Targeted Amino Acid Substitutions in a Trichoderma Peptaibol Confer Activity against Fungal Plant Pathogens and Protect Host Tissues from Botrytis cinerea Infection

Abstract

Fungal species belonging to the Trichoderma genus are commonly used as biocontrol agents against several crop pathogens. Among their secondary metabolites, peptaibols are helical, antimicrobial peptides, which are structurally stable even under extreme pH and temperature conditions. The promise of peptaibols as agrochemicals is, however, hampered by poor water solubility, which inhibits efficient delivery for practical use in crop protection. Using a versatile synthetic strategy, based on green chemistry procedures, we produced water-soluble analogs of the short-length peptaibol trichogin. Although natural trichogin was inactive against the tested fungal plant pathogens (Botrytis cinerea, Bipolaris sorokiniana, Fusarium graminearum, and Penicillium expansum), three analogs completely inhibited fungal growth at low micromolar concentrations. The most effective peptides significantly reduced disease symptoms by B. cinerea on common bean and grapevine leaves and ripe grape berries without visible phytotoxic effects. An in-depth conformational analysis featuring a 3D-structure–activity relationship study indicated that the relative spatial position of cationic residues is crucial for increasing peptide fungicidal activity.

The Emericellipsins A–E from an Alkalophilic Fungus Emericellopsis alkalina Show Potent Activity against Multidrug-Resistant Pathogenic Fungi

“…were designed and synthesized to increase the water solubility and antifungal activity against an economically important fungal plant pathogen, Botrytis cinerea . These molecules have single amino acid substitutions, predominantly Gly/Lys located inside a helical structure [ 55 ]. It was shown that this modification increased peptide amphiphilicity and did not lead to critical changes of 3D orientation.…”

“…The results revealed resistance to fluconazole and intraconazole and low susceptibility to caspofungin. Among the clinically approved antifungal drugs, only amphotericin B displays a comparable activity profile towards the drug-resistant C. neoformans and C. laurentii isolates obtained from HIV-positive patients with cryptococcal meningitis [ 28 , 31 , 55 , 56 ].…”

Transcriptomic and Ultrastructural Analyses of Pyricularia Oryzae Treated With Fungicidal Peptaibol Analogs of Trichoderma Trichogin

“…Therefore, the present study has been designed to test the possible use of small antimicrobial peptides (AMPs), called “peptaibols,” as biopesticides to control rice blast disease caused by P. oryzae . Recently, water-soluble analogs of the T. longibrachiatum short-length peptaibol trichogin GA IV ( Szekeres et al, 2005 ) have been synthesized using a versatile synthetic strategy designed to reduce the impact on the environment ( De Zotti et al, 2020 ). Three of these analogs completely inhibited the growth of Botrytis cinerea in vitro at low micromolar concentrations, and the most effective peptides significantly reduced gray mold symptoms on common bean, grapevine leaves and ripe grape berries ( De Zotti et al, 2020 ).…”

Analogs of a Natural Peptaibol Exert Anticancer Activity in Both Cisplatin- and Doxorubicin-Resistant Cells and in Multicellular Tumor Spheroids

“…We recently found that water-soluble peptaibol analogs, featuring Gly-to-Lys substitutions, possess anticancer activity [6]. Besides, through the application of a biorational approach, we recently designed water-soluble peptaibol analogs with improved bioactivity against fungal plant pathogens [9].…”

“…The synthesis of peptaibols is not trivial, as the steric hindrance of Aib makes it poorly reactive. Nonetheless, we have recently proposed an effective, ecofriendly strategy [9] that we are also applying here. Such a procedure for the synthesis of peptaibols is also less expensive than the standard protocol, and represents a step forward towards the translation of peptaibols to the market; however, it did not solve the main problem connected with the production of peptaibols: the presence of a C-terminal aminoalcohol (featured in the natural sequences), that forces the use of costly, preloaded resins for their production by solid-phase peptide synthesis [10].…”