The miR166d/TaCPK7-D Signaling Module Is a Critical Mediator of Wheat (Triticum aestivum L.) Tolerance to K+ Deficiency

Abstract

It is well established that potassium (K⁺) is an essential nutrient for wheat (<i>Triticum aestivum</i> L.) growth and development. Several microRNAs (miRNAs), including miR166, are reportedly vital roles related to plant growth and stress responses. In this study, a K⁺ starvation-responsive miRNA (miR166d) was identified, which showed increased expression in the roots of wheat seedlings exposed to low-K⁺ stress. The overexpression of miR166d considerably increased the tolerance of transgenic Arabidopsis plants to K⁺ deprivation treatment. Furthermore, disrupting miR166d expression via virus-induced gene silencing (VIGS) adversely affected wheat adaptation to low-K⁺ stress. Additionally, miR166d directly targeted the calcium-dependent protein kinase 7-D gene (<i>TaCPK7-D</i>) in wheat. The <i>TaCPK7-D</i> gene expression was decreased in wheat seedling roots following K⁺ starvation treatment. Silencing <i>TaCPK7-D</i> in wheat increased K⁺ uptake under K⁺ starvation. Moreover, we observed that the miR166d/<i>TaCPK7-D</i> module could affect wheat tolerance to K⁺ starvation stress by regulating <i>TaAKT1</i> and <i>TaHAK1</i> expression. Taken together, our results indicate that miR166d is vital for K⁺ uptake and K⁺ starvation tolerance of wheat via regulation of <i>TaCPK7-D</i>.