Plant Growth-Promoting Fungus, Trichoderma koningi Suppresses Isoflavonoid Phytoalexin Vestitol Production for Colonization on/in the Roots of Lotus japonicus

Abstract

The relationship between the colonization of Lotus japonicus by plant growth-promoting fungi (PGPF) and biosynthesis of the isoflavonoid phytoalexin vestitol, a major defensive response of leguminous plants, was analyzed. When PGPF including Trichoderma koningi, Fusarium equiseti, and Penicillium simplicissimum were inoculated onto L. japonicus roots, only T. koningi colonized the roots long-term and increased plant dry weight (126%). Microscopic observations of transverse sections of roots colonized by T. koningi demonstrated intercellular hyphal growth and the formation of yeast-like cells. The induction of plant defenses by fungal infections was examined by Northern analysis of genes involved in vestitol biosynthesis and HPLC of vestitol production in L. japonicus. Inoculation with symbiotic Mesorhizobium loti did not induce any accumulation of the transcripts. T. koningi immediately suppressed transcript levels to those induced by M. loti. The vestitol transuded from roots by T. koningi was detected at a level equivalent to that transuded by M. loti. Other PGPF and Calonectoria ilicola pathogenic to soybean but not to L. japonicus, stimulated continuous expression of genes and exudation of vestitol. These PGPF resembled mycorrhizal fungi in the establishment of symbiotic associations rather than fungal parasites.

Discriminative Phytoalexin Accumulation inLotus japonicusagainst Symbiotic and Non-Symbiotic Microorganisms and Related Chemical Signals

“…These results complement and extend the finding 10) that a plant growth-promoting fungus, Trichoderma koningi, suppresses vestitol production (28% of GSH treatment) and that M. loti causes only a low level of vestitol, while other fungi (Penicillium, Fusarium, and Calonectoria) induce phytoalexin to a level similar to GSH treatment. One of possible mechanisms of the suppression of defense responses by plant growthpromoting microbes and rhizobia is interference with the production of the defense hormone ethylene in host cells through, for example, the action of 1-aminocyclopropane-1-carboxylic acid deaminase.…”

Plant-beneficial effects of Trichoderma and of its genes

“…The ability to colonize plant roots depends strongly on the capacity of each strain to tolerate them. In Trichoderma, this resistance has been associated with the presence of ABC transport systems, which are key factors in the multiple interactions established by Trichoderma biocontrol strains with other microbes in a potentially toxic or antagonistic environment (Ruocco et al, 2009), with rapid degradation of the phenolic compounds exuded from plants (Chen et al, 2011), and with the suppression of phytoalexin production, as detected in Lotus japonicus during colonization with Trichoderma koningii (Masunaka et al, 2011). In a proteome analysis, a small secreted cysteine-rich protein (SSCP) was identified in T. harzianum and T. atroviride, proving to be a homologue of the avirulence protein Avr4 from Cladosporium fulvum .…”

Effect of Trichoderma Viride as Biofertilizer on Growth and Yield of Wheat

“…Other researchers reported that elicitors released by Trichoderma are involved in triggering expressions of defense protein within the plant to induce plant immunity against pathogens and, in turn, improve plant growth [22]. Trichoderma koningi that colonized the roots of Lotus japonicas was found to produce is flavonoid and phytoalexinvesitol and increase plant dry weight [23]. Since a few works is done to understand the impact of Trichoderma and wheat, this study on the wheat plant is done to understand itsrole as fungicides and/or growth promoters.…”