Fusarium oxysporum and its bacterial consortium promote lettuce growth and expansin A5 gene expression through microbial volatile organic compound (MVOC) emission.
Fusarium oxysporum MSA 35 [wild-type (WT) strain] is a nonpathogenic Fusarium strain, which exhibits antagonistic activity to plant pathogenic F. oxysporum isolates. The fungus lives in association with a consortium of ectosymbiotic bacteria. The WT strain, when cured of the bacterial symbionts [the cured (CU) form], is pathogenic, causing wilt symptoms similar to those of pathogenic F. oxysporum f. sp. lactucae. Both WT and CU MSA 35 strains produce microbial volatile organic compounds (MVOCs), but with a different spectrum. In vitro dual culture assays were used to assess the effects of the MVOCs produced by WT and CU strains of F. oxysporum MSA 35 on the growth and expansin gene expression of lettuce seedlings. An increase in the root length (95.6%), shoot length (75.0%) and fresh weight (85.8%) was observed only after WT strain MVOCs exposure. Leaf chlorophyll content was significantly enhanced (68%) in WT strain MVOC-treated seedlings as compared with CU strain volatiles and nontreated controls. β-Caryophyllene was found to be one of the volatiles released by WT MSA 35 responsible for the plant growth promotion effect. Semi-quantitative and quantitative reverse transcription-PCR assays indicated a significant difference in the expansin gene expression level between leaf (6.7-fold) and roots (4.4-fold) exposed to WT strain volatiles when compared with the CU strain volatiles and those that were nonexposed.
Centre of Competence for the Innovation in the Agro-Environmental field, Agroinnova, University of Torino, Grugliasco, Italy. daniela.minerdi@unito.it
Daniela
D
Minerdi
Simone
S
Bossi
Massimo E
ME
Maffei
Maria Lodovica
ML
Gullino
Angelo
A
Garibaldi
D001419:Bacteria / Q000254:growth & development* / Q000378:metabolism; D002473:Cell Wall / Q000378:metabolism; D018744:DNA, Plant / Q000235:genetics; D005670:Fusarium / Q000254:growth & development* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D018545:Lactuca / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000382:microbiology; D018515:Plant Leaves / Q000378:metabolism / Q000382:microbiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000378:metabolism / Q000382:microbiology; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes / Q000032:analysis / Q000378:metabolism / Q000494:pharmacology; D013559:Symbiosis; D055549:Volatile Organic Compounds / Q000032:analysis* / Q000378:metabolism / Q000494:pharmacology
D018744:DNA, Plant; D010940:Plant Proteins; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes; D055549:Volatile Organic Compounds; C095825:expansin protein, plant; C024714:caryophyllene