What is it about?

Susceptibility (S) genes are plant genes that facilitate pathogen infection. Inactivation of S genes has been considered a promis- ing strategy to obtain broad-spectrum and durable resistance in crops. We characterized two orthologs of the Arabidopsis S gene DMR6 in tomato: SlDMR6-1 and SlDMR6-2. We show that SlDMR6-1, but not SlDMR6-2, is associated with plant immunity. Remarkably, Sldmr6-1 mutants display enhanced resistance to bacterial, oomycete, and fungal pathogens. This phenotype correlates with increased levels of the defense hormone salicylic acid (SA) and enhanced transcriptional activation of plant immune responses. We also demonstrate that SlDMR6-1 and SlDMR6-2 convert SA into its inactive form, 2,5-DHBA, indicating that they play a role in SA homeostasis.

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Why is it important?

Despite all the advances in the study of the plant immune system and the understanding of SA metabolism, it is still challenging to convert this accumulated knowledge from model plants into suitable applications for crop improvement. In this work, we present a model-to-crop translational work, in which we identify two DMR6 orthologs in tomato and show a comprehensive characterization of the effects of their CRISPR inactivation under laboratory and field conditions. Based on biochemical assays, we show that both tomato DMR6 proteins are SA-5 hydroxylases (S5H) that catalyze the formation of 2,5-DHBA, demonstrating that these proteins are indeed important players in the SA catabolic pathway. These results not only contribute to the understanding of SA homeostasis in plant– pathogen interactions, but also constitute a promising strategy for engineering broad-spectrum and long-lasting disease resistance in crops.


The use of genetically modified/CRISPR-edited crops in agriculture can be a sustainable approach to ensure food security for present and future generations. Climate changes and the increasing human population definitely require the use of more efficient and sustainable practices in agriculture. Our work fits in this context, as it greatly contributes to the understanding of a promising strategy for engineering broad-spectrum and durable disease resistance in crops. I hope you find our article interesting and enjoy reading it!

Daniela de Toledo Thomazella
University of California at Berkeley

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This page is a summary of: Loss of function of a DMR6 ortholog in tomato confers broad-spectrum disease resistance, Proceedings of the National Academy of Sciences, July 2021, Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.2026152118.
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