The potential role of plasma membrane proteins in response to Zn stress in rice roots based on iTRAQ and PRM under low Cd condition.

Cd pollution had already caused serious threats to crop growth and development, food safety and human health, and become a potential agricultural and global environmental problem. Zn had been used to reduce Cd accumulation in soil and plants. Proteins located in plasma membrane (PM) played important roles in transferring stress signals in plants. To further elucidate how PM proteins modulated Zn/Cd transport under low-Cd condition, quantitative proteomics was employed to identify and verify the differentially expressed proteins (DEPs) and their biological functions at proteome level. A total of 4008 proteins were identified, and 332 DEPs (192 up and 140 down, fold >1.50 or <0.66, p < 0.01) were screened. Functional analysis showed that DEPs were mainly catalytic active and binding proteins, involved in glutathione metabolism, phenylpropanoid biosynthesis, etc. DEPs involved in ion transport played key roles in regulating transmembrane transport, resisting stress and alleviating toxicity of heavy metals to rice roots. DEPs were as the marker proteins in rice root responding to heavy metal stress. This study had important guiding significances for metal ions transport mechanism and screening of biomarkers responding to abiotic stress, and provided references for further researches underlying abiotic stress and detoxication in rice and other plants.

[Simultaneous determination of six novel acetolactate synthase inhibitor herbicide residues in oil crops based on ultrasound assisted extraction liquid chromatography-tandem mass spectrometry].

Ultrasound-assisted extraction coupled with liquid chromatography-tandem mass spectrometry (UAE-LC-MS/MS) was used to develop a trace multi-residue detection method for six novel acetolactate synthase (ALS) inhibitor herbicide residues (mesosulfuron-methyl, halosulfuron-methyl, bispyribac-sodium, pyriminobac-methyl, orthosulfamuron, and ethoxysulfuron) in oil crops. In this study, the recoveries of the six herbicides based on ultrasound-assisted and QuEChERS extraction methods were compared, and five adsorbent materials (C18, PSA, GCB, Florisil, and EMR) were optimized based on their purification and adsorption capacities. The results showed that the ultrasound-assisted extractions gave recoveries greater than 90% for the six compounds. Furthermore, EMR showed little adsorption for the six compounds and a reduced matrix effect by effective removal of the oil lipids. The six herbicide residues had good linearities in the concentrations ranging from 0.05 to 500.0 µg/L, and the correlation coefficients were greater than 0.9984. The limits of detection and limits of quantification for this method were 0.08-0.8 µg/kg and 0.25-2.5 µg/kg, respectively. The recoveries of the six pesticides at three spiked levels in four matrices (rapeseed, soybean, peanut, and sunflower seed) ranged from 70.7% to 103.8%, with relative standard deviations of 0.8%-9.2%. This method was successfully applied to the simultaneous determination of six ALS inhibitor herbicide residues in oil crops.

[Two-dimensional liquid chromatography separation and high resolution mass spectrometry analysis for proteome of rice leaves based on different extraction methods].

A two-dimensional liquid chromatography (2D LC) system was developed to separate proteins from rice leaves, which was extracted by phenol method, followed by the analysis with linear trap quadrupole orbitrap mass spectrometry (LTQ/Orbitrap MS). After proteins were extracted with phenol method, the enzymolytic peptides were separated by offline two-dimensional RP-RP system and detected by LTQ/Orbitrap MS, yielding 2712 proteins. Liquid chromatography separation system (1D LC and 2D LC) and protein extraction methods (phenol method, sodium dodecyl sulfate method (SDS method) and trichloroacetic acid/acetone method (TCA/acetone method)) were compared. Proteins identified by 2D LC were 2712, 2415 and 1914 with the above three extraction methods, respectively. The proteins were 2.7-fold, 2.5-fold and 1.9-fold the number of proteins identified by 1D LC respectively. And in terms of 2D LC, the proteins identified by phenol method were 297 and 798 more than SDS method and TCA/acetone method, respectively. Some proteins with extreme properties, such as very acidic or basic protein and high relative molecular mass proteins, were only identified in phenol method. Furthermore, proteins, which were extracted by different extraction methods and separated by 2D LC, were classified according to biological functions. It was found that protein functions by the three extraction methods were complementary. However, phenol method had the most variety of functions. The method provides technological support for rice proteomics and reference for research techniques of other crop proteomics.

Correction to: Analysis of bronopol (2-bromo-2-nitropropan-1,3-diol) residues in rice (Oryza sativa L.) by SPE using Bond Elut Plexa and liquid chromatography-tandem mass spectrometry.

The authors would like to call the reader's attention to the fact that unfortunately during a recent cross-check of the experimental record, they found that the positions of intercept and slope were reversed in Table 1 in the original manuscript. The authors apologize for the mistake.

Analysis of four sulfonylurea herbicides in cereals using modified Quick, Easy, Cheap, Effective, Rugged, and Safe sample preparation method coupled with liquid chromatography-tandem mass spectrometry.

A modified Quick, Easy, Cheap, Effective, Rugged, and Safe (QuEChERS) sample preparation method, coupled with liquid chromatography-electrospray ionization tandem mass spectrometry, has been developed for the simultaneous analysis of four commonly used sulfonylurea herbicides, ethoxysulfuron, halosulfuron-methyl, mesosulfuron-methyl and orthosulfamuron, in rice, maize, wheat and soybean. Adsorption of the analytes onto the primary-secondary amine used in the clean-up step was avoided by using 1% formic acid in acetonitrile as the extraction solvent to maintain the acidic herbicides in a non-ionized state. Trueness studies were carried out at three levels (2.5, 25 and 250 µg/kg for ethoxysulfuron and 5, 50 and 500 µg/kg for the other three analytes). Promising trueness (70.2%-119.8%) was achieved for all herbicides in all matrices after clean-up, with relative standard deviations (RSDr) < 18.6%. Satisfactory matrix effects (-19.7% to 14.8%) were also obtained. Good linearity of the calibration curves was achieved, with determination coefficients (r) ≥ 0.9956, when the concentration of ethoxysulfuron was in the range 0.5-50 µg/L and that of the other three analytes was in the range 1.0-500 µg/L. The RSDwR for within-laboratory reproducibility was 5.7%. The validated method was successfully used to analyze real samples.

Analysis of bronopol (2-bromo-2-nitropropan-1, 3-diol) residues in rice (Oryza sativa L.) by SPE using Bond Elut Plexa and liquid chromatography-tandem mass spectrometry.

A novel method has been developed for the direct, sensitive, and rapid detection of bronopol in rice using a simple solid-phase extraction (SPE) procedure followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), with electrospray ionization (ESI). Bronopol was stable under acidic conditions, and an acidic environment was thus needed before sample loading to ensure the stability of bronopol. Rice extracts containing bronopol were pretreated using a hydrophilic-lipophilic balanced (Bond Elut Plexa) cartridge to reduce the matrix effect. An XDB-C18 column (150 mm × 2.1 mm, 3.5 µm) was used for chromatographic separations, with a mobile phase comprising methanol and aqueous ammonium formate (5 mM). The linearity of the method was satisfactory with regression coefficient (R 2) = 0.9992. The limit of quantification was 3.3 µg kg-1. Three spiked levels (25, 125 and 625 µg kg-1) were used to determine the recovery of bronopol, which was found to be 73.3-96.7%, with relative standard deviations (RSD) in the range 1.2-7.9%. The RSD for intra-day precision (n = 7) was 7.6% and the RSD for inter-day precision (n = 15) was 8.3%. The newly developed analytical method was successfully used to quantify bronopol in rice samples.

[Determination of pyriminobac-methyl and bispyribac-sodium residues in rice by liquid chromatography-tandem mass spectrometry based on QuEChERS].

A method was developed for the determination of pyriminobac-methyl and bispyribac-sodium residues in rice by liquid chromatography-tandem mass spectrometry (LC-MS/MS) coupled with modified QuEChERS. The samples were extracted with acidified acetonitrile, and then purified by octadecylsilane bonded silica (C18) adsorbents. The analytes were separated on a ZORBAX SB C18 column through a gradient elution using 0.1% (v/v) aqueous formic acid aqueous containing 5 mmol/L ammonium acetate and acetonitrile as mobile phases. Positive electrospray ionization (ESI+) was used. Qualitative work was performed using selected dynamic multiple reaction monitoring (dynamic MRM) mode. Quantization was performed using external standard method. The results showed good linearities of pyriminobac-methyl and bispyribac-sodium with correlation coefficients (r2) not less than 0.996. The limits of detection (LODs) of the method were 0.8 µ g/kg for pyriminobac-methyl, and 3 µ g/kg for bispyribac-sodium. The mean spiked recoveries of pyriminobac-methyl and bispyribac-sodium at three spiked levels were 76.6%-85.6% and 73.0%-86.7%, respectively, and the relative standard deviations (RSDs) of pyriminobac-methyl and bispyribac-sodium were 0.9%-3.4% and 1.2%-5.5%, respectively. This method is simple, rapid, sensitive, and suitable for the simultaneous determination of pyriminobac-methyl and bispyribac-sodium in rice.