title: Reduced susceptibility of tomato stem to the necrotrophic fungus Botrytis cinerea is associated with a specific adjustment of fructose content in the host sugar pool.
abstract: Plant soluble sugars, as main components of primary metabolism, are thought to be implicated in defence against pathogenic fungi. However, the function of sucrose and hexoses remains unclear. This study aimed to identify robust patterns in the dynamics of soluble sugars in sink tissues of tomato plants during the course of infection by the necrotrophic fungus Botrytis cinerea . Distinct roles for glucose and fructose in defence against B. cinerea were hypothesized.
  
  
  
  We examined sugar contents and defence hormonal markers in tomato stem tissues before and after infection by B. cinerea , in a range of abiotic environments created by various nitrogen and water supplies.
  
  
  
  Limited nitrogen or water supplies increased tomato stem susceptibility to B. cinerea . Glucose and fructose contents of tissues surrounding infection sites evolved differently after inoculation. The fructose content never decreased after inoculation with B. cinerea , while that of glucose showed either positive or negative variation, depending on the abiotic environment. An increase in the relative fructose content (defined as the proportion of fructose in the soluble sugar pool) was observed in the absence of glucose accumulation and was associated with lower susceptibility. A lower expression of the salicylic acid marker PR1a , and a lower repression of a jasmonate marker COI1 were associated with reduced susceptibility. Accordingly, COI1 expression was positively correlated with the relative fructose contents 7 d after infection.
  
  
  
  Small variations of fructose content among the sugar pool are unlikely to affect intrinsic pathogen growth. Our results highlight distinct use of host glucose and fructose after infection by B. cinerea and suggest strongly that adjustment of the relative fructose content is required for enhanced plant defence.
authors.affiliation: PSH unit, INRA, F-84914 Avignon, France.
authors.forename: François
authors.initials: F
authors.lastname: Lecompte
authors.affiliation: Plant pathology unit, INRA, F-84140 Montfavet, France.
authors.forename: Philippe C
authors.initials: PC
authors.lastname: Nicot
authors.affiliation: PSH unit, INRA, F-84914 Avignon, France.
authors.forename: Julie
authors.initials: J
authors.lastname: Ripoll
authors.affiliation: Plant pathology unit, INRA, F-84140 Montfavet, France.
authors.forename: Manzoor A
authors.initials: MA
authors.lastname: Abro
authors.affiliation: UMR Qualisud, Université d'Avignon et des Pays du Vaucluse, F-84916 Avignon, France.
authors.forename: Astrid K
authors.initials: AK
authors.lastname: Raimbault
authors.affiliation: UMR Qualisud, Université d'Avignon et des Pays du Vaucluse, F-84916 Avignon, France.
authors.forename: Félicie
authors.initials: F
authors.lastname: Lopez-Lauri
authors.affiliation: PSH unit, INRA, F-84914 Avignon, France.
authors.forename: Nadia
authors.initials: N
authors.lastname: Bertin
mesh_terms: D020171:Botrytis / Q000502:physiology*; D005632:Fructose / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D018551:Solanum lycopersicum / Q000378:metabolism* / Q000382:microbiology*; D010935:Plant Diseases / Q000382:microbiology*; D010937:Plant Growth Regulators / Q000378:metabolism; D018547:Plant Stems / Q000378:metabolism / Q000382:microbiology
chemical_list: D010937:Plant Growth Regulators; D005632:Fructose; D005947:Glucose
keywords: Botrytis cinerea; Tomato (Solanum lycopersicum); fructose; glucose; hormones; necrotrophic fungi; plant defence; soluble sugars