The diurnal emission of floral scent in Oncidium hybrid orchid is controlled by CIRCADIAN CLOCK ASSOCIATED 1 (CCA1) through the direct regulation on terpene synthase.

BACKGROUND: To adapt the periodic fluctuation of environmental factors, plants are subtle to monitor the natural variation for the growth and development. The daily activities and physiological functions in coordination with the natural variation are regulated by circadian clock genes. The circadian emission of floral scents is one of the rhythmic physiological activities controlled by circadian clock genes. Here, we study the molecular mechanism of circadian emission pattern of ocimene and linalool compounds in Oncidium Sharry Baby (Onc. SB) orchid. RESULTS: GC-Mass analysis revealed that Onc. SB periodically emitted ocimene and linalool during 6 to 14 o'clock daily. Terpene synthase, one of the key gene in the terpenoid biosynthetic pathway is expressed in coordination with scent emission. The promoter structure of terpene synthase revealed a circadian binding sequence (CBS), 5'-AGATTTTT-3' for CIRCADIAN CLOCK ASSOCIATED1 (CCA1) transcription factor. EMSA data confirms the binding affinity of CCA1. Transactivation assay further verified that TPS expression is regulated by CCA1. It suggests that the emission of floral scents is controlled by CCA1. CONCLUSIONS: The work validates that the mechanism of circadian emission of floral scents in Onc. Sharry Baby is controlled by the oscillator gene, CCA1(CIRCADIAN CLOCK ASSOCIATED 1) under light condition. CCA1 transcription factor up-regulates terpene synthase (TPS) by binding on CBS motif, 5'-AGATTTTT-3' of promoter region to affect the circadian emission of floral scents in Onc. SB.

Advances of selectable marker genes in plastid genetic engineering.

Plastid genetic engineering is a safer, more precise, and more efficient transgene expression system than the nuclear genetic transformation system. It has been widely used in basic research and biotechnology applications as the next-generation transgenic technology in plants. Similar to nuclear genetic transformation, selection markers are needed in plastid genetic engineering to identify 'true' transformants and acquire homoplasmy. Because of the high copy number of plastids, maternal inheritance of the plastid genome, and the long process of homogenization of transplastomic plants, the selection markers for plastid genetic engineering are different from those used in the nuclear transformation system. At present, antibiotic resistance genes are the most commonly used selectable markers in the transplastomic selections. However for biosafety reasons, they needed to be replaced with either alternative markers or marker-free systems for the plastid genetic engineering. In this review, we have evaluated and summarized the positive and negative features of the selectable markers and marker elimination strategies commonly used in the plastid engineering research in the literature on plastid genetic engineering research. In addition, we have reviewed the features of the reporter genes used in plastid genetic engineering. We hope this review can help improving the current and developing new selectable markers and marker removal systems, and further promote the development of plastid genetic engineering, especially on the monocotyledonous plants.

[Screening of high-yield PUFAs Mortierella isabellina strain].

The original strain Mortierella isabellina As3.3410 was treated by microwave and ultraviolet. Mutated strains were screened by acetyl salicylic acid and low temperature (15°C). A high-yield strain named as A35-4 was successfully selected. The biomass of this strain was 17.9 g/L, oil content was 67.8%, oil production was 12.12 g/L, polyunsaturated fatty acids (PUFAs) content was 20.2%, and production of PUFAs was 2.46 g/L, which increased 32.6%, 49.8%, 98.69%, 14.0%, and 125.7% compared with the original A0 stain, respectively. The continuous slope transmission experiments confirmed that the strain had a good genetic stability. The study is beneficial for cloning high efficiency genes for PUFAs and producing PUFAs in this stain, and lays the ground work for creation of transgenic plants containing high levels of PUFAs.

Folate stimulates ERK1/2 phosphorylation and cell proliferation in fetal neural stem cells.

Cellular events for neural progenitor cells, such as proliferation and differentiation, are regulated by multiple intrinsic and extrinsic cell signals. Folate plays central roles in central nervous system development, so folate, as an extrinsic signal, may affect neural stem cell (NSC) proliferation and differentiation. In this study, we have investigated the effect of folate on extracellular signal-regulated kinase (ERK1/2) phosphorylation, cell proliferation and apoptosis in fetal NSCs. The results showed that treatment of neurospheres with folate increased ERK1/2 phosphorylation and cell proliferation in a concentration-dependent manner. Folate also decreased the percentage of apoptotic cells. All of these effects of folate were prevented by a selective inhibitor (U0126) of mitogen-activated/ERK kinase 1/2. In conclusion, fetal NSCs respond to folate with ERKl/2 phosphorylation, cell proliferation and decreased apoptosis. This mechanism may mediate the regulation by folate of neurogenesis in the central nervous system.

Folate deficiency induces neural stem cell apoptosis by increasing homocysteine in vitro.

Cellular events for neural progenitor cells, such as proliferation and differentiation, are regulated by multiple intrinsic and extrinsic cell signals. Folate plays a central role in central nervous system development, so folate, as an extrinsic signal, may affect neural stem cell (NSC) proliferation and differentiation. In the present study, we investigated the effects of folate deficiency on the cell proliferation, cell apoptosis and homocysteine concentrations in NSCs. NSCs were isolated from fetal rats and identified as NSCs by their expression of immunoreactive nestin. Cell proliferation was quantitated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Apoptotic cells were detected and confirmed by flow cytometric analysis. We measured homocysteine concentrations in NSCs by high performance liquid chromatography and detected the expression of caspase-3 by western blot method. Folate deficiency not only decreased cell proliferation, but also increased the apoptotic rate of NSCs as demonstrated by the increased expression of early apoptotic markers such as caspase-3, compared to control group (p<0.05). Furthermore, There was a statistically significant increase in homocysteine concentration during folate deficiency in NSCs (p<0.05). These data suggest that folate affects the cell proliferation, apoptosis and homocysteine generation in NSC cells.