Tomato spotted wilt orthotospovirus (TSWV) severely damaged agricultural production in many places around the world. It is generally believed that TSWV transmits among plants via their insect vector. In this study, we provide evidence on the seed-borne transmission of TSWV in pepper (Capsicum annuum L.) plants. RT-PCR, RT-qPCR, and transmission electron microscopy data demonstrate the seed transmission ability of TSWV in peppers. Endosperm, but not the embryo, is the abundant virus-containing seed organ. TSWV can also be detected in the second generation of newly germinated seedlings from virus-containing seed germination experiments. Our data are useful for researchers, certification agencies, the seed industry, and policy makers when considering the importance of TSWV in vegetable production all over the world.

Nucleotide-binding leucine-rich repeat receptors (NLRs) function as core components of innate immunity in both plants and animals. In animals, NLR activation initiates caspase-mediated immune signaling. In contrast, plants lack caspases but instead contain metacaspases (MCAs/MCs), yet their role in antiviral immunity and whether they interface with NLR signaling remain largely unexplored. Here, we demonstrate that cleavage of the conserved immune regulator Bcl-2-associated athanogene 3 (BAG3) by metacaspase 4 (MCAIIa/MC4) induces cell death and activates antiviral immunity in plants. Upon Begomovirus infection, MC4 cleaves BAG3 to release its N-terminal functional domain (BAG3-N) from autoinhibition. BAG3-N assembles into oligomers and induces cell death, effectively inhibiting viral replication. This signaling also interfaces with NLR networks in certain plant species. Viral replication-associated proteins (Reps) counteract this defense response by binding to BAG3-N, highlighting an evolutionary arms race between plants and viruses. Evolutionary analyses reveal that a lysine substitution at position 50 of BAG3 confers its ability to induce cell death in angiosperms. These findings identify BAG3 as a conserved immune regulator linking metacaspase activation to antiviral defense, providing a mechanistic basis for engineering crops with enhanced resistance to insect-borne viruses.