Make Transgenic Citrus Lines with Robust Huanglongbing Tolerance
Posted August 2025
Researchers: Ozgur Batuman, Zhonglin Mou, Eric Triplett, Ricky Telg, Shouling Xu
Contact: Ozgur Batuman, UF/IFAS SWFREC obatuman@ufl.edu
Summary:
Plants use various defense pathways to combat pathogens. The jasmonic acid signaling pathway is essential for resistance against some pathogens and pests, while the salicylic acid (SA) signaling pathway provides resistance or tolerance to other pathogens such as Candidatus Liberibacter asiaticus (CLas). Our previous research produced transgenic huanglongbing (HLB)-tolerant ‘Hamlin’ trees by overexpressing citrus plants’ positive immune regulators (i.e., SA signaling pathway). These transgenic ‘Hamlin’ trees expressing the model plant AtNPR1 gene have shown consistent and robust tolerance to HLB through multiple generations of graft-propagated sibling plants. Despite high levels of AtNPR1 protein in the leaves of these transgenic plants, minimal accumulation occurs in the fruit pulp and juice. Importantly, any residual AtNPR1 in the fruit can be rapidly broken down by human digestive enzymes such as pepsin and trypsin in the stomach and intestines, ensuring that the transgenic citrus remains safe for consumption. The primary objective of this project is to scale up the production of these promising transgenic lines for large-scale field trials at 2 prominent locations in Florida. We are now gathering comprehensive data to support plant patent applications and secure regulatory approvals from the USDA, EPA, and FDA. Furthermore, we will provide clean budwood resources to the industry through the FDACS/DPI Bureau of Citrus Budwood Registration Program, facilitating widespread adoption of these advanced transgenic citrus varieties.
Take Home Message:
- Transgenic ‘Hamlin’ producing new proteins (AtNPR1) provide tolerance to HLB, and are now being trialed in the grove.
- Their field performance will allow us to gather key information needed for securing regulatory permits for the industry.
- Low protein levels in fruit and easily broken down by digestive enzymes make them safe for consumption.
