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ViewAttendees 6

TECHNICAL SESSION: Molecular Plant-Microbe Interactions

Spinach defensin peptides confer tolerance to citrus greening and potato zebra chip diseases

Sunday, August 3, 2025
2:00 PM - 2:15 PM HST
Location: Ballroom B/C
Abstract Text:

Citrus greening or Huanglongbing, and potato zebra chip are devastating diseases affecting worldwide citrus and potato production. The diseases are transmitted by insect vectors and are associated with fastidious (unculturable), phloem-limited bacteria, Ca. Liberibacter spp. Defensins are short (~40 to 50 amino acids) basic, cysteine-rich peptides integral to the innate immune system in plants, animals, and insects and possess broad-spectrum inhibitory activity against bacterial and fungal pathogens. Here, we tested whether expressing defensins from spinach in citrus and potato can confer tolerance to Ca. Liberibacter spp. Given the unculturable nature of Ca. Liberibacter spp., efficacy evaluation of two spinach defensins (SoAMP1 and SoAMP2), was first performed using the ex vivo microbial hairy root system. Both SoAMP1 and SoAMP2 demonstrated significant antimicrobial activity against Ca. Liberibacter spp. in citrus and potato hairy roots. In in vitro cytotoxicity assays using a culturable surrogate bacteria, Liberibacter crescens, spinach defensins disrupted bacterial cell membranes and permeability, leading to mortality. Furthermore, heterologous expression of SoAMP1 and SoAMP2 in potatoes and citrus using genetic engineering or viral vector-mediated expression conferred tolerance to Ca. Liberibacter spp. and significantly improved the yield of infected plants. In conclusion, the naturally occurring spinach defensin peptides could be used as crop protection for managing citrus greening, potato zebra chip, and related plant diseases.