Nav: Home

Scientists identify two new proteins connected to plant development

May 19, 2017

COLLEGE STATION -- The discovery of two new proteins could lead to better ways to regulate plant structure and the ability to resist crop stresses such as drought, thus improving agriculture productivity, according to researchers at Texas A&M AgriLife Research.

The two proteins, named RICE1 and RICE2, are described in the May issue of the journal eLife, based on the work of Dr. Xiuren Zhang, AgriLife Research biochemist in College Station.

Zhang explained that DNA contains all the information needed to build a body, and molecules of RNA take that how-to information to the sites in the cell where they can be used.

But cells make their own RNA, and they only need so much in order to develop properly and respond well to their environment. So plants make an even smaller molecule, called microRNA or miRNA, that removes the extra RNA and stop it from making proteins. That process is called RNA silencing.

Understanding silencing is important because researchers can use the technique to help a plant overcome barriers to growth or ability to deal with unfavorable environments by tweaking the amount of RNA.

"One key player in RNA silencing is the multi-component complex called RISC (RNA-induced Silencing Complex), which contains microRNA and enzymes called AGOs," Zhang said. "MicroRNA starts as twins, so to speak, but one of the twins leaves and disappears when AGO protein moves in."

Once the microRNA has identified its RNA target for silencing, the AGOs cut the RNA into two pieces, known as the 5-prime and 3-prime cleavage fragments.

"These fragments are basically the starting and ending sections of RNA molecules. But, the two resulting fragments must be cleared away rapidly, so the RISC can move on to the next target," he said.

"It's like eating in a restaurant during rush hour," Zhang explained. "You eat quickly and leave. Then the waitstaff clears the table and resets it to serve the next guests."

Researchers have known how the 3-prime cleavage fragment was removed but were less clear how the 5-prime cleavage fragment was dealt with, he said.

"What was known was that the 5-prime cleavage fragment is marked with a chemical called uridine," Zhang said. "Somehow, uridine tells the RISC, which holds the miRNA, that this fragment needs to be destroyed."

Using proteomic analysis, a powerful biochemical approach, Zhang and colleagues deciphered the constituents of one kind of RISC in arabidopsis, a model plant often used in research. They found RICE, or RISC-Interacting Clearing Exoribonuclease, proteins there.

Further study of the biochemical features of RICE proteins showed them to be enzymes that degrade RNA. Using crystallography, Dr. Pingwei Li, AgriLife Research biochemist in College Station, found that RICE1 has a ring-like shape with six identical molecules.

"This ring-shape structure is very important because the protein can not survive if the ring-shape is disrupted," Li said. That would lead to problems during the development of the plant.

Zhang and colleagues then analyzed the shape of RICE1 and identified its 'active' region, which is responsible for degrading the RNA fragments, hidden on the adjacent site of two RICE molecules.

"When these active regions were blocked, the microRNA levels were low, but the 5-prime cleavage fragments that are marked with uridine were high," he said. "Also, the RISC complex could not work properly, which led to problems during the plant growth and development."

These results suggest that RICE proteins degrade 5-prime cleavage fragments modified with uridine to keep RISC alive.

RICE proteins are similar in plants and animals, Zhang said, so it is likely their counterparts in humans will have a similar role to the plant proteins and thus be important for development in the human body.

Zhang said the next challenge will be to explore how RICE proteins work in more detail, which may lead to new ways to manipulate the efficacy of RISC and the levels of microRNAs to alter organism architecture and to improve stress tolerance in biotechnological applications.
-end-
This study was supported by a National Science Foundation CAREER grant.

Texas A&M AgriLife Communications

Related Microrna Articles:

Researchers uncover key role for microRNA in inflammatory bowel disease
An international team of researchers has discovered that a microRNA produced by certain white blood cells can prevent excessive inflammation in the intestine.
MicroRNA may reduce stroke risk
The molecule microRNA-210 stabilises deposits in the carotid artery and can prevent them from tearing.
MicroRNA treatment restores nerve insulation, limb function in mice with MS
Scientists partially re-insulated ravaged nerves in mouse models of multiple sclerosis (MS) and restored limb mobility by treating the animals with a small non-coding RNA called a microRNA.
Choreographing the microRNA-target dance
Molecular biologists at UT Southwestern Medical Center were able to uncover a new mechanism that choreographs a complex molecular dance by applying the latest in gene editing technology combined with a traditional method of making a microRNA target produce a fluorescent green protein.
A chemical-biological strategy for microRNA target identification
Chen-Yu Zhang's group at Nanjing University reports photo-clickable miRNAs as probes for intracellular target identification of miRNAs.
Down regulation of microRNA-155 may underlie age-related hypertension
In this issue of JCI Insight, researchers led by Iris Jaffe of Tufts Medical Center provide evidence that age-related reductions of a microRNA (miR-155) underlie age-associated hypertension.
Loss of a microRNA family, let-7, found key in neuroblastoma
A study led by researchers at Dana-Farber/Boston Children's Cancer and Blood Disorders Center, finds that a microRNA called let-7 plays a central role in curbing neuroblastoma and could focus efforts to find a targeted, nontoxic alternative to chemotherapy.
Mechanisms & therapeutic targets of microRNA-associated chemoresistance in epithelial ovarian cancer
This review provides an overview of current therapeutic targets of miRNA-associated chemoresistance in EOC and illustrates the therapeutic potential and molecular mechanisms by which miRNAs influence the development and reversal of chemoresistance.
MicroRNA may help control arterial thrombosis
In a new study published online this week in The FASEB Journal, a Brigham and Women's Hospital research team investigated the role of miR-181b in blocking the development of arterial thrombosis.
Restoring chemotherapy sensitivity by boosting microRNA levels
By increasing the level of a specific microRNA (miRNA) molecule, researchers have for the first time restored chemotherapy sensitivity in vitro to a line of human pancreatic cancer cells that had developed resistance to a common treatment drug.

Related Microrna Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Jumpstarting Creativity
Our greatest breakthroughs and triumphs have one thing in common: creativity. But how do you ignite it? And how do you rekindle it? This hour, TED speakers explore ideas on jumpstarting creativity. Guests include economist Tim Harford, producer Helen Marriage, artificial intelligence researcher Steve Engels, and behavioral scientist Marily Oppezzo.
Now Playing: Science for the People

#524 The Human Network
What does a network of humans look like and how does it work? How does information spread? How do decisions and opinions spread? What gets distorted as it moves through the network and why? This week we dig into the ins and outs of human networks with Matthew Jackson, Professor of Economics at Stanford University and author of the book "The Human Network: How Your Social Position Determines Your Power, Beliefs, and Behaviours".