The Solanaceae-conserved peptide NbSolP9 enhances tobacco resistance to Botrytis cinerea by regulating nicotine metabolism

Solanaceae peptides (SolP) are conserved small secreted immune peptides widely distributed in Solanaceae species, yet the association between their immune functions and crop quality traits remains elusive. In this study, systematic genome-wide mining and sequence alignment across multiple Solanaceae species identified a highly conserved core sequence of SolP peptides (VTSNALALINQFAA), and the corresponding SolP peptide in Nicotiana benthamiana was designated NbSolP9. Exogenous application of the chemically synthesized NbSolP9 peptide triggered pattern-triggered immunity (PTI) in N. benthamiana and significantly enhanced the plant's resistance to Botrytis cinerea. Consistently, transient overexpression of the ProNbSolP9 gene in N. benthamiana similarly enhanced resistance to B. cinerea. Furthermore, exogenous NbSolP9 application significantly increased the nicotine content in N. benthamiana. Targeted silencing of quinolinate phosphoribosyltransferase 2 (QPT2) via VIGS confirmed that nicotine accumulation mediates the NbSolP9-triggered PTI responses. These findings provide important theoretical support for developing SolP-based green breeding strategies and biopesticides to improve crop pathogen resistance.