DNA is the genetic material that determines the characteristics of plants and animals. Using CRISPR gene editing, researchers altered the characteristics of rice plants. | Creative Commons Photo by Pixabay

By Cara Penquite | Bond LSC

A tickle in the throat, a stuffy nose, congestion . . . the tell-tale signs of a cold are familiar to most, and many know that with enough rest, the immune cells on standby in the human body will destroy any invaders. But what happens when plants get sick?

The Bing Yang Lab from the Bond Life Sciences Center at the University of Missouri studied this question with the Reuben Peters lab at Iowa State University by analyzing the purpose of gene clusters in rice. Along with the Zhaohu Li lab at China Agricultural University, the researchers — utilized CRISPR gene editing to determine the function of certain gene clusters in rice.

“I thought this could be something very important,” Yang said, “We can take out a huge amount of DNA to see if the gene cluster could play a role in this resistance [to disease].”

CRISPR – a gene editing tool – allows the researchers to change the DNA of the rice plants by removing sections of genetic code, known as gene clusters. By removing the cluster, scientists can see what breaks in the plant, thus identifying each cluster’s role in the plant’s health.

“These were what we termed biosynthetic gene clusters. They have unrelated genes that are close together, their physical proximity on a chromosome, and they all act in one single pathway to make a small family of natural products,” Peters said.

The scientists compared unedited rice plants with rice plants missing the gene clusters, and they determined that those without the gene clusters had decreased resistance to certain diseases. This was due to the decreased production of antimicrobial — or pathogen fighting — natural products.

The genes code for enzymes that create labdane-related diterpenoids — natural products responsible for protecting plants from infection, termed phytoalexins — a defense response.

The loss of these compounds made the plants less resistant to disease. While humans have mobile cells that can travel to pathogens through the immune system, plants rely on local chemical responses to fight off invaders.

“They’ll recognize components of the fungal cell wall, or they’ll interact with specific proteins from the fungus or the bacteria, [and] that triggers what we consider to be an immune response,” Peters said. “They have to rapidly make these compounds in what would otherwise be a general photosynthetic cell or just an epidermal cell on the surface of the leaf.”

By identifying which genes produce certain chemicals, the researchers have a greater understanding of the plant immune response, and they can manipulate the genetics of the plants to create stronger immune responses.

“We can fine tune those genes, which could increase the [protections] and make the plant more resistant to the pathogen,” Yang said.

Peters suggested since the scientists know which genes code for these proteins, they can make the proteins and create an antibiotic to prevent infections in crops and livestock.

“We do think that some of these compounds are going to be important for potential pharmaceutical activity,” Peters said. “Not necessarily the ones in rice, but related compounds, and that’s another reason we studied this.”

This research published online in New Phytologist October 16, 2021, under the title “Dissecting the labdane-related diterpenoid biosynthetic gene clusters in rice reveals directional cross-cluster phytotoxicity.”