Abstract Plant elicitor peptides (Peps) are conserved damage-associated molecular patterns (DAMPs) that regulate plant immunity and growth, but their roles in citrus, a major economically important fruit crop, remain underexplored. A pangenome analysis of 15 Aurantioideae species identified 17 PRECURSOR OF PEP ( PROPEP ) genes encoding 22-amino-acid mature Peps with conserved receptor-binding motifs. Expression analysis demonstrated that Citrus sinensis PROPEP ( CsPROPEP ) and its receptor CsPEPR were significantly modulated by infection with Xanthomonas citri subsp. citri ( Xcc ), the causal pathogen for citrus canker disease and by phytohormones, including jasmonic acid (JA) and salicylic acid (SA). Supplementing the regeneration medium with 0.01 nM CsPep boosted shoot regeneration efficiency during genetic transformation by 2.43- to 3.21-fold in Citrus sinensis . Likewise, adding CsPep to the Agrobacterium rhizogenes infection solution enhanced root development in stem cuttings, increasing lateral root numbers by 2.23- to 2.98-fold and maximum root length by 1.74- to 2.59-fold. This growth-promoting effect was conserved across other citrus species, including pummelo and lemon. Furthermore, both exogenous application of CsPep and transient overexpression of CsPROPEP activated citrus immune responses, conferring enhanced resistance to citrus canker. These findings highlight the dual role of CsPep in activating immune defenses and promoting regeneration, bridging a critical gap in DAMP peptide signaling in citrus. Our findings offer a peptide-based strategy for sustainable canker management and improved genetic transformation efficiency.
Zhang et al. (Wed,) studied this question.