Abstract
Evolution of metabolic herbicide resistance is a major issue for weed management. Few genes and regulatory mechanisms have been identified, particularly in dicotyledonous weed species. We identified putative causal genes and regulatory mechanism for tembotrione resistance in Palmer amaranth (Amaranthus palmeri). Cytochrome P450 candidate genes were identified through RNA-seq analysis. We validated their functions using heterologous expression in Saccharomyces cerevisae. Promoters of the candidate P450 genes were analysed. We performed QTL mapping to identify genomic regions associated with resistance. CYP72A1182 metabolized tembotrione in a heterologous system. The CYP72A1182 gene had increased expression in other A. palmeri populations resistant to multiple herbicides, including tembotrione. Resistant plants exhibited polymorphisms in the promoter of CYP72A1182. We identified quantitative trait loci linked to herbicide resistance, including one on chromosome 4 approximately 3 Mb away from CYP72A1182. CYP72A1182 is likely involved in tembotrione resistance in A. palmeri. Increased expression of this gene could be due to cis-regulation in the promoter, as well as trans-regulation from transcription factors, and further studies are in progress to test this hypothesis. The elucidation of regulatory genes is crucial for developing innovative weed management approaches and target-based novel herbicide molecules.