Sexual reproduction in higher plants I: fertilization and the initiation of zygotic program

Sexual plant reproduction is a critical developmental step in the life cycle of higher plants, to allow maternal and paternal genes to be transmitted in a highly regulated manner to the next generation. During evolution, a whole set of signal transduction machinery is developed by plants to ensure an error-free recognition between male and female gametes and initiation of zygotic program. In the past few years, the molecular machineries underlying this biological process have been elucidated, particularly on the importance of synergid cells in pollen tube guidance, the Ca⁺⁺ spike as the immediate response of fertilization and the epigenetic regulation of parental gene expressions in early zygotic embryogenesis. This review outlines the most recent development in this area.     

Lactic Acid Production from Pretreated Hydrolysates of Corn Stover by a Newly Developed Bacillus coagulans Strain

An inhibitor-tolerance strain, Bacillus coagulans GKN316, was developed through atmospheric and room temperature plasma (ARTP) mutation and evolution experiment in condensed dilute-acid hydrolysate (CDH) of corn stover. The fermentabilities of other hydrolysates with B. coagulans GKN316 and the parental strain B. coagulans NL01 were assessed. When using condensed acid-catalyzed steam-exploded hydrolysate (CASEH), condensed acid-catalyzed liquid hot water hydrolysate (CALH) and condensed acid-catalyzed sulfite hydrolysate (CASH) as substrates, the concentration of lactic acid reached 45.39, 16.83, and 18.71 g/L by B. coagulans GKN316, respectively. But for B. coagulans NL01, only CASEH could be directly fermented to produce 15.47 g/L lactic acid. The individual inhibitory effect of furfural, 5-hydroxymethylfurfural (HMF), vanillin, syringaldehyde and p-hydroxybenzaldehyde (pHBal) on xylose utilization by B. coagulans GKN316 was also studied. The strain B. coagulans GKN316 could effectively convert these toxic inhibitors to the less toxic corresponding alcohols in situ. These results suggested that B. coagulans GKN316 was well suited to production of lactic acid from undetoxified lignocellulosic hydrolysates.     

Two Hox cofactors, the Meis/Hth homolog UNC-62 and the Pbx/Exd homolog CEH-20, function together during C. elegans postembryonic mesodermal development

The TALE homeodomain-containing PBC and MEIS proteins play multiple roles during metazoan development. Mutations in these proteins can cause various disorders, including cancer. In this study, we examined the roles of MEIS proteins in mesoderm development in C. elegans using the postembryonic mesodermal M lineage as a model system. We found that the MEIS protein UNC-62 plays essential roles in regulating cell fate specification and differentiation in the M lineage. Furthermore, UNC-62 appears to function together with the PBC protein CEH-20 in regulating these processes. Both unc-62 and ceh-20 have overlapping expression patterns within and outside of the M lineage, and they share physical and regulatory interactions. In particular, we found that ceh-20 is genetically required for the promoter activity of unc-62, providing evidence for another layer of regulatory interactions between MEIS and PBC proteins.     

Aspirin Use and Lung Cancer Risk: A Possible Relationship? Evidence from an Updated Meta-Analysis

Background and Purpose

Growing evidence has emerged and controversial results reported on possible relationship between aspirin use and lung cancer risk. We, therefore, conducted this updated and comprehensive meta-analysis to evaluate this issue, with focus on dose-risk and duration-risk relationships.

Methods

We searched electronic databases including PUBMED, EMBASE and Cochrane library to identify eligible studies. Relative risk (RR) and its 95% confidence interval (CI) were used for cohort studies, while odds ratio (OR) were employed for case-control studies. The random effects and fixed effects models were used for analyses.

Results

18 studies were identified including 19835 lung cancer cases, which were eligible for inclusion in the present meta-analysis. Pooled data from case-control studies showed a significant inverse association between regular aspirin use and lung cancer risk. But for cohort studies, insignificant association was detected with little evidence of heterogeneity (RR: 1.05, 95%CI: 0.95 – 1.16; I²: 10.3%, p value: 0.351). In case-control studies, standard aspirin use (>325mg) was related to lower lung cancer incidence, compared with low-dose aspirin use (75–100mg). A similar trend was observed in cohort studies. Besides, when analysis was restricted to long time regular aspirin use (>5 years), insignificant results were reported in both cohort and case-control studies. Finally, regular aspirin use might result in higher reduction of non-small cell lung cancer incidence among men.

Conclusions

Our findings do not support the protective effect of regular aspirin use on lung cancer risk. Long time aspirin use, sex, dose and type of lung cancer might alter the effect of aspirin use on lung cancer risk. More well-designed studies are needed to further clarify these associations.     

Effects of salinity on cell growth and docosahexaenoic acid content of the heterotrophic marine microalga Crypthecodinium cohnii

The effects of salinity on cell growth and docosahexaenoic acid (DHA) content of three marine microalgal strains, Crythecodinium cohnii ATCC 30556, C. cohnii ATCC 50051 and C. cohnii RJH were investigated. The lag phases of the three strains increased with increasing salinity in Porphyridium medium. The specific growth rate of C. cohnii ATCC 30556 was the highest at 9 g L⁻¹ NaCl while the other two strains had their highest specific growth rates at 5 g L⁻¹ NaCl. The highest cell dry weight concentrations of 2.51 g L⁻¹ and 1.56 g L⁻¹ were achieved at 9 g L⁻¹ NaCl for C. cohnii ATCC 30556 and ATCC 50051, respectively, while the highest dry weight concentration of 2.49 g L⁻¹ was achieved at 5 g L⁻¹ NaCl for C. cohnii RJH. The highest cell growth yield coefficient on glucose was 0.5 g g⁻¹ for both C. cohnii ATCC 30556 and C. cohnii RJH and 0.45 g g⁻¹ for C. cohnii ATCC 50051. All three strains responded to the change of salinity by modifying their cellular fatty acid compositions. At 9 g L⁻¹ NaCl, C. cohnii ATCC 30556 had the highest total fatty acid content and DHA (C22:6) proportion. In contrast, C. cohnii ATCC 50051 and C. cohnii RJH had the highest DHA content at 5 g L⁻¹ NaCl. C. cohnii ATCC 30556 and ATCC 50051 had the highest DHA yield (131.55 and 68.24 mg L⁻¹ respectively) at 9 g L⁻¹ NaCl while C. cohnii RJH had the highest DHA yield (128.83 mg L⁻¹) at 5 g L⁻¹ NaCl. Received 27 May 1999/ Accepted in revised form 27 August 1999     

Metabolic engineering of Corynebacterium glutamicum for increasing the production of l-ornithine by increasing NADPH availability

The experiments presented here were based on the conclusions of our previous proteomic analysis. Increasing the availability of glutamate by overexpression of the genes encoding enzymes in the l-ornithine biosynthesis pathway upstream of glutamate and disruption of speE, which encodes spermidine synthase, improved l-ornithine production by Corynebacterium glutamicum. Production of l-ornithine requires 2 moles of NADPH per mole of l-ornithine. Thus, the effect of NADPH availability on l-ornithine production was also investigated. Expression of Clostridium acetobutylicum gapC, which encodes NADP-dependent glyceraldehyde-3-phosphate dehydrogenase, and Bacillus subtilis rocG, which encodes NAD-dependent glutamate dehydrogenase, led to an increase of l-ornithine concentration caused by greater availability of NADPH. Quantitative real-time PCR analysis demonstrates that the increased levels of NADPH resulted from the expression of the gapC or rocG gene rather than that of genes (gnd, icd, and ppnK) involved in NADPH biosynthesis. The resulting strain, C. glutamicum ΔAPRE::rocG, produced 14.84 g l^?1 of l-ornithine. This strategy of overexpression of gapC and rocG will be useful for improving production of target compounds using NADPH as reducing equivalent within their synthetic pathways.     

Nitidine chloride inhibited the expression of S phase kinase-associated protein 2 in ovarian cancer cells

Nitidine chloride (NC) has been reported to exert its anti-tumor activity in various types of human cancers. However, the molecular mechanism of NC-mediated tumor suppressive function is largely unclear. In the current study, we used several approaches such as MTT, FACS, RT-PCR, Western blotting analysis, invasion assay, transfection, to explore the molecular basis of NC-triggered anti-cancer activity. We found that NC inhibited cell growth, induced cell apoptosis, caused cell cycle arrest in ovarian cancer cells. Emerging evidence has demonstrated that Skp2 plays an important oncogenic role in ovarian cancer. Therefore, we also explored whether NC exerts its biologic function via downregulation of Skp2 in ovarian cancer cells. We observed that NC significantly inhibited the expression of Skp2 in ovarian cancer cells. Notably, overexpression of Skp2 abrogated the anti-cancer activity induced by NC in ovarian cancer cells. Consistently, downregulation of Skp2 expression enhanced the sensitivity of ovarian cancer cells to NC treatment. Thus, inactivation of Skp2 by NC could be a novel strategy for the treatment of human ovarian cancer.     

Short exposure to paclitaxel induces multipolar spindle formation and aneuploidy through promotion of acentrosomal pole assembly

Paclitaxel is a widely used microtubule drug and cancer medicine. Here we report that by short exposure to paclitaxel at a low dose, multipolar spindles were induced in mitotic cells without centrosome amplification. Both TPX2 depletion and Aurora-A overexpression antagonized the multipolarity. Live cell imaging showed that some paclitaxel-treated cells accomplished multipolar cell division and a portion of the daughter cells went on to the next round of mitosis. The surviving cells grew into clones with varied genome content. The results indicated that an aneuploidy population could be induced by short exposure to paclitaxel at a low dose, implicating potential side effects of paclitaxel.