Characterization of a transcription factor SlNAC7 gene from Suaeda liaotungensis and its role in stress tolerance.

NAC (NAM, ATAF1/2, CUC2) transcription factors play important roles in plant growth, development, and responses to abiotic stress. In this study, we cloned an NAC2 subfamily transcription factor gene (SlNAC7) from the halophyte Suaeda liaotungensis K., and conducted a series of studies to determine the characteristics and functions of this gene. The SlNAC7 coding region contains 1719 base pairs that encode a 573 amino acid long protein. SlNAC7 is expressed in the roots, stems, and leaves of S. liaotungensis, with the highest expression in the leaves. We found that SlNAC7 expression can be induced by drought, salt, cold, and abscisic acid. Transient expression in onion epidermal cells revealed that SlNAC7 is located in both the nucleus and cytoplasm. A transcriptional activation experiment in yeast showed that the transcriptional activation domain of SlNAC7 is located at the C terminus. When SlNAC7 was transformed into Arabidopsis under the control of a CaMV 35S promoter its overexpression was found to enhance the ability of transgenic plants to resist drought, salt, and cold stress. Moreover, these plants showed multiple changes in growth characteristics and physiological and biochemical indices in response to different stresses, as well as the upregulation of numerous stress-related genes. We have thus characterized a new halophyte-derived NAC transcription factor, SlNAC7, which can regulate plant growth and physiological and biochemical changes under adverse conditions by regulating the expression of stress-related genes, thereby enhancing plant stress resistance. SlNAC7 is a promising candidate for breeding new varieties of stress-tolerant crops.

Sex-biased gene expression in dioecious garden asparagus (Asparagus officinalis).

Sex chromosomes have evolved independently in phylogenetically diverse flowering plant lineages. The genes governing sex determination in dioecious species remain unknown, but theory predicts that the linkage of genes influencing male and female function will spur the origin and early evolution of sex chromosomes. For example, in an XY system, the origin of an active Y may be spurred by the linkage of female suppressing and male promoting genes. Garden asparagus (Asparagus officinalis) serves as a model for plant sex chromosome evolution, given that it has recently evolved an XX/XY sex chromosome system. In order to elucidate the molecular basis of gender differences and sex determination, we used RNA-sequencing (RNA-Seq) to identify differentially expressed genes between female (XX), male (XY) and supermale (YY) individuals. We identified 570 differentially expressed genes, and showed that significantly more genes exhibited male-biased than female-biased expression in garden asparagus. In the context of anther development, we identified genes involved in pollen microspore and tapetum development that were specifically expressed in males and supermales. Comparative analysis of genes in the Arabidopsis thaliana, Zea mays and Oryza sativa anther development pathways shows that anther sterility in females probably occurs through interruption of tapetum development before microspore meiosis.

Genomic data and ecological niche modeling reveal an unusually slow rate of molecular evolution in the Cretaceous Eupteleaceae.

Living fossils are evidence of long-term sustained ecological success. However, whether living fossils have little molecular changes remains poorly known, particularly in plants. Here, we have introduced a novel method that integrates phylogenomic, comparative genomic, and ecological niche modeling analyses to investigate the rate of molecular evolution of Eupteleaceae, a Cretaceous relict angiosperm family endemic to East Asia. We assembled a high-quality chromosome-level nuclear genome, and the chloroplast and mitochondrial genomes of a member of Eupteleaceae (Euptelea pleiosperma). Our results show that Eupteleaceae is most basal in Ranunculales, the earliest-diverging order in eudicots, and shares an ancient whole-genome duplication event with the other Ranunculales. We document that Eupteleaceae has the slowest rate of molecular changes in the observed angiosperms. The unusually low rate of molecular evolution of Eupteleaceae across all three independent inherited genomes and genes within each of the three genomes is in association with its conserved genome architecture, ancestral woody habit, and conserved niche requirements. Our findings reveal the evolution and adaptation of living fossil plants through large-scale environmental change and also provide new insights into early eudicot diversification.

Covalent organic framework linked with amination luminol derivative as enhanced ECL luminophore for ultrasensitive analysis of cytochrome c.

Cytochrome c (cyt c) plays a critical role in mitochondrial respiratory chain, whose absence is detrimental to electron transport and reduce adenosine triphosphate. For ultrasensitive detection of cyt c, sheet-like covalent organic frameworks (COFs) were prepared by orderly accumulation of 1,3,5-benzenetricarboxaldehyde (BTA) and p-phenylenediamine (PDA), and further grafted with N-(4-aminobutyl)-N-ethylisoluminol (ABEI) - an electrochemiluminescence (ECL) emitter. Specifically, the morphology and structure of the COFs-ABEI were mainly characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis, and X-ray photoelectron spectroscopy (XPS). In parallel, the optical properties of the emitter were certified by UV-vis absorbance spectroscopy, Fourier infrared spectroscopy (FTIR), fluorescence (FL), and ECL measurements, showing 2.25-time enhanced ECL efficiency over pure ABEI, coupled by illustrating the interfacial electron transport mechanism. On the above foundation, a label-free "signal off" ECL biosensor was constructed by virtue of the specific immune recognition between the aptamer of the target cyt c with its capture DNA (cDNA) anchored on the biosensing platform, exhibiting a wider linear range of 1.00 fg mL-1-0.10 ng mL-1 (R2 = 0.998) and a lower limit of detection (LOD) down to 0.73 fg mL-1. This work offers some constructive guidelines for sensitive bioassays of disease-related biomarkers in the clinical field.

Residue analysis of tetracyclines in milk by HPLC coupled with hollow fiber membranes-based dynamic liquid-liquid micro-extraction.

A novel hollow fiber membranes-based dynamic liquid-liquid micro-extraction (HF-DLLME) coupled with HPLC-UV detection has been developed for the residue analysis of tetracyclines in milk samples without deproteinization and degreasing. The influences of experimental parameters were investigated and optimized. The method showed a good performance. The limits of detection (LOD) are in the range of 0.95-3.6µg/L. The recoveries in spiked samples range from 92.38 to 107.3%. The relative standard deviations (RSDs) are lower than 8.66%. The advantages of this method are simple operation, high efficiency, absence of sample carryover and low cost.

Cholesterol, not polyunsaturated fatty acids, is target molecule in oxidation induced by reactive oxygen species in membrane of human erythrocytes.

The oxidation of polyunsaturated fatty acids (PUFAs) by reactive oxygen species (ROS) is linked to aging and to many diseases. We herein employ initiating peroxyl radical (ROO(.-)) derived from the decomposition of 2,2\'- azobis(2-amidinopropane dihydrochloride), hydroxyl radical generated by the Fenton reaction and peroxyl radical (ROO(.-)) and alkoxyl radical (LO(.-)) derived from PUFAs by addition of Cu(2+) as ROS sources to oxidize human erythrocytes in vitro. The fatty acids in the erythrocyte membrane are transesterified from phosphoglycerides under alkaline conditions in the presence of methanol instead of being treated traditionally by diazomethane (CH(2)N(2)) under acidic conditions (pH = 2.0), to obtain corresponding methyl esters for the combination of gas chromatography with mass spectrometry determination. It was found that all the PUFAs in the membrane are perfectly preserved after oxidation by ROS, even though sufficient time is available for the interaction between human erythrocytes and ROS. This indicates that ROS do not damage PUFAs during reaction time. However, three products (cholesta-4,6-dien-3-ol, cholesta-4,6-dien-3-one, and cholesta-3,5-dien-7-one) are produced from the oxidation of cholesterol within this time frame. This qualitative finding suggests that the cholesterol in the membrane of human erythrocytes is more susceptible to ROS-induced oxidation than are PUFAs, and compels us to re-evaluate the physiological roles of cholesterol and PUFAs in the human erythrocyte membrane.