Cassava is a major tropical food crop in the Euphorbiaceae family that has high carbohydrate production potential and adaptability to diverse environments. Here we present the draft genome sequences of a wild ancestor and a domesticated variety of cassava and comparative analyses with a partial inbred line. We identify 1,584 and 1,678 gene models specific to the wild and domesticated varieties, respectively, and discover high heterozygosity and millions of single-nucleotide variations. Our analyses reveal that genes involved in photosynthesis, starch accumulation and abiotic stresses have been positively selected, whereas those involved in cell wall biosynthesis and secondary metabolism, including cyanogenic glucoside formation, have been negatively selected in the cultivated varieties, reflecting the result of natural selection and domestication. Differences in microRNA genes and retrotransposon regulation could partly explain an increased carbon flux towards starch accumulation and reduced cyanogenic glucoside accumulation in domesticated cassava. These results may contribute to genetic improvement of cassava through better understanding of its biology.
Background: BH3-mimetic molecules possessing potential anticancer activity are able to inhibit antiapoptotic Bcl-2 family proteins. Results: AT101 induced apoptosis in chemoresistant ovarian cancer cells. Conclusion: Smac-mediated Bax activation is a determinant of AT101-induced apoptosis. Significance: We provide a theoretical basis for AT101 as a potential therapeutic agent in the treatment of ovarian cancer.
BH3 (Bcl-2 homology domain 3)-only proteins have an important role in the cisplatin resistance of cells. However, the effect of BH3-only proteins on cisplatin-resistant ovarian cancer cells has not been thoroughly elucidated. Our results from the present study indicate that Puma plays a critical role in the apoptosis of chemo-resistant ovarian cancer cells treated with BetA (betulinic acid). The reduction of Puma expression inhibits Bax activation and apoptosis. However, p53 gene silencing has little effect on Puma activation. Further experiments demonstrated that Akt-mediated FoxO3a (forkhead box O3a) nuclear translocation and the JNK (c-Jun N-terminal kinase)/c-Jun pathway only partially trigger Puma induction and apoptosis, whereas dominant-negative c-Jun expression with FoxO3a reduction completely inhibits Puma expression and cell death. Furthermore, our results suggest that JNK regulates the Akt/FoxO3a signalling pathway. Therefore the dual effect of JNK can efficiently trigger Puma activation and apoptosis in chemoresistant cells. Taken together, our results demonstrate the role of Puma in BetA-induced apoptosis and the molecular mechanisms of Puma expression regulated by BetA during ovarian cancer cell apoptosis. Our findings suggest that the JNK-potentiated Akt/FoxO3a and JNK-mediated c-Jun pathways co-operatively trigger Puma expression, which determines the threshold for overcoming chemoresistance in ovarian cancer cells.
Glucose sensitive membrane (GSM) consists of glucose oxidases (GODs) and matrix material (for example, polyacrylamide gel). In this paper, we have investigated the optical property and adsorption isotherms of a GSM based on a terminal reflection optical fiber SPR sensor. Firstly, we reported the fabrication of one kind of GSM which was made of immobilized GODs on SiO2 nanoparticles and PAM gel. Then, we investigated the effects of GSM thickness, GOD content, solution pH and ambient temperature on the reflected spectrum of sensor, and the optimum parameters of the sensor, such as, GSM thickness of 12 times pulling, 4 mg/mL of GOD content in GSM, 7.0 of solution pH and 40 °C of measuring temperature were obtained. Thirdly, we measured the wavelength shifts of the optimized SPR sensor in the solutions with different glucose concentrations. As the glucose concentration increases from 0 to 80 mg/dL, the resonance wavelength decreases approximately linearly and the corresponding sensitivity is about 0.14 nm/(mg/dL). Finally, we investigated the RI of the GSM, the concentration of glucose into GSM and the adsorption isotherm of GSM by the combination of SPR experiment data, theoretical simulation and Gladstone-Dale mixing rule. As the glucose concentration is in the region of [0, 80] mg/dL, the adsorption of GSM for glucose can be explained by the Freundlich isotherm model. As the glucose concentration is in the region of [120, 500] mg/dL, the Langmuir isotherm model is more suitable to describe the adsorption process of GSM for glucose.
Reverse transcription quantitative real-time polymerase chain reaction (real-time PCR, also referred to as quantitative RT-PCR or RT-qPCR) is a highly sensitive and high-throughput method used to study gene expression. Despite the numerous advantages of RT-qPCR, its accuracy is strongly influenced by the stability of internal reference genes used for normalizations. To date, few studies on the identification of reference genes have been performed on cassava (Manihot esculenta Crantz). Therefore, we selected 26 candidate reference genes mainly via the three following channels: reference genes used in previous studies on cassava, the orthologs of the most stable Arabidopsis genes, and the sequences obtained from 32 cassava transcriptome sequence data. Then, we employed ABI 7900 HT and SYBR Green PCR mix to assess the expression of these genes in 21 materials obtained from various cassava samples under different developmental and environmental conditions. The stability of gene expression was analyzed using two statistical algorithms, namely geNorm and NormFinder. geNorm software suggests the combination of cassava4.1_017977 and cassava4.1_006391 as sufficient reference genes for major cassava samples, the union of cassava4.1_014335 and cassava4.1_006884 as best choice for drought stressed samples, and the association of cassava4.1_012496 and cassava4.1_006391 as optimal choice for normally grown samples. NormFinder software recommends cassava4.1_006884 or cassava4.1_006776 as superior reference for qPCR analysis of different materials and organs of drought stressed or normally grown cassava, respectively. Results provide an important resource for cassava reference genes under specific conditions. The limitations of these findings were also discussed. Furthermore, we suggested some strategies that may be used to select candidate reference genes.
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