Synthetic Promoter Development for Drought Stress Response in Hybrid Poplar

Abiotic stress, such as that caused by drought, is problematic to crop production, especially those for which irrigation is not economically feasible. Bioenergy crops, such as hybrid poplar, must be endowed with robust coping mechanisms for stress. To that end, we are partnering with collaborators to develop stress-inducible synthetic promoters to drive stress-coping genes only when needed by hybrid poplar plants. Our strategy is to mine poplar –omics data for signature promoter motifs that are drought-responsive, then combine motifs in multimers upstream of the core cauliflower mosaic virus (CaMV) -46 35S promoter region. Herein we found 30 candidate DNA motifs using p-value threshold of 0.01 from promoters of drought-responsive co-expressed genes. These domains each were comprised of 3 to 9 conserved motifs that were detected among the 30 candidate regions of approximately 100 bases each. Our mined domains, which included part of the native promoters were fused to a green fluorescent protein gene and screened under proxy drought stress in poplar mesophyll protoplasts. The inducible motifs have been synthesized into a purely synthetic promoter architecture and will be screened in a robotic protoplast system to determine temporal and spatial inducibility of drought stress response in poplar.