DURHAM, N.C. -- Ever since tiny bits of genetic material known as microRNA were first characterized in the early 1990s, scientists have been discovering just how important they are to regulating the activity of genes within cells.
A new study now shows that microRNAs don't just control the activity of genes within a given cell, they also can move from one cell to another to send signals that influence gene expression on a broader scale.
Researchers at the Duke Institute for Genome Sciences & Policy (IGSP), in collaboration with groups at the Universities of Helsinki and Uppsala and the Boyce Thompson Institute for Plant Research at Cornell University, made the discovery while working out the intricate details of plant root development in Arabidopsis, a highly-studied mustard plant. Although they still don't know exactly how the microRNAs travel, it appears that this mobility allows them to play an important developmental role in sharpening the boundaries that define one plant tissue from another.
"To our knowledge, this is the first solid evidence that microRNAs can move from one cell to another," said Philip Benfey, director of the Duke IGSP Center for Systems Biology.
The findings, which appear in an advanced online publication of the journal Nature on April 21, add microRNA to the list of mobile molecules, including hormones, proteins and other forms of small RNA, that allow for essential communication between cells in the process of organ development.
They also add a new element to the already complex interplay in Arabidopsis roots between two proteins, known as Scarecrow and Short-root, that Benfey's team had described in earlier work (http://www.dukenews.duke.edu/2007/04/short-root._print.ht). Those proteins interact and restrain one another to allow the assembly of a waterproofing layer of cells that ultimately enables plants to con
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