Over-expression of a γ-tocopherol methyltransferase gene in vitamin E pathway confers PEG-simulated drought tolerance in alfalfa.

BACKGROUND: α-Tocopherol is one of the most important vitamin E components present in plant. α-Tocopherol is a potent antioxidant, which can deactivate photoproduced reactive oxygen species (ROS) and prevent lipids from oxidation when plants suffer drought stress. γ-Tocopherol methyltransferase (γ-TMT) catalyzes the formation of α-tocopherol in the tocopherol biosynthetic pathway. Our previous studies showed that over-expression of γ-TMT gene can increase the accumulation of α-tocopherol in alfalfa (Medicago sativa). However, whether these transgenic plants confer increased drought tolerance and the underlying mechanism are still unknown. RESULTS: In the present study, we further evaluate transgenic alfalfa lines, and found that over-expression of MsTMT led to an increase in α-tocopherol and total tocopherol level in the transgenic lines compared with the control plant. It was revealed that drought tolerance of the transgenic alfalfa was remarkably increased, with alleviated oxidative damage and accumulation of more osmolytic substances. The stomatal development in transgenic plants was significantly inhibited on both sides of leaves, which may be resulted from the repression of MsSPCHLESS (MsSPCH) gene. The reduced stomatal density of transgenic plants contributes to a lower stomatal conductance and higher water use efficiency (WUE). Moreover, both RNA-seq and qRT-PCR analyses indicate that regulatory mechanism of MsTMT in drought involved in both ABA-dependent and ABA-independent pathways. CONCLUSION: Our results suggest that MsTMT gene plays a positive role in regulating alfalfa response to PEG-simulated drought stress, which might involve complex mechanisms, including ROS scavenging system, stomatal development and multiple phytohormone signaling pathways. This study will broaden our view on the function of γ-TMT gene and provide new strategy for genetic engineering in alfalfa breeding.

Plasma pharmacokinetics of melamine and a blend of melamine and cyanuric acid in rainbow trout (Oncorhynchus mykiss).

The objective of the study was to obtain pharmacokinetic parameters for melamine and blend of melamine (MEL) and cyanuric acid (CYA) in rainbow trout (Oncorhynchus mykiss). The single target dosage of MEL (20mg/kg bw) and the blend of MEL and CYA (5 and 1.67 mg/kg bw, respectively) were designed and plasma samples were collected at 30 min, 1, 4, 8, 12, 20, 24, 36, 48, 72, 144 and 240 h sequentially. An optimized method for simultaneous determination of MEL and CYA in plasma and animal tissues by LC-MS/MS was used. The data were shown to best fit a non-compartment model with first order processes of linear characters for melamine, with half-life (t(½)) of 32.2-32.9h, clearance (Cl(z/F)) of 35.9-36.6 ml/h/kg, and volume of distribution (V(ss)) of 1.67-1.74 l/kg. Withdrawal of CYA was much more rapid than that of MEL with higher Cl(z/F) (783.56 ml/h/kg) and shorter t(½) (7.92 h). T(max) of MEL20 and MEL5 were 12 and 20 h, respectively, which showed that T(max) of MEL5 was delayed when MEL and CYA were given together. The results are quite different from those in mammals and showed much slower elimination of MEL and CYA from rainbow trout body.

Enhancement of surface plasmon resonance signals using a MIP/GNPs/rGO nano-hybrid film for the rapid detection of ractopamine.

A novel surface plasmon resonance (SPR) sensor that uses molecular imprinted polymers (MIPs) coated with gold nanoparticles (GNPs) and reduced graphene oxide (rGO) as a sensing nano-hybrid film was developed for detection of ractopamine. The MIPs were synthesized by precipitation polymerization and characterized by scanning electron microscopy and Scatchard analysis. The GNPs/rGO composite was synthesized by a single-step reduction of graphene oxide and HAuCl4 solution. The MIP/GNPs/rGO nano-hybrid film was immobilized onto a bare sensor chip and exhibited remarkable sensitivity and stability by the "grafting to" method with the assistance of ionic liquid (IL) as a binder. The prepared sensor showed class-specific selectivity for ractopamine (RAC) and its analogs under optimized conditions. The novel SPR sensor had a wide linear range over an RAC concentration from 20 to 1000 ng/mL with a detection limit of 5 ng/mL (S/N=3). The results demonstrated that the MIP/GNPs/rGO nano-hybrid film was suitable as the recognition element of the SPR sensorfor rapid screening and detection of beta-agonists such as RAC.