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.

Tomato progeny inherit resistance to the nematode Meloidogyne javanica linked to plant growth induced by the biocontrol fungus Trichoderma atroviride

“…This last gene is involved in the formation and deposition of lignin in the tomato cell wall33, and its repression has been described in tomato-RKN compatible interactions7. The PR1 and TPX1 downregulation observed at 24 h in w/Ta and Ta/Mj tomato roots agrees with the transient repression in Arabidopsis of SA-dependent immune responses to allow Trichoderma early root colonization34, although a subsequent SA-mediated reactivation of defenses is necessary to avoid root invasion by Trichoderma 35. Interestingly, the similar PR1 time course expression profile observed in w/Ta and Ta/Mj treatments (Fig.…”

Effects of Trichothecene Production on the Plant Defense Response and Fungal Physiology: Overexpression of the Trichoderma arundinaceum tri4 Gene in T. harzianum

“…The production of specific phytotoxic compounds and direct attack by a pathogen are signals which plants detect and respond to, resulting in the upregulation of expression of defense-related genes, particularly SA-related genes. SA is involved in the induction of callose deposition in plant cell walls, resulting in resistance to fungal colonization (40). In this way, production of trichodermol might allow the plant to identify a particular producer fungus as a potential pathogen-like organism.…”

Interactions between Trichoderma harzianum and defoliating Verticillium dahliae in resistant and susceptible wild olive clones

“…Endophytic infections by T. asperellum strains Bt3 and T25 have also been reported in Picual olive plants (Carrero‐Carrón et al ., ). Previous CLSM studies have demonstrated that T. harzianum GFP22 is efficient in rhizosphere colonization of Arabidopsis thaliana and cucumber plants (Samolski et al ., ; Alonso‐Ramírez et al ., ). Similarly, Ruano‐Rosa et al .…”

“…Previous studies have demonstrated the value of CLSM for monitoring infection and colonization of herbaceous and woody hosts by V. dahliae (Prieto et al ., ; Zhang et al ., ), as well as for simultaneous visualization of this pathogen and the biocontrol strains P. fluorescens PICF7 and T. harzianum GFP22 (Prieto et al ., ; Ruano‐Rosa et al ., ). The use of the fluorescent transformant D V. dahliae V138I‐YFP, obtained in the present study, and of the commonly employed strain T. harzianum GFP22 (Chacón et al ., ; Samolski et al ., ; Alonso‐Ramírez et al ., ; Ruano‐Rosa et al ., ), allowed simultaneous examination of the growth of D V. dahliae and T. harzianum in olive and wild olive plants by means of CLSM. The newly developed V. dahliae YFP transformant proved suitable for the study because it did not show any difference compared with the wild type strain V. dahliae V‐138I regarding morphology and growth rate on different culture media.…”

“…Trichoderma harzianum GFP22, a GFP‐marked strain derived from the wildtype strain T. harzianum CECT 2413 (Spanish Type Culture Collection, Burjassot, Spain), kindly provided by Dr Ana Rincón (University of Seville, Spain), was used as the antagonistic fungus. Strains CECT 2413 (referred to as T34 strain) and GFP22 are commonly used in basic biocontrol (Lorito et al ., ) and CLSM (Samolski et al ., ; Alonso‐Ramírez et al ., ; Ruano‐Rosa et al ., ) studies, respectively. Monoconidial V. dahliae V‐138I isolate (Department of Crop Protection culture collection, Instituto de Agricultura Sostenible, CSIC, Córdoba, Spain; referred to as V‐138I strain), previously typed to lineage 1A, D pathotype and race 2 (Jiménez‐Díaz et al ., ), was used as a host in the transformation experiments to express yellow fluorescent protein (YFP) in V. dahliae .…”