate. My goal was to mimic this effect using chemical treatments on premeiotic maize tassels, using demethylases such as 5-azacytidine. However, before using these demethylating agents, I needed to test the optimal delivery method to tassels using 5-ethynyl-2’-deoxyuridine, a DNA substitute that fluoresces after treatment..

In addition, I developed a tool to help analyze the frequency of the CO events: a vector that will be transformed into maize containing a Green Fluorescent Protein (GFP- tagged maize meiotic protein HEI10.  HEI10 is highly conserved among species and is required for the formation of class I COs, which account for about 85% of all crossovers. Antibodies have already been developed to image Hei10, but a GFP-tagged line will allow live-imaging of the protein, which could reveal more information on how CO events are formed.

My Experience:

This summer, I experienced a mix of wet lab biology and bioinformatics. I learned how to design, express and purify recombinant proteins, improved my cloning by tackling a more difficult transformation, gained experience with a 3D deconvolution microscope and learned how to analyze phylogenetic data. I also appreciated the exposure to the large and diverse field of plant biology through weekly seminars, and interactions with other interns and within my own lab. In addition, I gained skills in planning and independently scheduling a research project on a tight time scale.