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MicroRNAs play a crucial role in regulating plant growth, such as involving in the pathways of phytohormons signaling, which function in broad range of important aspects in many stages of plant development and evolution. To figure out the components part of microRNA in phytohormone signaling network, a sensitive photoelectrochemical biosensor was developed to detect miRNA-319a specifically using CuO-CuWO 4 as photoactive material and in situ generation electron donor technique. Taking the advantage of rolling circle amplification, nicking endonuclease triggered exponential amplification of target molecule, specific interaction between phosphate group and phos-tag and between biotin and avidin, the developed strategy can greatly amplify the detection signal only using trace amount of target miRNA-319a. The wide linear range was obtained from 1 fM to 0.1 nM and the detection limit was estimated to be 0.47 fM (S/N = 3). The developed method also showed good detection specificity. The effect of five phytohormones on the expression level of miRNA-319a in rice leaves was also investigated. This will be a basal principle of investigating the signaling network of phytohormones. [ABSTRACT FROM AUTHOR]

Herein, a sensitive and selective photoelectrochemical (PEC) immunoassay is developed for microRNA, where the graphite-like C 3 N 4 (g-C 3 N 4 ) is used as photoactive material and anti-DNA:RNA antibody is used as target microRNA recognition unit. With the doping of gold nanoparticles (AuNPs), the photoactivity of g-C 3 N 4 is greatly improved. The capture probe for microRNA is assembled on the AuNPs-g-C 3 N 4 modified ITO surface through the Au S bond. After hybridizing with target microRNA, the DNA:RNA hybrids can be recognized by anti-DNA:RNA antibody and this antibody can be further captured on the electrode surface. Through the specific interaction between antibody and alkaline phosphatase labeled IgG (ALP-IgG), ALP-IgG can be captured, which can catalyze the hydrolysis of ascorbic acid-2-phosphate (AAP) to produce ascorbic acid as electron donor. As a result, a strong photocurrent is obtained and the expression level of microRNA can be detected based the change of photocurrent. The fabricated biosensor presents good detection sensitivity with the linear range of 5–3000 fM and the detection limit of 2.26 fM. The developed biosensor also shows accepted detection selectivity with identifying even single-base mismatched microRNA. The applicability of the biosensor is further evaluated by assaying the expression level change of microRNA in rice leaves with and without phytohormone incubation. This work is not only providing a new detection platform for microRNA assay, but also affording some information on the role of microRNA in phytohormone signaling. [ABSTRACT FROM AUTHOR]