A Novel l-Amino Acid Oxidase from Trichoderma harzianum ETS 323 Associated with Antagonism of Rhizoctonia solani

Abstract

Trichoderma spp. are used as biocontrol agents against phytopathogens such as Rhizoctonia solani, but their biocontrol mechanisms are poorly understood. A novel L-amino oxidase (Th-LAAO) was identified from the extracellular proteins of Trichoderma harzianum ETS 323. Here, we show a FAD-binding glycoprotein with the best substrate specificity constant for L-phenylalanine. Although the amino acid sequence of Th-LAAO revealed limited homology (16-24%) to other LAAO members, a highly conserved FAD-binding motif was identified in the N-terminus. Th-LAAO was shown to be a homodimeric protein, but the monomeric form was predominant when grown in the presence of deactivated Rhizoctonia solani. Furthermore, in vitro assays demonstrated that Th-LAAO had an antagonistic effect against Rhizoctonia solani and a stimulatory one on hyphal density and sporulation in T. harzianum ETS 323. These findings further our understanding of T. harzianum as a biocontrol agent and provide insight into the biological function of l-amino acid oxidase.

Distribution in Different Organisms of Amino Acid Oxidases with FAD or a Quinone As Cofactor and Their Role as Antimicrobial Proteins in Marine Bacteria

“…For example, the generation of hydrogen peroxide has been described from a physiological point of view as involved in antimicrobial processes. Among these processes, bacterial biofilm development [ 13 ], microbial competition related to biocontrol processes in fungi [ 14 ], protection of fish skin bacterial infections [ 15 ] and participation in the human immune system [ 16 ] are included. AAOs are also of interest in relation to their biotechnological applications [ 4 , 17 ].…”

Recombinant expression of an l‐amino acid oxidase from the fungus Hebeloma cylindrosporum in Pichia pastoris including fermentation

“…pastoris . It is known that snake venom LAAOs and a secreted LAAO from the fungus Trichoderma harzianum are glycosylated (Pollegioni et al, 2013; Yang et al, 2011). The sequence of hc LAAO4 contains four putative N‐glycosylation sites predicted by the NetNGlyc program at amino acid residues N54, N164, N193, and N331 (Figure A1).…”

Activation of Recombinantly Expressed l-Amino Acid Oxidase from Rhizoctonia solani by Sodium Dodecyl Sulfate

“…Most l -amino acid oxidases are active only as homodimers [ 4 ]. However, an l -AAO from the fungus Trichoderma harzianum ETS323 is secreted as an active monomeric or dimeric form depending on cultivation conditions [ 5 ]. Therefore, we analyzed the dimerization state of recombinant purified 9His- rs LAAO1 by size-exclusion chromatography (SEC).…”

“…FAD is regenerated by oxygen under emergence of hydrogen peroxide in the oxidative half-reaction. Most l -AAOs form dimers, but active monomers and dimers have been described for the same l -AAO from the fungus Trichoderma harzianum ETS323, depending on growth conditions [ 4 , 5 ].…”