A research project focused on long-term, high-tech results using gene editing technology and aimed at bolstering the industry’s fight against greening and beyond is underway and could have implications for all of Florida’s crops, not just citrus.
Dr. Heqiang “Alfred” Huo is an associate professor of ornamental plant breeding at the University of Florida and lead researcher of the Plant Transformation Team at the Crop Transformation Center (CTC) in Gainesville. Founded in 2023, the CTC develops research projects that focus on improvement across all major crops grown in Florida.
Huo’s team uses a comprehensive approach to understand and improve the genetics of ornamental and specialty crops, incorporating genetics, genomics, molecular biology and biotechnology to improve plant performance.
The CTC partnered with the Florida Department of Citrus and the Citrus Research and Development Foundation in Lake Alfred to focus on creating citrus varieties that can tolerate or resist citrus greening disease.
Huo’s background is mainly in ornamentals, and his extensive research has focused on plant transformation methodology and gene editing across many different species, including crops like tomatoes and lettuce, as well as ornamental plants like violets, petunias and marigolds.
The main barrier in gene editing, according to Huo, is twofold: First, how to deliver the CRISPR reagents into the plant cells, and how to regenerate those cells into whole plants.
There are several approaches to accomplishing this. The most widely used and reproducible, according to Huo, is Agrobacterium-mediated transformation. Viral vectors are another delivery method, though with a little less consistent result. Nanoparticle delivery is the third method, though it is still developing. “It helps to think of these delivery methods like vehicles: Agrobacterium is a big bus, while viral vectors are a smaller bus,” says Huo. “Nanoparticles are another type of carrier.”
When it comes to citrus, a woody perennial, and gene editing, though, there are several challenges, according to Huo.
First, while seedlings are easy to transform, they take years to fruit. “You won’t know if your edit worked for a long time,” says Huo. “And while mature trees are able to produce fruit faster, they are harder to transform and regenerate. Mature tissues carry internal microbes,” he says, which makes creating a clean culture difficult. Also, mature plant tissue struggles to regenerate shoots.
While citrus is a focal point in this research project, Huo points out the biggest challenge will be to create transgene-free gene-edited plants, crops that have modified genes, but contain no foreign DNA. Figuring out a consistent way of doing that with a process that works every time goes beyond specific plant types.
“We are not plant pathologists. We don’t discover the genes; we take genes identified by others and insert them into crops to develop the methodology and a pipeline that will enable real-world application,” he says. “We work in the middle. Our goal is to make gene editing accessible so any breeder or scientist can use the technology effectively.”