The NbCBP1-NbSAMS1 Module Promotes Ethylene Accumulation to Enhance Nicotiana benthamiana Resistance to Phytophthora parasitica Under High Potassium Status

Potassium (K) fertilization is crucial for plant resistance to pathogens, but the underlying mechanisms remain unclear. Here, we investigate the molecular mechanism by which the addition of K promotes resistance inNicotiana benthamianatoPhytophthora parasitica. We found thatN. benthamianawith high K content (HK, 52.3 g/kg) produced more ethylene in response toP. parasiticainfection, compared toN. benthamianawith low-K content (LK, 22.4 g/kg). An exogenous ethylene application effectively increased resistance in LKN. benthamianato the level under HK status, demonstrating the involvement of ethylene in the HK-associated resistance inN. benthamiana. Further, transcriptome analysis showed thatNbSAMS1, encoding ethylene biosynthesis, was induced to upregulateP. parasiticaabout five times higher in HK than in LKN. benthamiana. NbSAMS1overexpression enhanced resistance in LK plants, whereasNbSAMS1silencing reduced resistance in HK plants, confirming its importance in conferring resistance. Furthermore, we identified a calcium-binding protein, NbCBP1, which interacted with NbSAMS1, promoting its expression in HKN. benthamiana.SilencingNbCBP1compromised resistance in HKN. benthamiana, whereas its overexpression improved resistance in LKN. benthamiana. Notably, NbCBP1 protected NbSAMS1 from degradation by the 26S proteasome, thereby sustaining ethylene accumulation in HKN. benthamianain response toP. parasiticainfection. Thus, our research elucidated some mechanisms of the NbCBP1-NbSAMS1 module associated with disease resistance in HKN. benthamiana.