Citrus Tristeza Virus (CTV) Expressed Antimicrobial Peptides Induce Tolerance to Huanglongbing
Posted August 2025
Researchers: Choaa El Mohtar, Kranthi Mandadi, James Borneman
Contact: Choaa El Mohtar, UF/IFAS CREC mohtarc@ufl.edu
Summary:
Huanglongbing (HLB) disease associated with Candidatus Liberibacter asiaticus (CLas) is devastating the citrus industry in Florida. CLas is not in pure culture yet, and its phloem tissue tropism makes identifying therapeutics to target the bacteria directly very challenging both in vitro and in vivo. As citrus tristeza virus (CTV) and CLas colocalize to the phloem tissue of citrus without interacting synergistically, CTV is being used as a bio-delivery tool to identify therapeutics to manage huanglongbing. One of the most promising venues is using CTV to target CLas directly via naturally occurring small antimicrobial peptides (AMPs) that are part of many organisms’ defense strategy against invading pathogens. AMPs usually have a short half-life and are released only upon recognition of pathogen infection. We have engineered CTV vectors to differentially express the active form of around 100 AMPs independently. Most sweet orange seedlings infected with HLB via ACP showed symptoms similar to healthy control plants or wild type CTV infected plants. However, sweet orange citrus seedlings infected with few CTV-AMP overexpressing vectors showed early disease symptoms on some branches under high inoculum pressure in greenhouse assays but later recovered. Despite recovery, qPCR revealed that these plants are clearly infected with CLas. Further, field testing in Florida revealed improved yield as compared to controls over two years in field assays. Currently, we are working to improve the efficacy of AMPs via different strategies.
Take Home Message:
- CTV is a faster tool to identify therapeutics against HLB than transgenic or CRISPR strategies.
- CTV expressed antimicrobial peptides induce tolerance to HLB and improve yield.
- Working to improve the efficacy of AMPs for better tolerance and yield improvement.
