Integrative transcriptomic and TMT-based proteomic analysis reveals the mechanism by which AtENO2 affects seed germination under salt stress.

Seed germination is critical for plant survival and agricultural production and is affected by many cues, including internal factors and external environmental conditions. As a key enzyme in glycolysis, enolase 2 (ENO2) also plays a vital role in plant growth and abiotic stress responses. In our research, we found that the seed germination rate was lower in the AtENO2 mutation (eno2- ) than in the wild type (WT) under salt stress in Arabidopsis thaliana, while there was no significant difference under normal conditions. However, the mechanisms by which AtENO2 regulates seed germination under salt stress remain limited. In the current study, transcriptome and proteome analyses were used to compare eno2- and the WT under normal and salt stress conditions at the germination stage. There were 417 and 4442 differentially expressed genes (DEGs) identified by transcriptome, and 302 and 1929 differentially expressed proteins (DEPs) qualified by proteome under normal and salt stress conditions, respectively. The combined analysis found abundant DEGs and DEPs related to stresses and hydrogen peroxide removal were highly down-regulated in eno2- . In addition, several DEGs and DEPs encoding phytohormone transduction pathways were identified, and the DEGs and DEPs related to ABA signaling were relatively greatly up-regulated in eno2- . Moreover, we constructed an interactive network and further identified GAPA1 and GAPB that could interact with AtENO2, which may explain the function of AtENO2 under salt stress during seed germination. Together, our results reveal that under salt stress, AtENO2 mainly affects the expression of genes and proteins related to the phytohormone signal transduction pathways, stress response factors, and reactive oxygen species (ROS), and then affects seed germination. Our study lays the foundation for further exploration of the molecular function of AtENO2 under salt stress at the seed germination stage in Arabidopsis thaliana.

Enolase2 regulates seed fatty acid accumulation via mediating carbon partitioning in Arabidopsis thaliana.

In many higher plants, fatty acid (FA) biosynthesis is coordinately regulated at multiple levels by intricate regulatory networks. However, the factors and their regulatory mechanisms underlying seed oil accumulation are still limited. Here, we identified that loss of glycolytic metalloenzyme enolase2 (AtENO2) activity increased the contents of total FAs and salicylic acid (SA) but reduced the accumulation of flavonoids and mucilage by regulating the expression of key genes involved in their biosynthesis pathway in Arabidopsis thaliana seeds. AtENO2 physically interacts with the transcription factor AtTGA5, which may participate in the regulation of SA levels. Non-targeted metabolomics analysis of eno2- and WT also showed that the levels of three flavonoids, quercetin-3-galactoside, quercitrin, and epicatechin, were significantly decreased in eno2- , and the flavonoid biosynthesis pathway was also enriched in the KEGG analysis. Meanwhile, the mutation of AtENO2 delayed silique ripening, thereby prolonging silique photosynthesis time, allowing siliques to generate more photosynthesis products for FA biosynthesis. These results reveal a molecular mechanism by AtENO2 to regulate seed oil accumulation in A. thaliana, providing potential targets for improving crop seed oil quality.

Questionnaire development on measuring parents' anxiety about their children's education: Empirical evidence of parental perceived anxiety data for primary and secondary school students in China.

Background: With the implementation of the "double reduction" policy in China, parents of primary and secondary school students are experiencing a growing trend of educational anxiety that needs to be alleviated. Objective: To manage the education anxiety risk of parents of primary and secondary school students, a measurement questionnaire of parents' anxiety about their children's education (MQPAE) was developed and its reliability and validity were evaluated. Methods: A self-administered MQPAE was developed. An online crowdsourcing questionnaire platform was used to collect data on parents' anxiety about their children's education (PAE), and parents of primary and secondary school students in Hefei, China, were selected as the study population. The randomly extracted 5,747 questionnaires were gradually screened by discrete trend method, t-test, and Pearson's correlation coefficient method for the initial screening of PAE items, based on which exploratory factor analysis (EFA) was conducted for the final screening of questionnaire items and the reliability of the questionnaire. The reliability of the questionnaire was assessed by internal consistency and Pearson's correlation coefficient analysis. Confirmatory factor analysis (CFA) was conducted using 639 pre-selected data to investigate the validity of the questionnaire. Structural equation modeling was used to investigate the structural validity of the questionnaire, and average variance extracted (AVE), combined reliability (CR), and maximum of shared squared variance (MSV) were used to test for convergent and discriminant validity. Results: Exploratory factor analysis extracted five factors with a cumulative variance contribution of 65.66%. The CFA showed that χ2/df = 4.306, CFI = 0.920, NFI = 0.898, RMSEA = 0.072<0.08, AGFI = 0.839>0.80, PNFI = 0.793 and PGFI = 0.708. The overall Cronbach's α coefficient of the questionnaire was 0.956, and the factors' Cronbach's α coefficients were 0.926, 0.857, 0.913, 0.901, and 0.768, respectively. Repeated measurements of Pearson's correlation coefficients were 0.908, 0.911, 0.873, 0.891, 0.907 and 0.885 (all p < 0.001). The AVE was greater than 0.5 and the CR was greater than 0.7, and the value of the MSV was less than the corresponding AVE. Conclusion: The MQPAE has good reliability and validity and can be used in studies related to PAE of primary and secondary school students.

Regulatory Mechanisms of Anthocyanin Biosynthesis in Apple and Pear.

Anthocyanins contribute to the quality and flavour of fruits. They are produced through the phenylpropanoid pathway, which is regulated by specific key genes that have been identified in many species. The dominant anthocyanin forms are reversibly transformed at different pH states, thus forming different colours in aqueous solutions. In plants, anthocyanins are controlled by specific factors of the biosynthetic pathway: light, temperature, phytohormones and transcription factors. Although great progress in research on anthocyanin structures and the regulation of anthocyanin biosynthesis has been made, the molecular regulatory mechanisms of anthocyanin biosynthesis in different plants remain less clear. In addition, the co-regulation of anthocyanin biosynthesis is poorly understood. In this review, we summarise previous findings on anthocyanin biosynthesis, including the biochemical and biological features of anthocyanins; differences in anthocyanin biosynthesis among fruit species, i.e., apple, red pear, and the model plant Arabidopsis thaliana; and the developmental and environmental regulation of anthocyanin accumulation. This review reveals the molecular mechanisms underlying anthocyanin biosynthesis in different plant species and provides valuable information for the development of anthocyanin-rich red-skinned and red-fleshed apple and pear varieties.

Deep Sequencing of Small RNA Reveals the Molecular Regulatory Network of AtENO2 Regulating Seed Germination.

Seed germination is a key step in the new life cycle of plants. In agriculture, we regard the rapid and consistent process of seed germination as one of the necessary conditions to measure the high quality and yield of crops. ENO2 is a key enzyme in glycolysis, which also plays an important role in plant growth and abiotic stress responses. In our study, we found that the time of seed germination in AtENO2 mutation (eno2-) was earlier than that of wild type (WT) in Arabidopsis thaliana. Previous studies have shown that microRNAs (miRNAs) were vital in seed germination. After deep sequencing of small RNA, we found 590 differentially expressed miRNAs in total, of which 87 were significantly differentially expressed miRNAs. By predicting the target genes of miRNAs and analyzing the GO annotation, we have counted 18 genes related to seed germination, including ARF family, TIR1, INVC, RR19, TUDOR2, GA3OX2, PXMT1, and TGA1. MiR9736-z, miR5059-z, ath-miR167a-5p, ath-miR167b, ath-miR5665, ath-miR866-3p, miR10186-z, miR8165-z, ath-miR857, ath-miR399b, ath-miR399c-3p, miR399-y, miR163-z, ath-miR393a-5p, and ath-miR393b-5p are the key miRNAs regulating seed germination-related genes. Through KEGG enrichment analysis, we found that phytohormone signal transduction pathways were significantly enriched, and these miRNAs mentioned above also participate in the regulation of the genes in plant hormone signal transduction pathways, thus affecting the synthesis of plant hormones and further affecting the process of seed germination. This study laid the foundation for further exploration of the AtENO2 regulation for seed germination.

AtENO2 functions in the development of male gametophytes in Arabidopsis thaliana.

Pollen fertility is an important factor affecting the seed setting rate and seed yield of plants. The Arabidopsis thaliana enolase gene ENO2 (AtENO2) can affect the pollen morphology, germination, and pollen tube growth. AtENO2 encodes two proteins AtENO2 and AtMBP-1. To examine the effect of AtENO2 protein on pollen development, the 2nd ATG of the AtENO2 coding sequence for AtMBP-1 was mutated by site-directed mutagenesis, and transgenic plants expressing only AtENO2 but not AtMBP-1 were obtained. Phenotypic analysis indicated that AtENO2 was essential in the pollen development. The mechanisms of AtENO2 on pollen development were analyzed. AtENO2 can affect development of the pollen intine, and the mechanism may be that AtENO2 regulated the methyl esterification of pectin in pollen intine through ARF3 and AtPMEI-pi. The -734 ∼ -573 sequence of AtENO2 promoter is the main transcriptional regulatory region of AtENO2 affecting pollen development. The functional cis-acting element may be GTGANTG10(GTGA), and the trans-acting factors may be KAN, AS2 and ARF3/ETT. Moreover, the deletion of AtENO2 can cause significant difference in the expression of multiple genes related to pollen exine development. These results are useful for further studying the function of AtENO2 and exploring the mechanism of plant pollen development.

Formation pattern and regulatory mechanisms of pollen wall in Arabidopsis.

In angiosperms, mature pollen is wrapped by a pollen wall, which is important for maintaining pollen structure and function. Pollen walls provide protection from various environmental stresses and preserve pollen germination and pollen tube growth. The pollen wall structure has been described since pollen ultrastructure investigations began in the 1960s. Pollen walls, which are the most intricate cell walls in plants, are composed of two layers: the exine layer and intine layer. Pollen wall formation is a complex process that occurs via a series of biological events that involve a large number of genes. In recent years, many reports have described the molecular mechanisms of pollen exine development. The formation process includes the development of the callose wall, the wavy morphology of primexine, the biosynthesis and transport of sporopollenin in the tapetum, and the deposition of the pollen coat. The formation mechanism of the intine layer is different from that of the exine layer. However, few studies have focused on the regulatory mechanisms of intine development. The primary component of the intine layer is pectin, which plays an essential role in the polar growth of pollen tubes. Demethylesterified pectin is mainly distributed in the shank region of the pollen tube, which can maintain the hardness of the pollen tube wall. Methylesterified pectin is mainly located in the top region, which is beneficial for improving the plasticity of the pollen tube top. In this review, we summarize the developmental process of the anther, pollen and pollen wall in Arabidopsis; furthermore, we describe the research progress on the pollen wall formation pattern and its molecular mechanisms in detail.

The pip1s Quintuple Mutants Demonstrate the Essential Roles of PIP1s in the Plant Growth and Development of Arabidopsis.

Plasma membrane intrinsic proteins (PIPs) transport water, CO2 and small neutral solutes across the plasma membranes. In this study, we used the clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated protein 9 system (CRISPR/Cas9) to mutate PIP1;4 and PIP1;5 in a pip1;1,2,3 triple mutant to generate a pip1;1,2,3,4,5 (pip1s-) quintuple mutant. Compared to the wild-type (WT) plant, the pip1s- mutants had smaller sized rosette leaves and flowers, less rosette leaf number, more undeveloped siliques, shorter silique and less seeds. The pollen germination rate of the pip1s- mutant was significantly lower than that of the WT and the outer wall of the pip1s- mutant's pollen was deformed. The transcriptomic analysis showed significant alterations in the expression of many key genes and transcription factors (TFs) in the pip1s- mutant which involved in the development of leaf, flower and pollen, suggesting that the mutant of PIP1s not only directly affects hydraulics and carbon fixation, but also regulates the expression of related genes to affect plant growth and development.

Transcriptome analysis reveals the mechanism of anthocyanidins biosynthesis during grains development in purple corn (Zea mays L.).

Anthocyanidins are important pigments that cause plant tissues to develop colors. They have attracted much attention due to their crucial regulatory roles in plant growth as well as their health benefits. In order to reveal the molecular mechanism of anthocyanidin synthesis and regulation in purple corn (Zea mays L.) in this study, purple corn 963 was used to compare differences in gene expression during three stages of grain development by transcriptome analysis. A total of 17,168 differentially expressed genes (DEGs) (7564 up-regulated and 9604 down-regulated DGEs) were identified. The DEGs were significantly enriched in "Phenylpropanoid biosynthesis", "Biosynthesis of secondary metabolites", and "Plant hormone signal transduction". In addition, 72 % of the structural genes that regulate anthocyanidin synthesis were up-regulated, and the transcription factors related to the accumulation of anthocyanidins were enriched during grain development. Moreover, the differential expression of phytohormone genes might also be an important factor in anthocyanidin accumulation. Transcriptomic analysis presents a molecular basis for the study of grain color changes in the three stages of grain development, and provides information for further research on the mechanism of anthocyanidin synthesis.

ENO2 Affects the Seed Size and Weight by Adjusting Cytokinin Content and Forming ENO2-bZIP75 Complex in Arabidopsis thaliana.

Arabidopsis thaliana ENO2 (AtENO2) encodes two proteins AtENO2 (enolase) and AtMBP-1 (c-Myc binding protein 1-like). The loss of AtENO2 function causes the constitutive developmental defects which are correlated with reduced enolase activity, but not AtMBP-1 transcript abundance. However, the regulation mechanism of AtENO2 on the seed properties is still not clear. In this study, we found that the mutation of AtENO2 reduced the seed size and weight. The level of glucose in seed was significantly elevated but that of starch was decreased in AtENO2 mutants compared to WT plants. We also found that AtENO2 mutation reduced the content of cytokinin which resulted in smaller cotyledons. The RNA-seq data showed that there were 1892 differentially expressed genes and secondary metabolic pathways were significantly enriched. Instead of AtMBP-1, AtENO2 protein interacted with AtbZIP75 which may mediate the secondary metabolism. Therefore, ENO2 alters the size and weight of seeds which is not only regulated by the content of cytokinin and secondary metabolism, but may be affected by the interaction of ENO2 and bZIP57. These results are helpful to understand the novel function of AtENO2 which provide a foundation for further exploration of the key candidate genes for crop breeding.

Biological functions of Arabidopsis thaliana MBP-1-like protein encoded by ENO2 in the response to drought and salt stresses.

Arabidopsis thaliana ENO2 (AtENO2) plays an important role in plant growth and development. It encodes two proteins, a full-length AtENO2 and a truncated version, AtMBP-1, alternatively translated from the second start codon of the mRNA. The AtENO2 mutant (eno2- ) exhibited reduced leaf size, shortened siliques, a dwarf phenotype and higher sensitivity to abiotic stress. The objectives of this study were to analyze the regulatory network of the ENO2 gene in plant growth development and understand the function of AtENO2/AtMBP-1 to abiotic stresses. An eno2- /35S:AtENO2-GFP line and an eno2- /35S:AtMBP-1-GFP line of Arabidopsis were obtained. Results of sequencing by 454 GS FLX identified 578 upregulated and 720 downregulated differential expressed genes (DEGs) in a pairwise comparison (WT-VS-eno2- ). All the high-quality reads were annotated using the Gene Ontology (GO) terms. The DEGs with KEGG pathway annotations occurred in 110 pathways. The metabolic pathways and biosynthesis of secondary metabolites contained more DEGs. Moreover, the eno2- /35S:AtENO2-GFP line returned to the wild-type (WT) phenotype and was tolerant to drought and salt stresses. However, the eno2- /35S:AtMBP-1-GFP line was not able to recover the WT phenotype but it has a higher tolerance to drought and salt stresses. Results from this study demonstrate that AtENO2 is critical for the growth and development, and the AtMBP-1 coded by AtENO2 is important in tolerance of Arabidopsis to abiotic stresses.

Genome-Wide Identification and Expression Analyses of the Chitinases under Cold and Osmotic stress in Ammopiptanthus nanus.

Chitinase is a kind of hydrolase with chitin as a substrate and is proposed to play an essential role in plant defense system by functioning against fungal pathogens through degrading chitin. Recent studies indicated chitinase is also involved in abiotic stress response in plants, helping plants to survive in stressful environments. A. nanus, a rare evergreen broad-leaved shrub distrusted in deserts in Central Asia, exhibits a high level of tolerance to drought and low temperature stresses. To identify the chitinase gene involved in drought and low temperature responses in A. nanus, we performed genome-wide identification, classification, sequence alignment, and spatio-temporal gene expression analysis of the chitinases in A. nanus under osmotic and low temperature stress. A total of 32 chitinase genes belonging to glycosyl hydrolase 18 (GH18) and GH19 families were identified from A. nanus. Class III chitinases appear to be amplified quantitatively in A. nanus, and their genes carry less introns, indicating their involvement in stress response in A. nanus. The expression level of the majority of chitinases varied in leaves, stems, and roots, and regulated under environmental stress. Some chitinases, such as EVM0022783, EVM0020238, and EVM0003645, are strongly induced by low temperature and osmotic stress, and the MYC/ICE1 (inducer of CBF expression 1) binding sites in promoter regions may mediate the induction of these chitinases under stress. These chitinases might play key roles in the tolerance to these abiotic stress in A. nanus and have potential for biotechnological applications. This study provided important data for understanding the biological functions of chitinases in A. nanus.

Overexpression of the Jojoba Aquaporin Gene, ScPIP1, Enhances Drought and Salt Tolerance in Transgenic Arabidopsis.

Plasma membrane intrinsic proteins (PIPs) are a subfamily of aquaporin proteins located on plasma membranes where they facilitate the transport of water and small uncharged solutes. PIPs play an important role throughout plant development, and in response to abiotic stresses. Jojoba (Simmondsia chinensis (Link) Schneider), as a typical desert plant, tolerates drought, salinity and nutrient-poor soils. In this study, a PIP1 gene (ScPIP1) was cloned from jojoba and overexpressed in Arabidopsis thaliana. The expression of ScPIP1 at the transcriptional level was induced by polyethylene glycol (PEG) treatment. ScPIP1 overexpressed Arabidopsis plants exhibited higher germination rates, longer roots and higher survival rates compared to the wild-type plants under drought and salt stresses. The results of malonaldehyde (MDA), ion leakage (IL) and proline content measurements indicated that the improved drought and salt tolerance conferred by ScPIP1 was correlated with decreased membrane damage and improved osmotic adjustment. We assume that ScPIP1 may be applied to genetic engineering to improve plant tolerance based on the resistance effect in transgenic Arabidopsis overexpressing ScPIP1.

Quantitative Proteomic Analysis of the Response to Cold Stress in Jojoba, a Tropical Woody Crop.

Jojoba (Simmondsia chinensis) is a semi-arid, oil-producing industrial crop that have been widely cultivated in tropical arid region. Low temperature is one of the major environmental stress that impair jojoba's growth, development and yield and limit introduction of jojoba in the vast temperate arid areas. To get insight into the molecular mechanisms of the cold stress response of jojoba, a combined physiological and quantitative proteomic analysis was conducted. Under cold stress, the photosynthesis was repressed, the level of malondialdehyde (MDA), relative electrolyte leakage (REL), soluble sugars, superoxide dismutase (SOD) and phenylalanine ammonia-lyase (PAL) were increased in jojoba leaves. Of the 2821 proteins whose abundance were determined, a total of 109 differentially accumulated proteins (DAPs) were found and quantitative real time PCR (qRT-PCR) analysis of the coding genes for 7 randomly selected DAPs were performed for validation. The identified DAPs were involved in various physiological processes. Functional classification analysis revealed that photosynthesis, adjustment of cytoskeleton and cell wall, lipid metabolism and transport, reactive oxygen species (ROS) scavenging and carbohydrate metabolism were closely associated with the cold stress response. Some cold-induced proteins, such as cold-regulated 47 (COR47), staurosporin and temperature sensitive 3-like a (STT3a), phytyl ester synthase 1 (PES1) and copper/zinc superoxide dismutase 1, might play important roles in cold acclimation in jojoba seedlings. Our work provided important data to understand the plant response to the cold stress in tropical woody crops.

The Biological Significance and Regulatory Mechanism of c-Myc Binding Protein 1 (MBP-1).

Alternatively translated from the ENO gene and expressed in an array of vertebrate and plant tissues, c-Myc binding protein 1 (MBP-1) participates in the regulation of growth in organisms, their development and their environmental responses. As a transcriptional repressor of multiple proto-oncogenes, vertebrate MBP-1 interacts with other cellular factors to attenuate the proliferation and metastasis of lung, breast, esophageal, gastric, bone, prostrate, colorectal, and cervical cancer cells. Due to its tumor-suppressive property, MBP-1 and its downstream targets have been investigated as potential prognostic markers and therapeutic targets for various cancers. In plants, MBP-1 plays an integral role in regulating growth and development, fertility and abiotic stress responses. A better understanding of the functions and regulatory factors of MBP-1 in plants may advance current efforts to maximize plant resistance against drought, high salinity, low temperature, and oxidative stress, thus optimizing land use and crop yields. In this review article, we summarize the research advances in biological functions and mechanistic pathways underlying MBP-1, describe our current knowledge of the ENO product and propose future research directions on vertebrate health as well as plant growth, development and abiotic stress responses.

ENO2 knock-out mutants in Arabidopsis modify the regulation of the gene expression response to NaCl stress.

There is a growing awareness that some dual-function enzymes may provide a directly evidence that metabolism could feed into the regulation of gene expression via metabolic enzymes. However, the mechanism by which metabolic enzymes control gene expression to optimize plant stress responses remains largely unknown in Arabidopsis thaliana. LOS2/ENO2 is a bifunctional gene transcribed a functional RNA that translates a full-length version of the ENO2 protein and a truncated version of the MBP-1 protein. Here, we report that eno2 negatively regulates plant tolerance to salinity stress. NaCl treatment caused the death of the mutant eno2/eno2 homozygote earlier than the wild type (WT) Arabidopsis. To understand the mechanism by which the mutant eno2 had a lower NaCl tolerance, an analysis of the expressed sequence tag (EST) dataset from the WT and mutant eno2 Arabidopsis was conducted. Firstly, the most identified up- and down-regulated genes are senescence-associated gene 12 (SAG12) and isochorismate mutase-related gene, which are associated with salicylic acid (SA) inducible plant senescence and endogenous SA synthesis, respectively. Secondly, the differentially regulated by salt stress genes in mutant eno2 are largely enriched Gene Ontology(GO) terms associated with various kinds of response to stimulations. Thirdly, in the Kyoto Encyclopedia of Genes and Genomes (KEGG) mapping, we find that knocking out ENO2-influenced genes were most enriched into metabolite synthesis with extra plant-pathogen interaction pathway and plant hormone signal transduction pathway. Briefly, with the translation shifting function, LOS2/ENO2 not only influenced the genes involved in SA synthesis and transduction, but also influenced genes that participate in metabolite synthesis in cytoplasm and gene expression variation in nuclear under salt stress.

The molecular mechanisms of plant plasma membrane intrinsic proteins trafficking and stress response.

Plasma membrane intrinsic proteins (PIPs) are plant channel proteins located on the plasma membrane. PIPs transfer water, CO2 and small uncharged solutes through the plasma membrane. PIPs have high selectivity to substrates, suggestive of a central role in maintaining cellular water balance. The expression, activity and localization of PIPs are regulated at the transcriptional and post-translational levels, and also affected by environmental factors. Numerous studies indicate that the expression patterns and localizations of PIPs can change in response to abiotic stresses. In this review, we summarize the mechanisms of PIP trafficking, transcriptional and post-translational regulations, and abiotic stress responses. Moreover, we also discuss the current research trends and future directions on PIPs.

The Functional and Regulatory Mechanisms of the Thellungiella salsuginea Ascorbate Peroxidase 6 (TsAPX6) in Response to Salinity and Water Deficit Stresses.

Soil salinization is a resource and ecological problem in the world. Thellungiella salsuginea is becoming a new model plant because it resembles its relative species, Arabidopsis thaliana, in small genome and short life cycle. It is highly tolerant to salinity and drought stresses. Ascorbate peroxidase (APX) is an enzyme that clears H2O2 in plants. The function and molecular and regulation mechanisms of APX in T. salsuginea have rarely been reported. In this study, an APX gene, TsApx6, was cloned from T. salsuginea and its responses to abiotic stresses in transgenic Arabidopsis were studied. Under high salinity treatment, the expression of TsApx6 was significantly induced. Under drought treatment, overexpression of TsApx6 increased the survival rate and reduced leaf water loss rate in Arabidopsis. Compared to the wild type plants, high salinity treatment reduced the concentrations of MDA, H2O2 and proline but elevated the activities of APX, GPX, CAT and SOD in the TsApx6-overexpressing plants. Meanwhile, germination rate, cotyledon greening, and root length were improved in the transgenic plants compared to the wild type plants under salt and water deficit conditions. Based on these findings, TsApx6 has an important function in the resistance of plants to certain abiotic stresses. The TsApx6 promoter sequence was obtained using Genome Walking technology. Bioinformatics analysis indicated that it contains some cis-acting elements related to stress response. The treatments of salt, dehydration, and ABA induced the expression of Gus gene under the regulation of the TsApx6 promoter. Mutation analysis showed that the MBS motif present in the TsApx6 promoter might be a key negative regulatory element which has an important effect on the growth and developmental process of plants.

[The mechanism of histone lysine methylation of plant involved in gene expression and regulation].

Histone modification is one important sort of the epigenetic modifications, including acetylation, formylation, methylation, phosphorylation, ubiquitination and SUMOylation. By forming a complicated network, these modifications control the expression of genes. Histone methylation occurs mainly on the lysine residues, and plays a key role during flowering and stress response of plants, through changing the methylation status of lysine residues and the ratio of methylation. Triple-methylation of H3K4 promotes FLC expression but triple-methylation of H3K27 inhibits its expression. H3K4me3 activates the expression of PtdIns5P gene to initiate lipid synthesis signal pathway in response to drought stress. On the contrary, the low levels of H3K27me3 induce the expression of COR15A and ATGOLS3, which encode for low temperature protective proteins of chloroplast (Cor15am) and Galactional Synthase (GOLS), in order to resist cold stress. In this review, we summarize the molecular mechanisms of histone lysine methylation involved in DNA methylation, plant flowering and stress response.

[Expression regulation of plant ascorbate peroxidase and its tolerance to abiotic stresses].

Ascorbate peroxidase (APX), a type I heme peroxidase, catalyzes oxidation of ascorbic acid. It possesses a high degree of specificity to ascorbic acid. APX gene cluster consists of four sub-clusters: the gene clusters of cytosol, chloroplast, mitochondria, and peroxidase. As a key component of hydrogen peroxide detoxification system, the ascorbate-glutathione cycle, APX plays a vital role in the metabolism of H2O2 of plant cells. Studies showed that APX is one of the most important enzymes, which modulate the cellular H2O2 level in redox signaling system. The expression mechanisms of APX isoenzymes are quite complex. Briefly, cytosolic APX is regulated by a variety of signals; two chloroplastic APX isoenzymes are tissue-dependently regulated by alternative splicing. Generated APXs could regulate redox signaling in cells, which further boosts plants tolerance to abiotic stresses. This review focuses on recent advances concerning catalytic prop-erties, physiological function, and gene expressing regulation and abio-stress responding mechanism of APX.