Current advances in mechanisms of antiviral immunity

Plant viral diseases constitute a major driver of global crop yield losses annually, posing severe threats to agricultural productivity and food security. To counteract viral infections, plants have evolved a sophisticated multilayered immune system that integrates detection, signaling, and effector mechanisms. Core antiviral defenses encompass RNA silencing, ubiquitination-mediated degradation, autophagy, and phytohormone signaling pathways. Central to these defenses is the plant innate immune system, which operates through two interconnected tiers: Pattern-Triggered Immunity (PTI) and Effector-Triggered Immunity (ETI).PTI, initiated when cell surface-localized Pattern Recognition Receptors (PRRs) detect conserved Pathogen-Associated Molecular Patterns (PAMPs), triggers downstream signaling cascades. These include calcium influx, reactive oxygen species (ROS) bursts, and activation of mitogen-activated protein kinase (MAPK) pathways, collectively establishing broad-spectrum resistance. However, the extent to which plant viruses activate PTI remains debated. In contrast, ETI—mediated by intracellular Nucleotide-Binding Leucine-Rich Repeat (NLR) receptors—provides a potent antiviral mechanism. NLRs directly or indirectly recognize viral avirulence (Avr) effectors, eliciting a hypersensitive response (HR) characterized by localized programmed cell death (PCD) to restrict viral spread. Recent studies have elucidated the dynamic regulatory networks underpinning NLR-mediated immunity. Some NLRs function as sensors that detect viral effectors, while others act as helpers that amplify immune signals. Structural analyses reveal that NLR activation involves conformational changes, oligomerization into resistosomes, and recruitment of downstream signaling components. Some NLRs employ the guard hypothesis, indirectly sensing viral effectors by monitoring host proteins disrupted during infection. Importantly, NLR activity is tightly regulated at transcriptional and post-translational levels to mitigate fitness costs, as constitutive NLR activation can impair plant growth and development. Furthermore, NLRs coordinate with other antiviral pathways and host factors to orchestrate integrated immune responses. Harnessing NLR-based strategies holds transformative potential for crop improvement. Advances in CRISPR/Cas9-mediated genome editing and molecular breeding enable precise engineering of NLR genes to enhance antiviral specificity and durability. For instance, artificial evolution approaches have expanded NLR recognition spectra, while gene pyramiding—combining NLRs with other resistance mechanisms—creates robust multilayered defenses. These innovations are accelerating the development of crops with broad-spectrum, climate-resilient viral resistance.This review synthesizes current insights into plant antiviral immunity, with a focus on key pathways that have garnered significant attention in plant-virus interaction research. These include RNA silencing, ubiquitination-mediated protein degradation, autophagy, and phytohormone signaling networks. Notably, we emphasize the NLR-mediated antiviral immunity, elucidating its downstream molecular mechanisms and structural underpinnings. Here, we systematically analyze the crosstalk between NLR-mediated immunity with other antiviral pathways, as well as host factors critical for immune coordination. Key aspects of NLR activation mechanisms—such as conformational switching, resistosome formation, and effector recognition strategies. Furthermore, this work highlights emerging biotechnological strategies for deploying NLRs in crop breeding programs. CRISPR/Cas9-driven precision editing, artificial NLR evolution, and gene pyramiding approaches demonstrate substantial potential to mitigate viral disease burdens and enhance global food security. Future research should prioritize NLR diversification in wild crop relatives, decoding effector-NLR interaction networks, and engineering resistance strategies resilient to viral evolution. By bridging foundational discoveries with agricultural innovation, NLR-driven approaches will be critical for sustainable crop production amid climate change and emerging viral threats.