The rice OsDIL gene plays a role in drought tolerance at vegetative and reproductive stages

Drought is one of the critical factors limiting reproductive yields of rice and other crops globally. However, little is known about the molecular mechanism underlying reproductive development under drought stress in rice. To explore the potential gene function for improving rice reproductive development under drought, a drought induced gene, Oryza sativa Drought-Induced LTP (OsDIL) encoding a lipid transfer protein, was identified from our microarray data and selected for further study. OsDIL was primarily expressed in the anther and mainly responsive to abiotic stresses, including drought, cold, NaCl, and stress-related plant hormone abscisic acid (ABA). Compared with wild type, the OsDIL-overexpressing transgenic rice plants were more tolerant to drought stress during vegetative development and showed less severe tapetal defects and fewer defective anther sacs when treated with drought at the reproductive stage. The expression levels of the drought-responsive genes RD22, SODA1, bZIP46 and POD, as well as the ABA synthetic gene ZEP1 were up-regulated in the OsDIL-overexpression lines but the ABA degradation gene ABAOX3 was down-regulated. Moreover, overexpression of OsDIL lessened the down-regulation by drought of anther developmental genes (OsC4, CYP704B2 and OsCP1), providing a mechanism supporting pollen fertility under drought. Overexpression of OsDIL significantly enhanced drought resistance in transgenic rice during reproductive development, while showing no phenotypic changes or yield penalty under normal conditions. Therefore, OsDIL is an excellent candidate gene for genetic improvement of crop yield in adaption to unfavorable environments.     

Biodegradation of the neonicotinoid insecticide thiamethoxam by the nitrogen-fixing and plant-growth-promoting rhizobacterium Ensifer adhaerens strain TMX-23

Thiamethoxam (THIA), a second generation neonicotinoid insecticide in the thianicotinyl subclass, is used worldwide. Environmental studies revealed that microbial degradation is the major mode of removal of this pesticide from soil. However, microbial transformation of THIA is poorly understood. In the present study, we isolated a bacterium able to degrade THIA from rhizosphere soil. The bacterium was identified as Ensifer adhaerens by its morphology and 16S ribosomal DNA sequence analysis. High-performance liquid chromatography and mass spectrometry analysis suggested that the major metabolic pathway of THIA in E. adhaerens TMX-23 involves the transformation of its N-nitroimino group (=N–NO₂) to N-nitrosoimino (=N–NO) and urea (=O) metabolites. E. adhaerens TMX-23 is a nitrogen-fixing bacterium harboring two types of nifH genes in its genome, one of which is 98 % identical to the nifH gene in the cyanobacterium Calothrix sp. MCC-3A. E. adhaerens TMX-23 released various plant-growth-promoting substances including indole-3-acetic acid, exopolysaccharides, ammonia, HCN, and siderophores. Inoculation of E. adhaerens TMX-23 onto soybean seeds (Glycine max L.) with NaCl at 50, 100, or 154 mmol/L increased the seed germination rate by 14, 21, and 30 %, respectively. THIA at 10 mg/L had beneficial effects on E. adhaerens TMX-23, enhancing growth of the bacterium and its production of salicylic acid, an important plant phytohormone associated with plant defense responses against abiotic stress. The nitrogen-fixing and plant-growth-promoting rhizobacterium E. adhaerens TMX-23, which is able to degrade THIA, has the potential for bioaugmentation as well as to promote growth of field crops in THIA-contaminated soil.     

Distinct and effective biotransformation of hexavalent chromium by a novel isolate under aerobic growth followed by facultative anaerobic incubation

A bacterial isolate (G161) with high Cr(VI)-reducing capacity was isolated from Cr(VI)-contaminated soil and identified as Leucobacter sp. on the basis of 16S rRNA gene sequence analysis. The isolate was a Gram-positive, aerobic rod. The hexavalent chromate-reducing capability of the isolate was investigated under three conditions of oxygen stress. The isolate was found to reduce Cr(VI) under all conditions but performed most effectively during aerobic growth followed by facultative anaerobic incubation. Under these conditions, the isolate tolerated K₂Cr₂O₇ concentrations up to 1,000 mg/l and completely reduced 400 mg/l K₂Cr₂O₇ within 96 h. The strain reduced Cr(VI) over a wide range of pH (6.0–11.0) and temperatures (15–45 °C) with optimum performance at pH?8.0 and 35 °C. The presence of other metals, such as Ca²⁺, Co²⁺, Cu²⁺, Mn²⁺, Ni²⁺, and Zn²⁺, induced no effect or else played a stimulatory role on Cr(VI)-reduction activity of the strain. The strain was tested for Cr(VI) removal in wastewaters and proved capable of completely reducing the contained Cr(VI). This is the novel report of a bacterial growth and Cr(VI)-reduction process under sequential aerobic growth and facultative anaerobic conditions. The study suggested that the isolate possesses a distinct capability for Cr(VI) reduction which could be harnessed for the detoxification of chromate-contaminated wastewaters.     

Rapid development of 36 polymorphic microsatellite markers for Tetranychus truncatus by transferring from Tetranychus urticae

Tetranychus truncatus Ehara is a phytophagous spider mite that is now one of the most important pests of agricultural and economic crops in East and Southeast Asia. However, population genetics and other studies of T. truncatus have been impeded by the lack of microsatellite markers, which are expensive and time-consuming to identify. Previous studies indicated a high potential of cross-amplification of microsatellites in Tetranychus species, meaning that the microsatellite flanking sequences are sufficiently homologous among Tetranychus species that the primers for one species may work in another species. Here, we tested 205 primer pairs designed from the whole genome sequence of Tetranychus urticae Koch, a sister species of T. truncatus, for microsatellite markers in three populations of T. truncatus in China (N = 94). About half (102) of these primer pairs yielded the desired PCR products, 36 of which revealed polymorphism in T. truncatus. Each of the 36 markers harbored between 2 and 23 alleles, with a mean polymorphic information content of 0.589 (0.119–0.922 range). The mean observed and expected heterozygosity across loci and the three populations were 0.468 and 0.628, respectively. Of the 36 primer pairs, 22 also worked in Tetranychus piercei, but only a few of them worked in T. ludeni and T. phaselus. Cross-amplification is thus a cost-effective way to develop microsatellite markers, which can be of great value in population genetics studies.     

Pip介导铜绿假单胞菌吩嗪基因簇phz2的表达

[目的]为了确定铜绿假单胞菌调控因子Pip对两个不同吩嗪合成基因簇(phz1和phz2)的具体调控方式与可能的调控机制.[方法]根据基因比对结果,采用同源重组技术构建Pip调控因子缺失突变株PA-PG以及克隆ip基因作互补分析;再以已构建的吩嗪基因簇缺失突变株PA-Z1G和PA-Z2K为受体菌,构建突变株PA-PD-Z1G和PA-PG-Z2K,测定并比较野生株及相关突变株的吩嗪-1-羧酸和绿脓菌素的合成量,推定Pip对两个不同吩嗪合成基因簇的调控方式.[结果]在GA培养基中,突变株PA-PG的吩嗪-1-羧酸和绿脓菌素都比野生型明显减少;互补分析显示,突变株PA-PG的吩嗪-1-羧酸和绿脓菌素都显著提高并恢复到野生株PAO1水平;突变株PA-Z1G的吩嗪-1-羧酸和绿脓菌素合成量因Pip缺失而显著减少;而突变株PA-Z2K的吩嗪-1-羧酸和绿脓菌素合成量在Pip缺失后仍保持不变.[结论]初步推定,转录调控因子Pip对铜绿假单胞菌吩嗪合成代谢的确具有促进作用;Pip通过正向调控吩嗪基因簇phz2的合成功能实现对吩嗪合成代谢的调控.     

Global Analysis of DNA Methylation Variation in Adipose Tissue from Twins Reveals Links to Disease-Associated Variants in Distal Regulatory Elements

Epigenetic modifications such as DNA methylation play a key role in gene regulation and disease susceptibility. However, little is known about the genome-wide frequency, localization, and function of methylation variation and how it is regulated by genetic and environmental factors. We utilized the Multiple Tissue Human Expression Resource (MuTHER) and generated Illumina 450K adipose methylome data from 648 twins. We found that individual CpGs had low variance and that variability was suppressed in promoters. We noted that DNA methylation variation was highly heritable (h²_median = 0.34) and that shared environmental effects correlated with metabolic phenotype-associated CpGs. Analysis of methylation quantitative-trait loci (metQTL) revealed that 28% of CpGs were associated with nearby SNPs, and when overlapping them with adipose expression quantitative-trait loci (eQTL) from the same individuals, we found that 6% of the loci played a role in regulating both gene expression and DNA methylation. These associations were bidirectional, but there were pronounced negative associations for promoter CpGs. Integration of metQTL with adipose reference epigenomes and disease associations revealed significant enrichment of metQTL overlapping metabolic-trait or disease loci in enhancers (the strongest effects were for high-density lipoprotein cholesterol and body mass index [BMI]). We followed up with the BMI SNP rs713586, a cg01884057 metQTL that overlaps an enhancer upstream of ADCY3, and used bisulphite sequencing to refine this region. Our results showed widespread population invariability yet sequence dependence on adipose DNA methylation but that incorporating maps of regulatory elements aid in linking CpG variation to gene regulation and disease risk in a tissue-dependent manner.     

Rhizobium qilianshanense sp. nov., a novel species isolated from root nodule of Oxytropis ochrocephala Bunge in China

During a study of the diversity and phylogeny of rhizobia isolated from root nodules of Oxytropis ochrocephala grown in the northwest of China, four strains were classified in the genus Rhizobium on the basis of their 16S rRNA gene sequences. These strains have identical 16S rRNA gene sequences, which showed a mean similarity of 94.4 % with the most closely related species, Rhizobium oryzae. Analysis of recA and glnA sequences showed that these strains have less than 88.1 and 88.7 % similarity with the defined species of Rhizobium, respectively. The genetic diversity revealed by ERIC-PCR fingerprinting indicated that the isolates correspond to different strains. Strain CCNWQLS01^T contains Q-10 as the predominant ubiquinone. The major fatty acids were identified as feature 8 (C18: 1ω7c and/or C18: 1ω6c; 67.2 %). Therefore, a novel species Rhizobium qilianshanense sp. nov. is proposed, and CCNWQLS01^T (= ACCC 05747^T = JCM 18337^T) is designated as the type strain.     

C-Myc negatively controls the tumor suppressor PTEN by upregulating miR-26a in glioblastoma multiforme cells

The c-Myc oncogene is amplified in many tumor types. It is an important regulator of cell proliferation and has been linked to altered miRNA expression, suggesting that c-Myc-regulated miRNAs might contribute to tumor progression. Although miR-26a has been reported to be upregulated in glioblastoma multiforme (GBM), the mechanism has not been established. We have shown that ectopic expression of miR-26a influenced cell proliferation by targeting PTEN, a tumor suppressor gene that is inactivated in many common malignancies, including GBM. Our findings suggest that c-Myc modulates genes associated with oncogenesis in GBM through deregulation of miRNAs via the c-Myc–miR-26a–PTEN signaling pathway. This may be of clinical relevance.     

Internal heavy atom effect of Au(III) and Pt(IV) on hypocrellin A for enhanced in vitro photodynamic therapy of cancer

Hypocrellin A (HA), an a natural perylene quinine photosensitizers (PSs), can chelate with heavy metal ions, including Au(III) and Pt(IV), to form a 1:2 complex, which exhibits enhanced ¹O₂ generation quantum yield through the increased intersystem crossing efficiency mediated by internal heavy atom effect. Besides, the chelate process greatly improved the water solubility of HA. Comparative studies with HA and complexes have demonstrated that the heavy-atom effect on HA molecules enhances the efficiency of in vitro photodynamic (PDT) efficacy.