Yun Tian

Expression of TERF1 in rice regulates expression of stress-responsive genes and enhances tolerance to drought and high-salinity

Drought and high-salinity are the important constraints that severely affect plant development and crop yield worldwide. It has been established that ethylene response factor (ERF) proteins play important regulatory roles in plant response to abiotic and biotic stresses. Our previous researches have revealed that transgenic tobacco over-expressing TERF1 (encoding a tomato ERF protein) showed enhanced tolerance to abiotic stress. Here, we further investigate the function of TERF1 in transgenic rice. Compared with the wild-type plants, overexpression of TERF1 resulted in an increased tolerance to drought and high-salt in transgenic rice. And the enhanced tolerance may be associated with the accumulation of proline and the decrease of water loss. Furthermore, TERF1 can effectively regulate the expression of stress-related functional genes Lip5, Wcor413-l, OsPrx and OsABA2, as well as regulatory genes OsCDPK7, OsCDPK13 and OsCDPK19 under normal growth conditions. Our analyses of cis-acting elements show that there exist DRE/CRT and/or GCC-box existing in TERF1 targeted gene promoters. Our results revealed that ectopic expression of TERF1 in rice caused a series of molecular and physiological alterations and resulted in the transgenic rice with enhanced tolerance to abiotic stress, indicating that TERF1 might have similar regulatory roles in response to abiotic stress in tobacco and rice.

Overexpression of ethylene response factor TERF2 confers cold tolerance in rice seedlings

Rice (Oryza sativa L.) is a warm-season plant exposed to various stresses. Low temperature is an important factor limiting extension of rice cultivation areas and productivity. Previously, we have demonstrated that tomato ERF protein TERF2 enhances freezing tolerance of transgenic tobacco and tomato plants. Herein, we report that overexpression of TERF2 enhances transgenic rice tolerance to cold without affecting growth or agronomic traits. Physiological assays revealed that TERF2 could not only increase accumulation of osmotic substances and chlorophyll, but also reduce reactive oxygen species (ROS) and malondialdehyde (MDA) content and decrease electrolyte leakage in rice under cold stress. Further analysis of gene expression showed that TERF2 could activate expression of cold-related genes, including OsMyb, OsICE1, OsCDPK7, OsSODB, OsFer1, OsTrx23, and OsLti6, in transgenic rice plants under natural condition or cold stress. Thus, our findings demonstrated that TERF2 modulated expression of stress-related genes and a series of physiological adjustments under cold stress, indicating that TERF2 might have important regulatory roles in response to abiotic stress in rice and possess potential utility in improving crop cold tolerance.

Mechanisms of nisin resistance in Gram-positive bacteria

Nisin is the most prominent lantibiotic and is used as a food preservative due to its high potency against certain Gram-positive bacteria. However, the effectiveness of nisin is often affected by environmental factors such as pH, temperature, food composition, structure, as well as food microbiota. The development of nisin resistance has been seen among various Gram-positive bacteria. The mechanisms under the acquisition of nisin resistance are complicated and may differ among strains. This paper presents a brief review of possible mechanisms of the development of resistance to nisin among Gram-positive bacteria.

Proteomic analysis of cold stress responses in tobacco seedlings

Cold stress is one of the major abiotic stresses limiting the productivity and the geographical distribution of many important crops. To gain a better understanding of cold stress responses in tobacco ( Nicotiana tabacum ), we carried out a comparative proteomic analysis. Five-week-old tobacco seedlings were treated at 4°C for 4 h. Cold treatment resulted in stress phenotypes of smoothing and shallowing leaves and increased relative electrolyte leakage. The expression changes of total proteins in tobacco leaves were examined using two-dimensional electrophoresis. Quantitative image analysis revealed a total of 101 protein spots that changed their intensities significantly, 21 protein spots were down-regulated, eight were up-regulated after the cold treatment, 50 protein spots only expressed in the control sample, while 22 protein spots were only present in the cold treatment sample. Mass spectrometry analysis allowed the identification of 73 differentially expressed proteins, including well known and novel cold-responsive proteins. The identified proteins are involved in several processes such as photosynthesis, protein processing, redox homeostasis, ribonucleic acid (RNA) processing, signal transduction, translation, cell division/cycle, and metabolisms of carbon and energy. Several types of proteins showed enhanced degradation during chilling stress, especially the photosynthetic proteins. Gene expression analysis of 25 different proteins by reverse transcriptase- polymerase chain reaction (RT-PCR) showed that the messenger RNA (mRNA) levels of 18 genes correlated well with the protein levels. In conclusion, our study provides new insights into cold stress responses in tobacco and needs to be further studied in future. Key words : Proteomics, cold stress, tobacco (Nicotiana tabacum).

Genetic diversity evaluation of winged bean ( Psophocarpus tetragonolobus (L.) DC.) using inter-simple sequence repeat (ISSR)

AbstractWinged bean is an important vegetable with high nutritional value. Evaluating the genetic diversity is very helpful for scientific utilization for breeding and the germplasm resources for preservation. In this paper, we estimated the genetic distances of 45 accessions of winged bean using ISSR markers. The results demonstrated that winged bean germplasms had a little genetic variation with genetic dissimilarity coefficients ranging from 0.73 to 0.97. And the accessions could be divided into four groups. Our study is a few reports to evaluate the genetic diversity of different winged bean germplasms using the molecular marker, and the results provide a useful basis for germplasm research and breeding of winged bean.

Intersubunit physical couplings fostered by the left flipper domain facilitate channel opening of P2X4 receptors

P2X receptors are ATP-gated trimeric channels with important roles in diverse pathophysiological functions. A detailed understanding of the mechanism underlying the gating process of these receptors is thus fundamentally important and may open new therapeutic avenues. The left flipper (LF) domain of the P2X receptors is a flexible loop structure, and its coordinated motions together with the dorsal fin (DF) domain are crucial for the channel gating of the P2X receptors. However, the mechanism underlying the crucial role of the LF domain in the channel gating remains obscure. Here, we propose that the ATP-induced allosteric changes of the LF domain enable it to foster intersubunit physical couplings among the DF and two lower body domains, which are pivotal for the channel gating of P2X4 receptors. Metadynamics analysis indicated that these newly established intersubunit couplings correlate well with the ATP-bound open state of the receptors. Moreover, weakening or strengthening these physical interactions with engineered intersubunit metal bridges remarkably decreased or increased the open probability of the receptors, respectively. Further disulfide cross-linking and covalent modification confirmed that the intersubunit physical couplings among the DF and two lower body domains fostered by the LF domain at the open state act as an integrated structural element that is stringently required for the channel gating of P2X4 receptors. Our observations provide new mechanistic insights into P2X receptor activation and will stimulate development of new allosteric modulators of P2X receptors.

Exploration of the Peptide-recognition of an Amiloride-sensitive FMRFamide Peptide-gated Sodium Channel

FMRFamide (Phe-Met-Arg-Phe-NH2)-activated sodium channel (FaNaC) is an amiloride-sensitive sodium channel activated by endogenous tetrapeptide in invertebrates, and belongs to the epithelial sodium channel/degenerin (ENaC/DEG) superfamily. The ENaC/DEG superfamily differs markedly in its means of activation, such as spontaneously opening or gating by mechanical stimuli or tissue acidosis. Recently, it has been observed that a number of ENaC/DEG channels can be activated by small molecules or peptides, indicating that the ligand-gating may be an important feature of this superfamily. The peptide ligand control of the channel gating might be an ancient ligand-gating feature in this superfamily. Therefore, studying the peptide recognition of FaNaC channels would advance our understanding of the ligand-gating properties of this superfamily of ion channels. Here we demonstrate that Tyr-131, Asn-134, Asp-154, and Ile-160, located in the putative upper finger domain of Helix aspersa FaNaC (HaFaNaC) channels, are key residues for peptide recognition of this ion channel. Two HaFaNaC specific-insertion motifs among the ENaC/DEG superfamily, residing at the putative α4-α5 linker of the upper thumb domain and the α6-α7 linker of the upper knuckle domain, are also essential for the peptide recognition of HaFaNaC channels. Chemical modifications and double mutant cycle analysis further indicated that those two specific inserts and key residues in the upper finger domain together participate in peptide recognition of HaFaNaC channels. This ligand recognition site is distinct from that of acid-sensing ion channels (ASICs) by a longer distance between the recognition site and the channel gate, carrying useful information about the ligand gating and the evolution of the trimeric ENaC/DEG superfamily of ion channels.

The molecular mechanisms of male reproductive organogenesis in rice (Oryza sativa L.)

Stamen is the male reproductive organ of rice (Oryza sativa L.), and the development is a considerably significant stage during the sexual reproduction. It is very important to reveal what is the molecular mechanisms which controlling the development of stamen, and will be helpful in producing hybrid seeds by manipulating the male sterility. This article reviews the progress on the molecular mechanisms of male reproductive organogenesis in rice, which would facilitate the further studies on male sterile genes in rice.

The nonproton ligand of acid-sensing ion channel 3 activates mollusk-specific FaNaC channels via a mechanism independent of native FMRFamide peptide

The degenerin/epithelial sodium channel (DEG/ENaC) superfamily of ion channels contains subfamilies with diverse functions that are fundamental to many physiological and pathological processes, ranging from synaptic transmission to epileptogenesis. The absence in mammals of some DEG/ENaCs subfamily orthologues such as FMRFamide peptide–activated sodium channels (FaNaCs), which have been identified only in mollusks, indicates that the various subfamilies diverged early in evolution. We recently reported that the nonproton agonist 2-guanidine-4-methylquinazoline (GMQ) activates acid-sensing ion channels (ASICs), a DEG/ENaC subfamily mainly in mammals, in the absence of acidosis. Here, we show that GMQ also could directly activate the mollusk-specific FaNaCs. Differences in ion selectivity and unitary conductance and effects of substitutions at key residues revealed that GMQ and FMRFamide activate FaNaCs via distinct mechanisms. The presence of two activation mechanisms in the FaNaC subfamily diverging early in the evolution of DEG/ENaCs suggested that dual gating is an ancient feature in this superfamily. Notably, the GMQ-gating mode is still preserved in the mammalian ASIC subfamily, whereas FMRFamide-mediated channel gating was lost during evolution. This implied that GMQ activation may be essential for the functions of mammalian DEG/ENaCs. Our findings provide new insights into the evolution of DEG/ENaCs and may facilitate the discovery and characterization of their endogenous agonists.

Complete genome sequence of the Streptomyces sp. strain CdTB01, a bacterium tolerant to cadmium

Streptomyces sp. Strain CdTB01, which is tolerant to high concentrations of heavy metals, particularly cadmium, was isolated from soil contaminated with heavy metals. Two contigs with total genome size of 10.19Mb were identified in the whole genome sequencing and assembly, and numerous homologous genes known to be involved in heavy metal resistance were found in the genome.