Moderately ectopic expressing NLP27 in potato confers high disease resistance without yield penalty

A 27-aa peptide coding sequence NLP27 was moderately overexpressed in potato, conferring enhancing plant resistance to Phytophthora infestans and Streptomyces scabies infection without yield penalty through plant immunity promotion. The conserved short peptides derived from pathogen effectors can stimulate plant innate immunity response against pathogens through exogenous application. However, it remains to be explored whether the ectopic expression of these peptides in plants can trigger plant defense responses and affect plant growth. Here, we modified the nucleotide sequence of conserved 27-amino acid peptide derived from Verticillium dahliae NLP1 gene and ectopically expressed in potato, generating transgenic plants designated as NLP27 lines. Based on inoculation analysis, three transgenic lines with moderate NLP27 expression levels, PT1, PT6, and PT7, exhibited significantly higher resistance to Phytophthora infestans and Streptomyces scabies compared to the control plants transformed with the empty vector, the disease resistance is enhanced by 53.6% to 85.7%. Staining and biochemical analyses revealed that the accumulation of O₂^- and H₂O₂ and callose deposition were significantly higher in the three transformants compared to the control. The transcriptional levels of eight defense-related genes-involved in the SA (PR1, PR5, and PAL1) and JA (AOS1, PDF1.2, and LOX1) pathways, or associated with basal defense responses (WRKY8 and NAC2)-were significantly upregulated in the three transgenic lines compared to the control. Extremely high expression levels of NLP27 in potato transformants inhibited plant growth, leading to yield reduction. However, moderate expression of NLP27, as in lines PT1, PT6, and PT7, increased resistance to potato late blight and scab without yield penalty. In summary, this study provides insight into the novel mechanisms and management in balancing defense and growth in potatoes ectopically expressing the NLP27 short peptide.