Expression of miRNAs involved in phosphate homeostasis and senescence is altered in glyphosate-treated maize

Abstract

Glyphosate is a systemic, nonselective and most widely used herbicide in the world. The introduction of glyphosate-resistant crops in the mid-1990s resulted in a dramatic increase in the use of glyphosate herbicide making it most widely used herbicide in the world. The average maize yield loss in the field caused by pests is around 20 % but in many regions it is much higher. It is now clear that glyphosate causes broader range of physiological alterations than previously assumed and some plants gain higher level of resistance to glyphosate without the need to use genetic engineering methods. To understand the mechanisms of such heightened resistance we must first know the processes mediating the plants’ death in response to glyphosate treatment. Here, we show that 12 miRNAs, belonging to miR167, miR396, miR159, miR156, miR169, miR444 and miR827 families, are significantly upregulated, and one, miR166, downregulated following glyphosate treatment. These miRNAs have been previously shown to be involved in abiotic stress responses and implicated in senescence. Strikingly, two of the induced miRNAs, miR444 and miR827, have been shown to regulate phosphate transport pathways, which seem to be common for Pi and glyphosate uptake.