title: Salicylic acid prevents Trichoderma harzianum from entering the vascular system of roots.
abstract: Trichoderma is a soil-borne fungal genus that includes species with a significant impact on agriculture and industrial processes. Some Trichoderma strains exert beneficial effects in plants through root colonization, although little is known about how this interaction takes place. To better understand this process, the root colonization of wild-type Arabidopsis and the salicylic acid (SA)-impaired mutant sid2 by a green fluorescent protein (GFP)-marked Trichoderma harzianum strain was followed under confocal microscopy. Trichoderma harzianum GFP22 was able to penetrate the vascular tissue of the sid2 mutant because of the absence of callose deposition in the cell wall of root cells. In addition, a higher colonization of sid2 roots by GFP22 compared with that in Arabidopsis wild-type roots was detected by real-time polymerase chain reaction. These results, together with differences in the expression levels of plant defence genes in the roots of both interactions, support a key role for SA in Trichoderma early root colonization stages. We observed that, without the support of SA, plants were unable to prevent the arrival of the fungus in the vascular system and its spread into aerial parts, leading to later collapse.
authors.affiliation: Departamento de Fisiología Vegetal, Centro Hispano-Luso de Investigaciones Agrarias (CIALE), Facultad de Biología, Universidad de Salamanca, C/Río Duero 12, Campus de Villamayor, 37185, Salamanca, Spain.
authors.forename: Ana
authors.initials: A
authors.lastname: Alonso-Ramírez
authors.forename: Jorge
authors.initials: J
authors.lastname: Poveda
authors.forename: Ignacio
authors.initials: I
authors.lastname: Martín
authors.forename: Rosa
authors.initials: R
authors.lastname: Hermosa
authors.forename: Enrique
authors.initials: E
authors.lastname: Monte
authors.forename: Carlos
authors.initials: C
authors.lastname: Nicolás
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000382:microbiology*; D015169:Colony Count, Microbial; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D005936:Glucans / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000378:metabolism; D063245:Plant Development / Q000187:drug effects; D018517:Plant Roots / Q000382:microbiology*; D058526:Plant Vascular Bundle / Q000187:drug effects / Q000382:microbiology*; D060888:Real-Time Polymerase Chain Reaction; D020156:Salicylic Acid / Q000494:pharmacology*; D014242:Trichoderma / Q000187:drug effects / Q000502:physiology*
chemical_list: D005936:Glucans; D049452:Green Fluorescent Proteins; C048306:callose; D020156:Salicylic Acid
keywords: Arabidopsis thaliana; Trichoderma; callose deposition; plant defence; root colonization; salicylic acid