title: The tomato I gene for Fusarium wilt resistance encodes an atypical leucine-rich repeat receptor-like protein whose function is nevertheless dependent on SOBIR1 and SERK3/BAK1.
abstract: We have identified the tomato I gene for resistance to the Fusarium wilt fungus Fusarium oxysporum f. sp. lycopersici (Fol) and show that it encodes a membrane-anchored leucine-rich repeat receptor-like protein (LRR-RLP). Unlike most other LRR-RLP genes involved in plant defence, the I gene is not a member of a gene cluster and contains introns in its coding sequence. The I gene encodes a loopout domain larger than those in most other LRR-RLPs, with a distinct composition rich in serine and threonine residues. The I protein also lacks a basic cytosolic domain. Instead, this domain is rich in aromatic residues that could form a second transmembrane domain. The I protein recognises the Fol Avr1 effector protein, but, unlike many other LRR-RLPs, recognition specificity is determined in the C-terminal half of the protein by polymorphic amino acid residues in the LRRs just preceding the loopout domain and in the loopout domain itself. Despite these differences, we show that I/Avr1-dependent necrosis in Nicotiana benthamiana depends on the LRR receptor-like kinases (RLKs) SERK3/BAK1 and SOBIR1. Sequence comparisons revealed that the I protein and other LRR-RLPs involved in plant defence all carry residues in their last LRR and C-terminal LRR capping domain that are conserved with SERK3/BAK1-interacting residues in the same relative positions in the LRR-RLKs BRI1 and PSKR1. Tyrosine mutations of two of these conserved residues, Q922 and T925, abolished I/Avr1-dependent necrosis in N. benthamiana, consistent with similar mutations in BRI1 and PSKR1 preventing their interaction with SERK3/BAK1.
authors.affiliation: Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT, Australia.
authors.forename: Ann-Maree
authors.initials: AM
authors.lastname: Catanzariti
authors.affiliation: Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT, Australia.
authors.forename: Huong T T
authors.initials: HT
authors.lastname: Do
authors.affiliation: Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT, Australia.
authors.forename: Pierrick
authors.initials: P
authors.lastname: Bru
authors.affiliation: Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Mara
authors.initials: M
authors.lastname: de Sain
authors.affiliation: CSIRO Agriculture and Food, Centre for Environment and Life Sciences, Wembley, WA, Australia.
authors.forename: Louise F
authors.initials: LF
authors.lastname: Thatcher
authors.affiliation: Swammerdam Institute for Life Sciences, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: Martijn
authors.initials: M
authors.lastname: Rep
authors.affiliation: Division of Plant Sciences, Research School of Biology, The Australian National University, Acton, ACT, Australia.
authors.forename: David A
authors.identifier: http://orcid.org/0000-0001-8809-5822
authors.initials: DA
authors.lastname: Jones
mesh_terms: D005670:Fusarium / Q000472:pathogenicity*; D000090263:Leucine-Rich Repeat Proteins; D018551:Solanum lycopersicum / Q000235:genetics / Q000378:metabolism* / Q000382:microbiology*; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000090263:Leucine-Rich Repeat Proteins; D010940:Plant Proteins; D011506:Proteins; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases
keywords: 
  Solanum lycopersicum
  ; 
  Solanum pimpinellifolium
  ; Fusarium oxysporum f. sp. lycopersici; Fusarium wilt; leucine-rich repeat; plant disease resistance gene; receptor-like protein; tomato