Effects of rainfall characteristics and sugarcane growth stage on soil and nitrogen losses.

High intensity rainfall in southern China has led to soil erosion on sloping farmland, causing serious ecological and environmental problems. But how the interaction of rainfall factors and growth stages influence soil erosion and nitrogen loss on sugarcane-cultivated slope under natural rainfall have not been studied considerably. This study concentrated on the in situ runoff plot observation test. Surface runoff, soil erosion, and nitrogen loss under individual natural rainfall events during the different sugarcane growth stages (seedling stage (SS), tillering stage (TS), elongation stage (ES)) from May to September in 2019 and 2020 were recorded and measured. The effects of rainfall factors (intensity and amount) on soil erosion and nitrogen loss were quantified by path analysis. The influence of rainfall factors and sugarcane planting on soil erosion and nitrogen loss was analyzed. Surface runoff, soil erosion, and nitrogen loss on sugarcane-cultivated slope were 4354.1 m3/ha, 155.4 t/ha, and 25.87 kg/ha during 2019 to 2020, and were mainly concentrated in SS, accounting for 67.2%, 86.9%, and 81.9% of total surface runoff, soil erosion, and nitrogen loss, respectively. Nitrogen losses were mainly concentrated in surface runoff, accounting for 76.1% of total nitrogen loss, and the main form in surface runoff was nitrate nitrogen (NO3--N, 92.9%). Under individual rainfall events, surface runoff, soil erosion, and nitrogen loss changed with the changing of rainfall characteristics and sugarcane growth. Surface runoff and nitrogen loss were obviously affected by rainfall characteristics, while the soil erosion and nitrogen loss were affected by both rainfall characteristics and sugarcane growth stages. Path analysis indicated that maximum rainfall intensities at 15 min (I15) and 60 min (I60) were most significant to the production of surface runoff and soil erosion with direct path coefficients of 1.19 and 1.23, respectively. NO3--N and ammonium nitrogen (NH4+-N) losses in surface runoff were mostly influenced by maximum rainfall intensity at 30 min (I30) and I15 with direct path coefficients of 0.89 and 3.08, respectively. NO3--N and NH4+-N losses in sediment yield were mostly influenced by I15 and rainfall amount, and the direct path coefficients were 1.61 and 3.39, respectively. The main stage of soil and nitrogen loss was seedling stage, while the significant factors of rainfall characteristics affecting surface runoff, soil erosion, and nitrogen loss were quite different. The results provide theoretical support for soil erosion and quantitative rainfall erosion factors of sugarcane-cultivated slope in southern China.

An electrochemical aptasensor based on target triggered multiple-channel DNAzymes cycling amplification strategy with PtFe@Co-MOF as signal amplifier.

A novel electrochemical aptasensor for the detection of Aflatoxin B1 (AFB1) was developed for the first time by using the target-triggered multiple-channel deoxyribozymes (DNAzymes) cycling amplified assay with Pt Fe doped NH2-Co-MOF (PtFe@Co-MOF) as a signal amplifier. In the presence of AFB1, a self-assembling cross-over nucleic structure could be triggered by AFB1 via two aptamers' structure switching for strand displacement, resulting in four channels of Mg2+-dependent DNAzyme recycling simultaneously to multiply the detection signals. These DNAzymes cyclically split the substrate sequence to release the PtFe@Co-MOF labeled detection probe (DP), which is subsequently hybridized with the capture probes on the Au-deposited glassy carbon electrode. The fabrication procedure was characterized by differential pulse voltammetry, and the results of the morphological and element composition characteristics methods were analyzed to determine the successful preparation of PtFe@Co-MOF. The limit of detection (LOD) for AFB1 detection was 2 pg mL-1 with a linear range from 5 pg mL-1 to 80 ng mL-1. By comparison, the enhanced detection sensitivity has been found to originate from the efficient shearing of DNAzymes, enhanced peroxidase-like capability, and multiple active sites of PtFe@Co-MOF. Besides, this aptasensor showed high specificity for AFB1 compared with similar mycotoxins and exhibited high accuracy with low experimental cost and easy operation. Furthermore, the unique design of electrochemical aptasensors could provide a promising platform for the onsite determination of AFB1, as well as other targets by replacing the aptamer and other core recognition sequences.

Binding of microRNA-135a (miR-135a) to homeobox protein A10 (HOXA10) mRNA in a high-progesterone environment modulates the embryonic implantation factors beta3-integrin (ITGß3) and empty spiracles homeobox-2 (EMX2).

BACKGROUND: Patients with elevated circulating progesterone concentrations on the day of the human chorionic gonadotropin (hCG) trigger had relatively low implantation rates during assisted reproductive treatments. In this study, we assess the hypothesis that different concentrations of progesterone regulate the expression of homeobox protein A10 (HOXA10) and its downstream genes through miRNA-135a. METHODS: MicroRNA-135a (miR-135a), HOXA10, beta3-integrin (ITGß3), and empty spiracles homeobox-2 (EMX2) expression levels in endometrial tissues from patients with elevated progesterone were measured. To determine the threshold of progesterone level which can impair implantation, Ishikawa cells were used to determine the expression of the aforementioned 4 genes after exposure to 5 graded concentrations of progesterone. The dual-luciferase reporter assay was used to verify whether miR-135a regulated the expression of HOXA10. Furthermore, the effects of HOXA10 on the expression of key endometrial receptivity genes ITGß3 and EMX2 were confirmed. RESULTS: High progesterone levels promoted miR-135a expression in vivo, and miR-135a bound to the 3'-untranslated region (3'-UTR) of HOXA10 mRNA to inhibit HOXA10 expression. Reduction of HOXA10 promoted EMX2 expression and inhibited ITG-3 production. Progesterone promoted the expression of HOXA10 in vitro at low concentrations. However, when the concentration was greater than 10-7 ng/mL, progesterone inhibited HOXA10 by promoting miR-135a expression, thereby altering the expression of related genes and affecting endometrial receptivity. CONCLUSIONS: In vitro, the trend in miR-135a expression (which first decreased and then increased) was in direct contrast to that of HOXA10 expression (which first increased and then decreased) as progesterone levels increased. The key factors regulating endometrial receptivity included ITGß3 and EMX2, which were confirmed to be regulated by HOXA10. High progesterone levels affected miR-135a expression, and miR-135a inhibited HOXA10 expression, thereby affecting endometrial receptivity.