New role of tiny RNA in plant growth

Biological researchers at Rice Institute, MIT found microRNA plays an essential role in gene expression. Discovered for the first time in previous years, scientists around the world are racing to find and study microRNAs - small pieces of RNA that regulate gene expression in animals and plants.

(Photo: sciencedaily)

It is believed that hundreds of microRNAs exist in each animal and plant species, but few of their functions are known.

According to a recent study by biologists from Rice University and Whitehead Institute for Biomedical Research at the Massachusetts Institute of Technology, one of the first groups to discover microRNA in plants, this RNA, called miR164, plays survival in the full development of flowers, leaves and stems of Arabidopsis.

"We already know that miR164 is present in some other flowering plants and in rice. This gene is preserved throughout the process of over 250 million years of evolution." Bonnie Bartel, associate professor of biochemistry and cell biology at Rice, co-author of the study, said. "Our study has discovered that this small piece of RNA is an essential regulator of the cycle. The molecular circuitry controls the development of the basic organs of plants'.

The study included experiments on three Arabidopsis strains : one normal (or wild-type) and two mutant strains created in the laboratory. With the first mutant line, miR164 is 'super-expressed' or produced in much larger quantities than usual. In the second mutant line, the target gene miR164 is resistant to regulation by miR164, allowing researchers to observe results without miR164 conditioning.

The researchers found that in both cases the leaves and flowers developed abnormally. When the regulation of miR164 loss of the target gene is lost, the plant organs are produced in abnormal numbers. For example, there may be too many or too few petals, the surrounding shell is like a rice hull that protects the flower when hatched. When there are too many miR164, the organs are combined. Petals do not separate completely, for example, stamens grow together into a mass.

RNA is a substance that translates the genetic code of DNA into protein. Structurally, RNA is a sequence of phosphate, sugar and nucleotide molecules. The most common form of RNA, the mRNA contains thousands of nucleotides and is the genetic plan used by cells to incorporate amino acids into proteins.

Smaller microRNAs , only about 20 nucleotides long. All microRNAs "regulate down" the production of certain proteins by disrupting mRNA in a number of ways.

One of the mysteries is why microRNAs are conserved for so long in such an evolutionary process. They are thought to have existed before animals and plants split into two separate evolutionary paths. By studying the function of particular microRNAs, scientists hope to be able to answer basic questions about how and why they evolve, as well as gain certain knowledge. Used in some new agricultural and medicine technologies.

Arabidopsis, the universal genetic model, one of the most studied plants, is the first plant to discover microRNA and nearly 100 microRNAs have been identified in these species.

The research was supported by the National Institutes of Health, G. Harold and Leila Y. Mathers, the Robert A. Welch Foundation, and Alexander and Margaret Stewart. Co-authors are David Bartel, associate professor of biology at Whitehead Institute and MIT; Allison Mallory, postdoctoral researcher at Whitehead; and Diana Dugas, graduate student at Rice.

Nguyen Xuan Hung