Transcriptional Rewiring: Synthetic and Evolutionary Processes Governing Plant Environmental Stress Responses

Plant defence responses are modulated by substantial transcriptional reprogramming, up to 40% of the genome can be differentially expressed following pathogen challenge. High temporal resolution differential expression analysis and subsequent network inference has revealed a large transcriptional networks with a complex hierarchies. Overall this indicates that transcriptional factors play an important role in the defence response. The complexity, diversity and redundancy in these defence response networks further suggests interesting evolutionary principles may govern and give rise to these highly structured and plastic networks. Previously we have shown that a synthetic technique known as genetic rewiring, where the open reading frames of selected transcription factors are fused to different promoters altering the natural expression of the regulator, can be used to synthetically evolve novel phenotypic diversity. As a transcription factor can potentially regulate thousands of target genes, alteration of its natural expression has the potential to generate radically new phenotypes through cascading regulatory events. We have shown through this approach, in yeast, that heterologous protein expression can be significantly enhanced using this rewiring approach. Furthermore, network analysis reveals that rewired open reading frames and promoters possess characteristic topological network features that can serve as predictive measures for future rewiring endeavours. As such in conjunction with a presentation of our work on rewiring the yeast transcriptome I will briefly discuss how we are using a combined systems and synthetic biology approach to first construct large scale transcriptional networks responding to pathogen challenge in plants. Secondly, I will show how through a process of topological network analysis how we are now selecting promoters and open reading frames which we will use to rewire the plant defence transcriptome. This novel transciptome diversity will be used to help reveal key regulatory points and potential weaknesses in these networks as well as highlighting potential solutions to help improve tolerance to plant pathogens.