Calcium signaling in soybean-virus interactions: emerging roles of calcium sensors in antiviral and environmental stress responses

Soybeans (Glycine max) in the field face biotrophic and abiotic stresses simultaneously. Although calcium (Ca2+) signaling mediates plant stress adaptation and links perception to downstream transcriptional and metabolic reprogramming, its roles in integrating viral defense in soybean remain under-investigated. Consequently, most soybean antiviral research has focused on R genes and RNA silencing rather than on the calcium signaling hubs that may coordinate and fine-tune these defense pathways. Here, we propose a calcium-centered framework for understanding soybean-virus interactions, with an emphasis on the soybean mosaic virus (SMV). We summarize the soybean calcium signaling modules including calcineurin B-like protein (CBL)-CBL-interacting protein kinase, calcium-dependent protein kinases, and calmodulins/calmodulin-like proteins, which are key regulators of abiotic stress tolerance in soybean; however, their direct roles in antiviral defense remain largely unexplored. Recent transcriptomic and weighted gene co-expression network analysis studies have identified Ca2+-linked nodes embedded in reactive oxygen species, salicylic acid/jasmonic acid and mitogen-activated protein kinase networks, which are likely to modulate basal and R gene-mediated resistance. Insights from other plant-virus systems further show that how viruses have evolved sophisticated counter-strategies to subvert these Ca2+-mediated host defenses. Emerging models in Nicotiana benthamiana and Arabidopsis demonstrate how viral proteins manipulate calcium hubs to suppress oxidative bursts and RNA interference machinery. Despite the challenges posed by the paleopolyploid nature of the soybean genome and the technical hurdles of function validation, this review emphasizes that deciphering the calcium-dependent pathways in the soybean-SMV pathosystem is essential for engineering broad-spectrum, durable virus resistance and ultimately contributing to sustainable crop protection.