Genetic Code Expansion and Synthetic Genetic Circuits That Can Count for Precision Control of Plant and Microbial Gene Expression

Precision engineering of plants and their microbiomes requires genetic tools that control gene expression with high spatial, temporal, and molecular specificity. This talk presents two synthetic biology platforms addressing this challenge. First, we use genetic code expansion to build a chemical communication channel between plants and soil bacteria, using the non-canonical amino acid O-methyl-L-tyrosine (OMY) as a model signal. We engineer Bacillus subtilis to activate gene expression in an OMY-dependent manner, and engineer Arabidopsis, tomato, and poplar to biosynthesize OMY. Plant-derived OMY activates gene expression in both model and wild soil bacteria, and tissue-specific biosynthesis gives on-demand, spatially targeted control over microbial activity, establishing non-canonical amino acids as a tool for programming plant-microbe partnerships. Second, we develop a synthetic genetic circuit that can count and differentially respond to repeating signals to independently manipulate gene expression in plant roots that are molecularly identical but functionally distinct. Our synthetic genetic counter circuit tracks sequential branching events and drives distinct gene expression in each root branch order, letting us begin to probe how individual branches contribute to root system function. Together, these tools open new ways to control gene expression across kingdoms and developmental time.

Speaker: Jennifer Brophy, PhD, Stanford University