The Barley HvSTP13GR mutant triggers resistance against biotrophic fungi

High-yielding and stress resistant crops are essential to ensure future food supply. Barley is an important crop to feed livestock and to produce malt, but the annual yield is threatened by pathogen infections. Pathogens can trigger an altered sugar partitioning in the host plant, that possibly leads to an advantage for the pathogen. Hampering these processes represents a promising strategy to potentially increase resistance. We analyzed the response of the barley monosaccharide transporter HvSTP13 towards biotic stress and its potential use for plant protection. The expression of HvSTP13 increased upon bacterial and fungal PAMP application, suggesting a PAMP-triggered signaling that converged on the transcriptional induction of the gene. Promoter studies indicate a region that is likely targeted by transcription factors downstream of PAMP-triggered immunity pathways. We confirmed that the non-functional HvSTP13GR variant confers resistance against an economically relevant biotrophic rust fungus, in barley. In addition, we established targeted CRISPR/Cas9 cytosine base editing in barley protoplasts to generate alternative HvSTP13 mutants and characterized the sugar transport activity and subcellular localization of the proteins. These mutants represent promising variants for future resistance analysis. Our experimental setup provides basal prerequisites to further decode the role of HvSTP13 in response to biological stress. Moreover, in line with other studies, our experiments indicate that the alteration of sugar partitioning pathways, in a host pathogen interaction, is a promising approach to achieve broad and durable resistance in plants.