DEAD-box Protein SMA1 Activates Immunity Likely Through the Formation of Nuclear Condensates with EDS1 in Arabidopsis.

Plants have developed an elaborate immune system to effectively combat diverse pathogens, mainly through intricate signaling pathways. However, more studies will be required to have a better understanding of the activation mechanism of plant immune responses. Here, we report the biological function of SMA1, a nuclear-localized DEAD-box RNA helicase, in plant disease immunity. A point mutation (D634Y) of SMA1 in sma1-1 leads to autoimmunity, partially dependent on the nucleotide-binding leucine-rich repeat receptor protein SNC1. Furthermore, SMA1 interacts with the central immune regulator EDS1 in the nucleus. The intrinsically disordered region of SMA1 is crucial for the formation of SMA1-mediated nuclear condensates (SMNCs), consisting of SMA1 and EDS1. Notably, the formation of SMNCs is triggered by salicylic acid and pathogen infection. Additionally, the D634Y mutation in SMA1 promotes SMNC formation and EDS1 accumulation. Collectively, our findings highlight the significant role of SMA1 in regulating RNA metabolism and its contribution to plant immunity.