Efficient Production of 14-Membered Macrolides by the Endophytic Fungus Colletotrichum gloeosporioides GLL-7 and Their Insecticidal Activity against Diaphorina citri.

The citrus psyllid (Diaphorina citri) vectors Huanglongbing. Overuse of insecticides causes resistance and pollution, necessitating safer alternatives. Bioactivity-guided fractionation of the fungus Colletotrichum gloeosporioides GLL-7 yielded two macrolides: Sch725674 and Gliomasolide H (GLH). Sch725674, a major metabolite produced at 0.035 g per gram of culture medium, is easily obtained via methanol trituration. GLH is a novel macrolide; its structure was elucidated by spectroscopy and confirmed by chemical synthesis. GLH exhibited contact toxicity (24 h LC50 = 0.129 mg/mL) against D. citri; it damaged wax layer, decreased hydrophobicity, lowered nymph emergence rates, and shortened adult body length. Metabolomics, qRT-PCR, and molecular modeling analyses indicated that GLH possibly targets phospholipid metabolism, disrupting lipid homeostasis and wax formation. In addition, GLH exhibited low toxicity to various nontarget organisms. Thus, GLH is a promising lead compound for controlling D. citri, and C. gloeosporioides GLL-7 is a valuable bioresource for producing unusual macrolides.