Though composed of only a few bases, microRNAs often perform a critical function by switching the expression of certain genes off. Turning off gene expression is just as important a regulatory mechanism in plant development as switching genes on, Zhang noted.
Interfering with microRNA being loaded into a 'decoy' protein can cause various mutant phenotypes such as stunted growth in Arabidopsis plants. (Texas AgriLife Extension Service photo by Robert Burns)
This switching-off function of microRNA has been known for more than a decade. Further work had shown that it is microRNAs that actually guide the argonaute to actually do the switching off, sort of how a software application controls a smart phone or computer, according to Zhang.
Work by Zhang's team had demonstrated that if miR166/165 did not load into AGO10, or the AGO10 gene was missing, then the meristem part of the plant would be deformed, but why this was so remained a mystery.
Zhang and his team proposed that AGO10 functions as "a decoy for miR166/165″ to prevent it being loaded into other AGO proteins, particularly AGO1, which "plays a potent but inhibitory role in correct development of the meristem area cells," he said.
"In other words, if miR166/165 is loaded into AGO1, they would shut their target genes off," Zhang said. "But if miR166/165 is loaded into AGO10 protein, they won't switch-off target genes. Thus, AGO10 works in an opposite way compared to AGO1: It protects target genes and secures their expression."
|Contact: Robert Burns|
Texas A&M AgriLife Communications