title: A knowledge-based molecular screen uncovers a broad-spectrum OsSWEET14 resistance allele to bacterial blight from wild rice.
abstract: Transcription activator-like (TAL) effectors are type III-delivered transcription factors that enhance the virulence of plant pathogenic Xanthomonas species through the activation of host susceptibility (S) genes. TAL effectors recognize their DNA target(s) via a partially degenerate code, whereby modular repeats in the TAL effector bind to nucleotide sequences in the host promoter. Although this knowledge has greatly facilitated our power to identify new S genes, it can also be easily used to screen plant genomes for variations in TAL effector target sequences and to predict for loss-of-function gene candidates in silico. In a proof-of-principle experiment, we screened a germplasm of 169 rice accessions for polymorphism in the promoter of the major bacterial blight susceptibility S gene OsSWEET14, which encodes a sugar transporter targeted by numerous strains of Xanthomonas oryzae pv. oryzae. We identified a single allele with a deletion of 18 bp overlapping with the binding sites targeted by several TAL effectors known to activate the gene. We show that this allele, which we call xa41(t), confers resistance against half of the tested Xoo strains, representative of various geographic origins and genetic lineages, highlighting the selective pressure on the pathogen to accommodate OsSWEET14 polymorphism, and reciprocally the apparent limited possibilities for the host to create variability at this particular S gene. Analysis of xa41(t) conservation across the Oryza genus enabled us to hypothesize scenarios as to its evolutionary history, prior to and during domestication. Our findings demonstrate that resistance through TAL effector-dependent loss of S-gene expression can be greatly fostered upon knowledge-based molecular screening of a large collection of host plants.
authors.affiliation: UMR IPME, IRD-CIRAD-Université Montpellier 2, Montpellier, France.
authors.forename: Mathilde
authors.initials: M
authors.lastname: Hutin
authors.affiliation: UMR DIADE IRD/UM2, BP 64501, 34394, Montpellier Cedex 5, France.
authors.forename: François
authors.initials: F
authors.lastname: Sabot
authors.affiliation: UMR DIADE IRD/UM2, BP 64501, 34394, Montpellier Cedex 5, France.
authors.forename: Alain
authors.initials: A
authors.lastname: Ghesquière
authors.affiliation: UMR IPME, IRD-CIRAD-Université Montpellier 2, Montpellier, France.
authors.forename: Ralf
authors.initials: R
authors.lastname: Koebnik
authors.affiliation: UMR IPME, IRD-CIRAD-Université Montpellier 2, Montpellier, France.
authors.forename: Boris
authors.initials: B
authors.lastname: Szurek
mesh_terms: D000483:Alleles; D001426:Bacterial Proteins / Q000378:metabolism; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D060467:Disease Resistance / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D054884:Host-Pathogen Interactions; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D012275:Oryza / Q000235:genetics* / Q000378:metabolism / Q000382:microbiology; D010802:Phylogeny; D010935:Plant Diseases / Q000235:genetics* / Q000382:microbiology; D018515:Plant Leaves / Q000235:genetics / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins / Q000145:classification / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017384:Sequence Deletion; D013045:Species Specificity; D014774:Virulence; D014974:Xanthomonas / Q000145:classification / Q000472:pathogenicity
chemical_list: D001426:Bacterial Proteins; D009004:Monosaccharide Transport Proteins; D010940:Plant Proteins
keywords: Oryza barthii; SWEET; TAL effector; Xanthomonas oryzae; susceptibility (S) gene; xa41(t)