Iron-binding transferrins regulate immunity and reproduction via tissue-specific iron redistribution in Spodoptera exigua

Abstract

Transferrins are a multifunctional family of proteins that are essential for diverse physiological processes through their binding and transport of iron. Although previous studies have indicated that transferrins play crucial roles in insect antibacterial immunity and reproduction, the molecular mechanisms by which they regulate these essential processes remain poorly understood. Here, we identified and characterized transferrins in the beet armyworm, Spodoptera exigua (Hübner), an economically important agricultural pest, and elucidated their roles in innate immunity and reproduction. Four putative transferrin-coding genes were identified in the S. exigua genome, and structural analysis revealed that iron-binding domains were present exclusively in SeTsf1. Following infection with the entomopathogenic fungus Metarhizium anisopliae, SeTsf1 expression increased 3.2-fold, whereas iron levels decreased by 57.9 % in the hemolymph but increased by 51.6 % in the fat body. SeTsf1 knockdown significantly enhanced the susceptibility of S. exigua to M. anisopliae infection and abolished the hypoferremic response. Additionally, SeTsf1 silencing reduced egg production and hatching rates by 26 % and 28 %, respectively, and was accompanied by a 31 % decrease in ovarian iron content. Taken together, these findings demonstrate that SeTsf1 regulates immunity and reproduction through tissue-specific iron redistribution in S. exigua.