Thaumatin-like proteins (TLPs), which are defined as pathogenesis-related protein family 5 (PR5) members, are common plant proteins involved in defense responses and confer antifungal activity against many plant pathogens. Our earlier studies have reported that the TaTLP1 gene was isolated from wheat and proved to be involved in wheat defense in response to leaf rust attack. The present study aims to identify the interacting proteins of TaTLP1 and characterize the role of the interaction between wheat and Puccinia triticina ( Pt ). Pull-down experiments designed to isolate the molecular target of TaTLP1 in tobacco resulted in the identification of TaPR1, a pathogenesis-related protein of family 1, and the interaction between TaTLP1 and TaPR1 was confirmed by yeast two-hybrid experiments (Y2H), bimolecular fluorescence complementation (BiFC), and co-immunoprecipitation (Co-IP). In vitro , TaTLP1 and TaPR1 together increased antifungal activity against Pt . In vivo , the disease resistance phenotype, histological observations of fungal growth and host responses, and accumulation of H 2 O 2 in TaTLP1-TaPR1 in co-silenced plants indicated that co-silencing significantly enhanced wheat susceptibility compared to single knockdown TaTLP1 or TaPR1 plants. The accumulation of reactive oxygen species (ROS) was significantly reduced in co-silenced plants compared to controls during Pt infection, which suggested that the TaTLP1-TaPR1 interaction positively modulates wheat resistance to Pt in an ROS-dependent manner. Our findings provide new insights for understanding the roles of two different PRs, TaTLP1 and TaPR1, in wheat resistance to leaf rust.

A rational molecule design strategy based on scaffold hopping was applied to discover novel leads, and then a series of novel pyrazole amide derivatives were designed, synthesized, characterized, and evaluated for their antifungal activities. Bioassay results indicated that some target compounds such as S3, S12, and S26 showed good in vivo antifungal activities; among them, S26 exhibited commendable in vivo protective activity with an 89% inhibition rate against Botrytis cinerea on cucumber at 100 μg/mL that is comparable to positive controls boscalid, isopyrazam, and fluxapyroxad. Microscopy observations suggested that S26 affects the normal fungal growth. Fluorescence quenching analysis and SDH (succinate dehydrogenase) enzymatic inhibition studies validated that S26 may not be an SDH inhibitor. Based on induction of plant defense responses testing, S26 enhanced the accumulation of RBOH, WRKY6, WRKY30, PR1, and PAL defense-related genes expression and the defense-associated enzyme phenylalanine ammonia lyase (PAL) expression on cucumber. These findings support that S26 not only displayed direct fungicidal activity but also exhibited plant innate immunity stimulation activity, and it could be used as a promising plant defense-related fungicide candidate.

Indole is a popular and functional scaffold existing widely in the fields of medicine, pesticides, spices, food and feed additives, dyes, and many others. Among indoles, 2-arylindole represents a particular and interesting subset but has attracted less attention for drug discovery. In this study, we report a general, practical one-pot assembly of a variety of 2-arylindole derivatives. To develop novel fungicide scaffolds, their fungicide activity was also evaluated. The bioassay results showed that many of the synthesized 2-arylindoles exhibited considerable fungicidal activities especially toward Rhizoctonia cerealis, and several demonstrated an inhibition rate of more than 90%. Notably, 4-fluoro-2-phenyl-1H-indole 6e was obtained with a broad spectrum of fungicidal activities, which showed excellent growth inhibition activities against R. cerealis, Rhizoctonia solani, Botrytis cinerea, Magnaporthe oryza, and Sclerotinia sclerotiorum with EC 50 values of 2. 31, 4.98, 6.78, 10.57, and 17.80 μg/mL, respectively. Preliminary fungicidal mode of action of 6e showed a significant inhibition effect on mycelial growth and spore germination. These results indicated that 2arylindoles as privileged scaffolds exhibited potential fungicidal activities that deserve further study.

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