CgFre2 contributes to ferric reductase activity, growth and pathogenicity in Colletotrichum gloeosporioides.

Ferric reductases are oxidoreductases that catalyze the reduction of environmental Fe³ ⁺ to bioavailable Fe² ⁺ and mediate cellular iron uptake and metabolism. However, the specific biological functions of ferric reductases in Colletotrichum gloeosporioides have not been fully characterized. In this study, 15 ferric reductase-like proteins were screened from the genome annotation of C. gloeosporioides, and CgFre2 was selected for further functional characterization. Targeted deletion of CgFre2 resulted in reduced mycelial growth and a sharp decrease in conidiation. Further observation of conidial development showed delayed conidial germination and an increased incidence of abnormal appressorium formation, which impaired the proper morphogenesis of infection structures and thereby significantly attenuated the pathogenicity of the strain on chili peppers. Moreover, the expression levels of cell wall-related genes were downregulated in the CgFre2 deletion mutant, which exhibited impaired cell wall integrity and hypersensitivity to oxidative stress. Meanwhile, the expression levels of ferric reductase-like genes CgFre3, CgFre6, CgFre11, CgFre13, and CgFre15 were markedly upregulated in the CgFre2 mutant, whereas ferric reductase activity was reduced to 48% of the WT level. Notably, exogenous Fe³ ⁺ supplementation restored infection structure formation and pathogenicity on pepper leaves. Collectively, these findings reveal the biological function of ferric reductase CgFre2 and provide a theoretical basis for developing iron‑targeted green control strategies against pepper anthracnose.