Timely detection of Staphylococcus aureus (S. aureus) is critical because it can multiply to disease−causing levels in a matter of hours. Herein, a simple and sensitive DNA tetrahedral (Td) fluorescence signal amplifier with blue carbon quantum dots (bCDs) was prepared for sandwich detection of S. aureus. bCD was modified at the apex of Td, and an aptamer on Td was used to accurately identify and “adsorb” the amplifier to the surface of S. aureus. Atomic force microscopy (AFM) demonstrates the successful preparation of this signal amplifier. The fluorescence intensity emitted in this strategy increased 4.72 times. The strategy showed a stronger fluorescence intensity change, sensitivity (linear range of 7.22 × 100–1.44  × 109 CFU/mL with a LOD of 4 CFU/mL), and selectivity. The recovery rate in qualified pasteurized milk and drinking water samples was 96.54% to 104.72%. Compared with simple aptamer sandwich detection, these fluorescence signal amplifiers have improved fluorescence detection of S. aureus. Additionally, this fluorescent signal amplification strategy may be applied to the detection of other food pathogens or environmental microorganisms in the future.

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Background Wood (secondary xylem) of forests is widely used used in construction, paper making, furniture, and as a feedstock for biofuels. Wood development is strictly regulated by the phytohormone auxin and MicroRNAs (miRNAs). Currently, the regulatory mechanisms of auxin-induced miRNAs during wood formation in tree species remain unclear.Methods and results Here, we investigated the effect of auxin application on wood development in poplar and identified miRNAs in the stems treated with different concentrations (0 mg/L, CK; 5 mg/L, Low; 10 mg/L, High) of indol-3-butyric acid (IBA). High-throughput sequencing showed that the 24-nt sRNAs were the most abundant classes in three types of small RNA libraries. A total of 118 known miRNAs and 134 novel miRNAs were obtained. Sixty-nine unique developmental-related miRNAs exhibited specific expression patterns in response to auxin, which was consistent with the influence of auxin on wood development. 269 target genes of 69 auxin-responsive miRNAs were predicted. Of them, three novel miRNAs had the most number (≥9) of target genes, which correspondingly belong to SPL, GRF and ARF families. The evolutionary relationships and tissue expression patterns of these target genes were further analyzed. The relative expression levels of four representative miRNAs and their partial target genes were confirmed by using RT-qPCR.Conclusions The present study provides new insights into auxin-responsive miRNAs during wood development in trees.

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