Cesium Toxicity Alters MicroRNA Processing and AGO1 Expressions in Arabidopsis thaliana

Abstract

MicroRNAs (miRNAs) are short RNA fragments that play important roles in controlled gene silencing, thus regulating many biological processes in plants. Recent studies have indicated that plants modulate miRNAs to sustain their survival in response to a variety of environmental stimuli, such as biotic stresses, cold, drought, nutritional starvation, and toxic heavy metals. Cesium and radio-cesium contaminations have arisen as serious problems that both impede plant growth and enter the food chain through contaminated plants. Many studies have been performed to define plant responses against cesium intoxication. However, the complete profile of miRNAs in plants during cesium intoxication has not been established. Here we show the differential expression of the miRNAs that are mostly down-regulated during cesium intoxication. Furthermore, we found that cesium toxicity disrupts both the processing of pri-miRNAs and AGONOUTE 1 (AGO1)-mediated gene silencing. AGO 1 seems to be especially destabilized by cesium toxicity, possibly through a proteolytic regulatory pathway. Our study presents a comprehensive profile of cesium-responsive miRNAs, which is distinct from that of potassium, and suggests two possible mechanisms underlying the cesium toxicity on miRNA metabolism.

Dynamic roles of microRNAs in nutrient acquisition and plant adaptation under nutrient stress: A review

“…In case of Cu starvation, miR397, miR408, and miR857 were upregulated and thier targets were associated with laccase and plastocyanin gene families. Numerous other miRNAs were responsive to various other metal ions, such as Al, As, Hg, Cd and Cs toxicity, thereby altering the expression of plethora of stress related genes (Zeng et al, 2012;Zhou et al, 2012aZhou et al, , 2012bYang and Chen, 2013;Jung et al, 2015). The main idea of describing the dynamic regulatory roles of miRNAs during various nutrient stresses thereby targeting wide array of stress associated genes including transporters, was to establish the fact that miRNAs are critically involved at every step for maintaining the nutrient homeostasis; however, finding the upstream regulatory elements in this highly complex mechanism is still elusive.…”

ATP binding cassette proteins ABCG37 and ABCG33 function as potassium-independent cesium uptake carriers in Arabidopsis roots

“…Polyubiquitin-dependent endocytosis and degradation have been suggested to regulate this process (Martins et al, 2017). Cesium toxicity has already been reported to induce proteolytic degradation of AGO1 possibly through autophagy (Jung et al, 2015). The ferrous Fe uptake transporter IRON-REGULATED TRANSPORTER1 (IRT1) is shown to be rapidly and constitutively degraded through a ring E3 ubiquitin ligase IRT Degradation Factor 1 (IDF1)-mediated pathway to maintain cellular Fe homeostasis (Shin et al, 2013).…”

ATP Binding Cassette Proteins ABCG37 and ABCG33 are required for potassium-independent cesium uptake in Arabidopsis roots

“…Polyubiquitin-dependent endocytosis and degradation have been suggested to regulate this process (Martins et al, 2017). Cesium toxicity has already been reported to induce proteolytic degradation of AGO1 possibly through autophagy (Jung et al, 2015). The ferrous Fe uptake transporter IRON-REGULATED TRANSPORTER1 (IRT1) is shown to be rapidly and constitutively degraded through a ring E3 ubiquitin ligase IRT Degradation Factor 1 (IDF1)-mediated pathway to maintain cellular Fe homeostasis (Shin et al, 2013).…”