The role of reactive oxygen species and calcium signaling in antiviral defense in Arabidopsis
Plant viruses interfere with host signaling pathways, but it remains unclear how calcium (Ca2+) signaling, reactive oxygen species (ROS), and changes in the plasma membrane interact during viral infection. Here, we investigated how plantago asiatica mosaic virus (PlAMV) modulates host Ca2+ and ROS-associated signaling in Arabidopsis thaliana. Using live-cell imaging and the R-GECO1.2 Ca2+ sensor, we observed a rapid increase in cytoplasmic Ca2+ before the virus was detected, indicating that Ca2+ release occurs early in infection. Genetic analysis showed that GLR, CPK3, and CNGC, core components of Ca2+ signaling, limit PlAMV spread between cells, while the usual pattern-triggered immunity (PTI) co-receptors were not needed. This means that Ca2+-based antiviral restriction operates independently of PTI. With the plasma membrane-tethered and cytosolic HyPer7 biosensor, we found that ROS levels were lower inside infection foci in the inoculated leaves, but higher in nearby cells, respectively. The NADPH oxidases RBOHD and RBOHF, which produce ROS, slowed down the local viral propagation. The PM sphingolipid biosynthetic enzyme MOCA1 altered ROS patterns and reduced the viruss spread. Epistasis analysis revealed a functional interaction between RBOHD and MOCA1, suggesting that ROS signaling and plasma membrane sphingolipid homeostasis are interconnected in antiviral defense. Overall, our findings suggest that PlAMV triggers Ca2+ influx and ROS signaling at the plasma membrane, which induces sphingolipid reorganization and helps restrict the propagation of the virus. This study shows how Ca2+, ROS, and membrane sphingolipid signaling work together in plant antiviral immunity and points to possible ways to improve resistance to viruses.