By Ryan Wu

Anne Simon, a professor of cell biology and molecular genetics, spoke to students at Milkboy Arthouse Tuesday evening about the effects of a citrus plant disease and how her research team is tackling it.

This was one of the lectures in a series called “Science on Tap” that is put together by the college of computer, mathematical and natural sciences. They’ve run their lectures monthly since Feb. 2018 to explore the latest discoveries in science and technology.

Simon, who is also a member of the American Association of Microbiology, said the citrus industry is dealing with a new phenomenon known as ‘citrus greening disease,” which was first discovered in China over a decade ago. Citrus plants infected with the disease may produce sour, green fruits that are unmarketable and the trees themselves die out in a few years as the leaves are deprived of nutrients and become dry.

As a result of the disease’s spread, production of citruses is now limited to the edge of the country. It has since spread to other regions such as India, Africa, Mexico, Florida and California.

“Every single citrus tree in Florida is infected and half are dead. The entire citrus industry in Florida is about to go under,” Simon said.

According to Simon, if the disease isn’t reigned in, the only citruses in 10-15 years will be grown in greenhouses. The price of these citruses could spike to over $20 per pound, compared to around $5 today.

She added that not only will the global production of citruses be affected, but many other fruits are at risk of a lack of supply.

“Imagine a future where there’s no orange juice, no margarita, no lemon. That’s an ending we don’t want that might occur,” she said.

Simon said that what caused the greening disease is a combination of a psyllid insect and the trees’ own immune system. Psyllids sit on the tree’s leaves and inject the candida bacteria into its vines. The tree then develops a defense against the bacteria, secreting substances that cut off the spread of nutrients throughout, thereby killing itself.

“Citrus trees aren’t the brightest trees in the forest, it’s the trees that are killing themselves,” she added.

The extent of the infection, according to Simon, has required agencies like the USDA to spend over $400 million to combat the disease.

Many measures implemented by the USDA caused either drug resistance or higher temperatures and more bacteria.

Simon and other researchers at the Department of Cell Biology and Molecular Genetics decided to find a virus-like RNA agent that wouldn’t harm the trees but could still kill off bacteria secreted by psyllids by changing their gene expressions, and hopefully at the outset of an existing infection, reverse the damages done.

“If we can prevent the tree from making its counterpart, it would ignore the bacteria and be perfectly fine,” she said.

While conducting their research, Simon said the team encountered problems such as lack of access to the right proteins that help the RNA agent reach the vine of the plants. Fortunately, after collaboration with scientists at University at California, Riverside in 2011, the team was able to find the right type of RNA structure as well as the proteins that enter the cells and replicate themselves. 

“It’s associated with no or very mild symptoms, it’s only limited to the vine, exactly where the bacteria is,” she said.

Although this new technique is still a work in progress, their discovery can potentially be applied to diseases other than citrus greening, such as one that’s killing olives in Italy and another called “fire blight,” which affects apple and pear trees in the U.S. state of Washington. 

Alanna Anderson, a sophomore linguistics major, said she didn’t know much about the citrus greening diseases before the talk, but she thought it was a good opportunity to learn more about the latest research in biology. She said the potential increase in citrus prices was interesting to hear because her mom is a regular consumer of them.     

“She’s going to be upset when the prices of citrus go up,” Anderson said.

Matthew Jackson, a senior biochemistry major, said he was interested in the talk because of the biology classes he took related to the topic. What made the lecture enjoyable for him was the relaxed setup and Simon’s logical presentation. He said the professor’s implementation of virus-like agents was eye-opening, as this process isn’t something most people are aware of.

“Once you think you understand something, there’s always more to learn,” Jackson added.