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Abstract:
Horizontal gene transfer (HGT) is the exchange of genetic material between non-related species and it has been shown to contribute to the evolution of nematodes, specifically for plant-parasitism. Pristionchus are microbial-feeding nematodes and have horizontally acquired cellulase genes from eukaryotic origin. We recently demonstrated that these cellulases are likely produced in the gland cells and are secreted to digest the resilient structure of bacterial biofilms increasing the fitness of the nematodes [1]. However, how these horizontally acquired genes are regulated by the recipient is still unclear. We found that the expression levels and patterns of cellulase genes are affected by environmental cues, such as starvation and bacterial foods. Moreover, as P. pacificus represents an example of developmental plasticity which results in two distinct life styles, a predator and a straight microbial-feeder, we have found higher cellulase expression levels associated with the microbial- feeders. Thus, cellulase genes have integrated into the complex gene regulatory networks of P. pacificus. Here, we are investigating the upstream regulators of the main cellulase gene (cel-2) in P. pacificus. We are conducting an EMS-induced mutagenesis screen on a fluorescent reporter line driven by the promotor of cel-2 (cel-2p::RFP) to identify mutants with abnormal cel-2 expression. Subsequently, we will ascertain the causative genes with genetic mapping and CRISPR genome-editing. With further characterization of these genes and illustration of the biological pathways involved, we will be able to demonstrate the integration of horizontally acquired genes in P. pacificus and provide new insights into the molecular mechanism of HGT in animal evolution.
