High boron stress leads to sugar beet (Beta vulgaris L.) toxicity by disrupting photosystem â ¡.

This sugar beet acts as a soil remediator in areas where there are high levels of boron (B) in the soil, since it has a high requirement of boron (B) for growth, and has strong resistance to high B levels. Although B toxicity in different plants has been widely researched, little is known about the response of photosystem II (PSII) activity in sugar beet leaves to B toxicity at present. To clarify the growth and photosynthetic physiological response of sugar beet to B toxicity, the effects of different concentrations of H3BO3 (0.05, 1.5, 2.5,3.5 mM) on the growth, photosynthetic characteristics and antioxidant defense system of sugar beet seedlings were investigated by hydroponic experiments. In the present study, high B stress inhibited the growth of sugar beet and significantly decreased the biomass of the plants. There was a remarkable increase in the accumulation of B in the shoots, which affected photosynthesis and decreased the photosynthetic pigments. As B toxicity increased, leaf PSII activities and maximum photochemical efficiency of PSII (Fv/Fm) showed a tendency to decrease; at the same time, the photosynthetic performance index based on absorbed light energy (PIABS) decreased as well. Meanwhile, the energy allocation parameters of the PSII reaction center were changed, the light energy utilization capacity and the energy used for electron transfer were reduced and the thermal dissipation was increased at the same time. Furthermore, B toxicity decreased catalase (CAT) activity, increased peroxidase (POD) and superoxide dismutase (SOD) activities, and increased malondialdehyde (MDA) accumulation. According to the results obtained in this study, high B concentrations reduced the rate of photosynthesis and fluorescence, thus weakened antioxidant defense systems, and therefore inhibited the growth of sugar beet plants. Thus, in high B areas, sugar beet possesses excellent tolerance to high B levels and has a high B translocation capacity, so it can be used as a phytoremediation tool. This study provides a basis for the feasibility of sugar beet resistant to high B environments.

Genome-wide identification and expression analysis of the WRKY transcription factor family in flax (Linum usitatissimum L.).

BACKGROUND: Members of the WRKY protein family, one of the largest transcription factor families in plants, are involved in plant growth and development, signal transduction, senescence, and stress resistance. However, little information is available about WRKY transcription factors in flax (Linum usitatissimum L.). RESULTS: In this study, comprehensive genome-wide characterization of the flax WRKY gene family was conducted that led to prediction of 102 LuWRKY genes. Based on bioinformatics-based predictions of structural and phylogenetic features of encoded LuWRKY proteins, 95 LuWRKYs were classified into three main groups (Group I, II, and III); Group II LuWRKYs were further assigned to five subgroups (IIa-e), while seven unique LuWRKYs (LuWRKYs 96-102) could not be assigned to any group. Most LuWRKY proteins within a given subgroup shared similar motif compositions, while a high degree of motif composition variability was apparent between subgroups. Using RNA-seq data, expression patterns of the 102 predicted LuWRKY genes were also investigated. Expression profiling data demonstrated that most genes associated with cellulose, hemicellulose, or lignin content were predominantly expressed in stems, roots, and less in leaves. However, most genes associated with stress responses were predominantly expressed in leaves and exhibited distinctly higher expression levels in developmental stages 1 and 8 than during other stages. CONCLUSIONS: Ultimately, the present study provides a comprehensive analysis of predicted flax WRKY family genes to guide future investigations to reveal functions of LuWRKY proteins during plant growth, development, and stress responses.

Development of a specific AFLP-based SCAR marker for Chinese Race 34MKG of Puccinia graminis f. sp. tritici.

Wheat stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a fungus that causes the devastating fungalwheat stem rust disease in wheat production. Rapid identification of the physiological races of Pgt are very importance for the prevention of wheat stem rust. In this paper we developed a molecular method to identify the most prevalent race of Pgt, as a supplement for traditionally used host-specific methods. Amplified fragment length polymorphism (AFLP) was employed as a means of analyzing DNA polymorphisms in six common physiological races of Pgt in China and Ug99. In total, 64 pairs of primers were used for AFLP screening of race-specific molecular markers. One primer pair-namely, E7/M7 (5'-GACTGCGTACCAATTCG G-3'/5'-GATGAGTCCTGAGTAACGG-3')-yielded a unique band for the race 34MKG that was purified and cloned into the pGEM-T vector for sequencing. We then designed a new primer pairs (sequence-characterized amplified region marker) to amplify the 171-bp fragment and confirmed that the marker was highly specific for 34MKG. These results provide a new tool for monitoring different races of Pgt for improved control of wheat stem rust in China.

Rhodococcus daqingensis sp. nov., isolated from petroleum-contaminated soil.

A novel Gram-stain positive, aerobic, non-motile bacterial strain, designated Z1T, was isolated from a sample of petroleum-contaminated soil collected in Daqing, Heilongjiang province, China and characterised with a series of taxonomic approaches. The morphological and chemotaxonomic properties of the isolate were typical of those of members of the genus Rhodococcus. Phylogenetic analyses based on 16S rRNA gene sequences showed that strain Z1T belongs to the genus Rhodococcus and clustered with Rhodococcus maanshanensis DSM 44675T (99.2%, sequence similarity) and Rhodococcus tukisamuensis JCM 11308T (97.9%), respectively. However, the DNA-DNA hybridizations between strain Z1T and R. maanshanensis DSM 44675T and R. tukisamuensis JCM 11308T were both less than 70%. The optimal growth temperature and pH for strain Z1T were found to be at 28 °C and at pH 7.0. The peptidoglycan was found to contain meso-diaminopimelic acid; arabinose, galactose and glucose were detected as diagnostic sugars. The main polar lipids were identified as diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, phosphatidylinositol mannoside and an unidentified lipid; MK-8(H2) was found as the major menaquinone. The major fatty acids were identified as C16:0, 10-methyl C18:0 and C18:1ω9c. Mycolic acids were found to be present. The G + C content of the genomic DNA was determined to be 66.7 mol%. Based on a comparative analysis of phenotypic and genotypic characteristics, in combination with DNA-DNA hybridization results, strain Z1T can be distinguished from the type strains of its two close neighbours as a novel species of the genus Rhodococcus, for which the name Rhodococcus daqingensis sp. nov. is proposed. The type strain is Z1T (= CGMCC 1.13630T = DSM 107227T).

Exogenous Application of Phytohormones Promotes Growth and Regulates Expression of Wood Formation-Related Genes in Populus simonii × P. nigra.

Although phytohormones are known to be important signal molecules involved in wood formation, their roles are still largely unclear. Here, Populus simonii × P. nigra seedlings were treated with different concentrations of exogenous phytohormones, indole-3-acetic acid (IAA), gibberellin (GA3), and brassinosteroid (BR), and the effects of phytohormones on growth were investigated. Next, 27 genes with known roles in wood formation were selected for qPCR analysis to determine tissue-specificity and timing of responses to phytohormone treatments. Compared to the control, most IAA, GA3, and BR concentrations significantly increased seedling height. Meanwhile, IAA induced significant seedling stem diameter and cellulose content increases that peaked at 3 and 30 mg·L-1, respectively. Significant increase in cellulose content was also observed in seedlings treated with 100 mg·L-1 GA3. Neither stem diameter nor cellulose content of seedlings were affected by BR treatment significantly, although slight effects were observed. Anatomical measurements demonstrated improved xylem, but not phloem, development in IAA- and BR-treated seedlings. Most gene expression patterns induced by IAA, GA3, and BR differed among tissues. Many IAA response genes were also regulated by GA3, while BR-induced transcription was weaker and slower in Populus than for IAA and GA3. These results reveal the roles played by phytohormones in plant growth and lay the foundation for exploring molecular regulatory mechanisms of wood formation in Populus.

Identification and characterization of miRNAs and targets in flax (Linum usitatissimum) under saline, alkaline, and saline-alkaline stresses.

BACKGROUND: MicroRNAs (miRNAs) play a critical role in responses to biotic and abiotic stress and have been characterized in a large number of plant species. Although flax (Linum usitatissimum L.) is one of the most important fiber and oil crops worldwide, no reports have been published describing flax miRNAs (Lus-miRNAs) induced in response to saline, alkaline, and saline-alkaline stresses. RESULTS: In this work, combined small RNA and degradome deep sequencing was used to analyze flax libraries constructed after alkaline-salt stress (AS2), neutral salt stress (NSS), alkaline stress (AS), and the non-stressed control (CK). From the CK, AS, AS2, and NSS libraries, a total of 118, 119, 122, and 120 known Lus-miRNAs and 233, 213, 211, and 212 novel Lus-miRNAs were isolated, respectively. After assessment of differential expression profiles, 17 known Lus-miRNAs and 36 novel Lus-miRNAs were selected and used to predict putative target genes. Gene ontology term enrichment analysis revealed target genes that were involved in responses to stimuli, including signaling and catalytic activity. Eight Lus-miRNAs were selected for analysis using qRT-PCR to confirm the accuracy and reliability of the miRNA-seq results. The qRT-PCR results showed that changes in stress-induced expression profiles of these miRNAs mirrored expression trends observed using miRNA-seq. Degradome sequencing and transcriptome profiling showed that expression of 29 miRNA-target pairs displayed inverse expression patterns under saline, alkaline, and saline-alkaline stresses. From the target prediction analysis, the miR398a-targeted gene codes for a copper/zinc superoxide dismutase, and the miR530 has been shown to explicitly target WRKY family transcription factors, which suggesting that these two micRNAs and their targets may significant involve in the saline, alkaline, and saline-alkaline stress response in flax. CONCLUSIONS: Identification and characterization of flax miRNAs, their target genes, functional annotations, and gene expression patterns are reported in this work. These findings will enhance our understanding of flax miRNA regulatory mechanisms under saline, alkaline, and saline-alkaline stresses and provide a foundation for future elucidation of the specific functions of these miRNAs.

Insights into physiological and molecular mechanisms underlying efficient utilization of boron in different boron efficient Beta vulgaris L. varieties.

Boron (B) deficiency and consequent limitation of plant yield and quality, particularly of sugar beet (Beta vulgaris L.) has emerged as a maior problem,which is exacerbating due to cultivar dependent variability in B deficiency tolerance. Pertinently, the current study was designed to elucidate the physiological and molecular mechanisms of B deficiency tolerance of sugar beet varieties KWS1197 (B-efficient variety) and KWS0143 (B-inefficient variety). A hydroponic experiment was conducted employing two B levels B0.1 (0.1 µM L-1 H3BO3, deficiency) and B50 (50 µM L-1 H3BO3, adequacy). Boron deficiency greatly inhibited root elongation and dry matter accumulation; however, formation of lateral roots stimulated and average root diameter was increased. Results exhibited that by up-regulating the expression of NIP5-1, NIP6-1, and BOR2, and suppressing the expression of BOR4, cultivar KWS1197, in contrast to KWS0143, managed to transfer sufficient amount of B to the aboveground plant parts, facilitating its effective absorption and utilization. Accumulation of malondialdehyde (MDA) and reactive oxygen species (ROS) was also mellowed in KWS1197, as well as the oxidative damage to root cells via preservation of the antioxidant enzyme system. Additionally, the expression of essential enzymes for biosynthesis of phytohormone (PYR/PYL) and lignin (COMT, POX, and CCoAOMT) were found to be highly up-regulated in KWS1197. Deductively, through effective B absorption and transportation, balanced nutrient accumulation, and an activated antioxidant enzyme system, B-efficient cultivars may cope with B deficiency while retaining a superior cellular structure to enable root development.

Study on phytotoxicity evaluation and physiological properties of nicosulfuron on sugar beet (Beta vulgaris L.).

Nicosulfuron is an herbicide widely used in corn fields. In northeast China, sugar beet is often planted adjacent to corn, resulting in frequent phytotoxicity of nicosulfuron drift in sugar beet fields. This study was conducted by spraying nicosulfuron to assess the phytotoxicity and clarify the mechanism of nicosulfuron toxicity on sugar beet. The results showed that nicosulfuron impaired growth and development by reducing photosynthetic capacity and disrupting antioxidant systems at a lethal dose of 81.83 g a.i. ha-1. Nicosulfuron damaged the function of photosynthetic system II (PSII), lowered photosynthetic pigment content, and inhibited photosynthetic efficiency. Compared with the control, the electron transfer of PSII was blocked. The ability of PSII reaction centers to capture and utilize light energy was reduced, resulting in a weakened photosynthetic capacity. The maximum net photosynthetic rate (Amax), light saturation point (LSP), and apparent quantum yield (AQY) decreased gradually as the nicosulfuron dose increased, whereas the light compensation point (LCP) and dark respiration (Rd) increased. Nicosulfuron led to reactive oxygen species (ROS) accumulation in sugar beet leaf, a significant rise in malondialdehyde (MDA) content, electrolytic leakage (EL), and considerable oxidative damage to the antioxidant system. This study is beneficial for elucidating the effects of nicosulfuron toxicity on sugar beet, in terms of phytotoxicity, photosynthetic physiology, and antioxidative defense system.

Effect of boron deficiency on the photosynthetic performance of sugar beet cultivars with contrasting boron efficiencies.

Boron (B) deficiency severely affects the quality of sugar beet production, and the employment of nutrient-efficient varieties for cultivation is a crucial way to solve environmental and resource-based problems. However, the aspect of leaf photosynthetic performance among B-efficient sugar beet cultivars remains uncertain. The B deficient and B-sufficient treatments were conducted in the experiment using KWS1197 (B-efficient) and KWS0143 (B-inefficient) sugar beet cultivars as study materials. The objective of the present study was to determine the impacts of B deficiency on leaf phenotype, photosynthetic capacity, chloroplast structure, and photochemical efficiency of the contrasting B-efficiency sugar beet cultivars. The results indicated that the growth of sugar beet leaves were dramatically restricted, the net photosynthetic rate was significantly decreased, and the energy flux, quantum yield, and flux ratio of PSII reaction centers were adversely affected under B deficiency. Compared to the KWS0143 cultivar, the average leaf area ratio of the KWS1197 cultivar experienced less impact, and its leaf mass ratio (LMR) increased by 26.82% under B deficiency, whereas for the KWS0143 cultivar, the increase was only 2.50%. Meanwhile, the light energy capture and utilization capacity of PSII reaction centers and the proportion of absorbed light energy used for electron transfer were higher by 3.42% under B deficiency; KWS1197 cultivar managed to alleviate the photo-oxidative damage, which results from excessive absorbed energy (ABS/RC), by increasing the dissipated energy (DIo/RC). Therefore, in response to B deprivation, the KWS1197 cultivar demonstrated greater adaptability in terms of morphological indices and photosynthetic functions, which not only explains the improved performance but also renders the measured parameters as the key features for varietal selection, providing a theoretical basis for the utilization of efficient sugar beet cultivars in future.

Transcriptome analysis reveals the molecular mechanism of boron deficiency tolerance in leaves of boron-efficient Beta vulgaris seedlings.

Sugar beet (Beta vulgaris L.) has a high demand for B, and B deficiency inhibits normal growth and productivity. However, there is a lack of information on how B deficiency affects the growth of beet at the transcriptome level, and the factors that govern B utilisation efficiency. This study aimed to identify the genes differentially expressed under B deficiency and those that underlie the mechanisms of efficient B use in two sugar beet cultivars. Accordingly, B-efficient (H, KWS1197) and B-inefficient (L, KWS0143) sugar beet cultivars were used, and two levels of boron were employed in the hydroponic experiments: B0.1 (0.1 µM B, deficiency) and B50 (50 µM B, CK). The results showed that B deficiency inhibited leaf growth, significantly reduced B concentration and B transfer coefficient, and increased peroxidase (POD) activity and malondialdehyde and proline content. The transcriptome data showed that the B-efficient variety exhibited more differentially expressed genes than the B-inefficient variety. Metabolic pathways were the most critical pathways involved in the B deficiency response. The expression of POD, bHLH, WRKY transcription factors, and nodulin26-like intrinsic protein (NIP5;1) were upregulated in the KWS1197 variety. In conclusion, the KWS1197 variety had physiological advantages and a highly efficient B utilisation molecular mechanism, contributing to a high B deficiency tolerance. This study provides a theoretical basis for the adaptation mechanism to B deficiency in sugar beets.

Improvement of germinated brown rice quality with autoclaving treatment.

Germinated brown rice (GBR) is a popular functional food containing considerable amounts of beneficial nutrients and bioactive compounds. Here, autoclaving at 115°C for 20 min was employed to process GBR (AGBR) to evaluate the effect of autoclaving on the nutritional and health function of GBR in microstructure, taste value, aroma, as well as the physiological ingredients. The results showed that autoclaving treatment influenced the starch gelatinization and aroma to improve the taste of cooked AGBR. Autoclaving treatment significantly increased the gamma-aminobutyric acid (GABA) and ferulic acid levels of AGBR (p < .05). In addition, consuming AGBR for 1 month significantly decreased the fasting plasma glucose (FPG), 0.5, 1, and 2 hr postprandial plasma glucose (PPG), triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c), and low-density lipoprotein cholesterol (LDL-c) in metabolic syndrome (MS) patients (p < .05). Therefore, autoclaving treatment, as a promising processing strategy, may both improve the sensory attributes and the nutrition of GBR.

The complete mitochondrial genome of Yao silkworm (Bombyx mori).

Here, we describe the first complete mitochondrial genome of Yao silkworm, a unique silkworm resource native at Guangxi, China. This circular molecule is 15,656 bp long and contains the typical set of 37 genes (13 protein-coding genes, two ribosomal RNA genes, and 22 transfer RNA genes) and one non-coding A + T-rich region of 494 bp long. The genome organization and gene arrangement are identical to those observed in all available Bombyx mori strains. The phylogenetic tree inferred from Bayesian inference provides a molecular evidence that Yao silkworm belongs to the domestic silkworm (B. mori), rather than a novel silkworm species.

OFP1 Interaction with ATH1 Regulates Stem Growth, Flowering Time and Flower Basal Boundary Formation in Arabidopsis.

Ovate Family Protein1 (OFP1) is a regulator, and it is suspected to be involved in plant growth and development. Meanwhile, Arabidopsis Thaliana Homeobox (ATH1), a BEL1-like homeodomain (HD) transcription factor, is known to be involved in regulating stem growth, flowering time and flower basal boundary development in Arabidopsis. Previous large-scale yeast two-hybrid studies suggest that ATH1 possibly interact with OFP1, but this interaction is yet unverified. In our study, the interaction of OFP1 with ATH1 was verified using a directional yeast two-hybrid system and bimolecular fluorescence complementation (BiFC). Our results also demonstrated that the OFP1-ATH1 interaction is mainly controlled by the HD domain of ATH1. Meanwhile, we found that ATH1 plays the role of transcriptional repressor to regulate plant development and that OFP1 can enhance ATH1 repression function. Regardless of the mechanism, a putative functional role of ATH1-OFP1 may be to regulate the expression of the both the GA20ox1 gene, which is involved in gibberellin (GA) biosynthesis and control of stem elongation, and the Flowering Locus C (FLC) gene, which inhibits transition to flowering. Ultimately, the regulatory functional mechanism of OFP1-ATH1 may be complicated and diverse according to our results, and this work lays groundwork for further understanding of a unique and important protein⁻protein interaction that influences flowering time, stem development, and flower basal boundary development in plants.

Identification of differentially expressed genes in flax (Linum usitatissimum L.) under saline-alkaline stress by digital gene expression.

The salinization and alkalization of soil are widespread environmental problems, and alkaline salt stress is more destructive than neutral salt stress. Therefore, understanding the mechanism of plant tolerance to saline-alkaline stress has become a major challenge. However, little attention has been paid to the mechanism of plant alkaline salt tolerance. In this study, gene expression profiling of flax was analyzed under alkaline-salt stress (AS2), neutral salt stress (NSS) and alkaline stress (AS) by digital gene expression. Three-week-old flax seedlings were placed in 25 mM Na2CO3 (pH11.6) (AS2), 50mM NaCl (NSS) and NaOH (pH11.6) (AS) for 18 h. There were 7736, 1566 and 454 differentially expressed genes in AS2, NSS and AS compared to CK, respectively. The GO category gene enrichment analysis revealed that photosynthesis was particularly affected in AS2, carbohydrate metabolism was particularly affected in NSS, and the response to biotic stimulus was particularly affected in AS. We also analyzed the expression pattern of five categories of genes including transcription factors, signaling transduction proteins, phytohormones, reactive oxygen species proteins and transporters under these three stresses. Some key regulatory gene families involved in abiotic stress, such as WRKY, MAPKKK, ABA, PrxR and ion channels, were differentially expressed. Compared with NSS and AS, AS2 triggered more differentially expressed genes and special pathways, indicating that the mechanism of AS2 was more complex than NSS and AS. To the best of our knowledge, this was the first transcriptome analysis of flax in response to saline-alkaline stress. These data indicate that common and diverse features of saline-alkaline stress provide novel insights into the molecular mechanisms of plant saline-alkaline tolerance and offer a number of candidate genes as potential markers of tolerance to saline-alkaline stress.