Daniela Paula de Toledo Thomazella, Ph.D.

Research

The Staskawicz lab is exploring innovative strategies to engineer durable disease resistance in crops by targeting plant susceptibility genes. One such gene, DMR6 (Downy Mildew Resistance 6), has been identified as a conserved negative regulator of plant immunity across multiple species. While traditional resistance breeding relies on dominant resistance genes that can be rapidly overcome by evolving pathogens, inactivation of susceptibility genes such as DMR6 represents a promising alternative for achieving broad-spectrum and long-lasting resistance. Using a combination of molecular biology, plant genetics, biochemistry, and computational approaches, my project focused on the functional characterization of DMR6 orthologs in tomato and their application for crop improvement. We identified two DMR6 homologs and demonstrated that one of them, SlDMR6-1, is specifically induced upon pathogen infection and acts as a key regulator of plant susceptibility. Using CRISPR/Cas9-mediated genome editing, we generated loss-of-function mutants in this gene and showed that these plants display enhanced resistance to multiple classes of pathogens, including bacteria, oomycetes, and fungi, without major penalties on growth under controlled conditions. Mechanistically, we demonstrated that DMR6 encodes a salicylic acid (SA) 5-hydroxylase that modulates SA homeostasis by converting active SA into an inactive form. Loss of DMR6 function leads to elevated SA levels and a stronger activation of plant immune responses, particularly upon pathogen challenge. This work not only confirms a key biochemical mechanism underlying susceptibility but also provides a clear translational framework for engineering broad-spectrum disease resistance in crops. By targeting conserved susceptibility genes such as DMR6, this strategy has the potential to be extended to a wide range of agriculturally important species.