Research progress on the source, production, and anti-cancer mechanisms of paclitaxel.

Paclitaxel, a tetracyclic diterpenoid compounds, was firstly isolated from the bark of the Pacific yew trees. Currently, as a low toxicity, high efficiency, and broad-spectrum natural anti-cancer drug, paclitaxel has been widely used against ovarian cancer, breast cancer, uterine cancer, and other cancers. As the matter of fact, natural paclitaxel from Taxus species has been proved to be environmentally unsustainable and economically unfeasible. For this reason, researchers from all over the world are devoted to searching for new ways of obtaining paclitaxel. At present, other methods, including artificial cultivation of Taxus plants, microbial fermentation, chemical synthesis, tissue and cell culture have been sought and developed subsequently. Meanwhile, the biosynthesis of paclitaxel is also an extremely attractive method. Unlike other anti-cancer drugs, paclitaxel has its unique anti-cancer mechanisms. Here, the source, production, and anti-cancer mechanisms of paclitaxel were summarized and reviewed, which can provide theoretical basis and reference for further research on the production, anti-cancer mechanisms and utilization of paclitaxel.

Long-chain acyl-CoA synthetase 2 is involved in seed oil production in Brassica napus.

BACKGROUND: Triacylglycerols (TAGs) are the main composition of plant seed oil. Long-chain acyl-coenzyme A synthetases (LACSs) catalyze the synthesis of long-chain acyl-coenzyme A, which is one of the primary substrates for TAG synthesis. In Arabidopsis, the LACS gene family contains nine members, among which LACS1 and LACS9 have overlapping functions in TAG biosynthesis. However, functional characterization of LACS proteins in rapeseed have been rarely reported. RESULTS: An orthologue of the Arabidopsis LACS2 gene (BnLACS2) that is highly expressed in developing seeds was identified in rapeseed (Brassica napus). The BnLACS2-GFP fusion protein was mainly localized to the endoplasmic reticulum, where TAG biosynthesis occurs. Interestingly, overexpression of the BnLACS2 gene resulted in significantly higher oil contents in transgenic rapeseed plants compared to wild type, while BnLACS2-RNAi transgenic rapeseed plants had decreased oil contents. Furthermore, quantitative real-time PCR expression data revealed that the expression of several genes involved in glycolysis, as well as fatty acid (FA) and lipid biosynthesis, was also affected in transgenic plants. CONCLUSIONS: A long chain acyl-CoA synthetase, BnLACS2, located in the endoplasmic reticulum was identified in B. napus. Overexpression of BnLACS2 in yeast and rapeseed could increase oil content, while BnLACS2-RNAi transgenic rapeseed plants exhibited decreased oil content. Furthermore, BnLACS2 transcription increased the expression of genes involved in glycolysis, and FA and lipid synthesis in developing seeds. These results suggested that BnLACS2 is an important factor for seed oil production in B. napus.

Candidate genes-association study to identify loci related to oleic acid in Brassica napus using SNP markers and their heterologous expression in yeast.

Brassica napus (rapeseed) serves as a main source of edible oil, and the oil's quality is mainly determined by the relative proportions of fatty acids. A high oleic acid concentration in B. napus oil increases its shelf life and oxidative stability. Therefore, attaining a high oleic acid concentration is necessary to enhance the nutritional quality of rapeseed oil. Here, an association study of candidate genes was conducted using a population of 324 genetically diverse rapeseed accessions, and several loci related to oleic acid content were identified. Furthermore, these loci were functionally characterized in Saccharomyces cerevisiae to assess their functions, and the promising candidate loci were validated using single nucleotide polymorphic markers in an independent inbred population. The results increased our understanding of fatty acid metabolism in B. napus. Moreover, these findings may assist in marker-based breeding efforts to improve the fatty acid composition and quality of B. napus oil.

Recent advances in enhancement of oil content in oilseed crops.

Plant oils are very valuable agricultural commodity. The manipulation of seed oil composition to deliver enhanced fatty acid compositions, which are appropriate for feed or fuel, has always been a main objective of metabolic engineers. The last two decennary have been noticeable by numerous significant events in genetic engineering for identification of different gene targets to improve oil yield in oilseed crops. Particularly, genetic engineering approaches have presented major breakthrough in elevating oil content in oilseed crops such as Brassica napus and soybean. Additionally, current research efforts to explore the possibilities to modify the genetic expression of key regulators of oil accumulation along with biochemical studies to elucidate lipid biosynthesis will establish protocols to develop transgenic oilseed crops along much improved oil content. In this review, we describe current distinct genetic engineering approaches investigated by researchers for ameliorating oil content and its nutritional quality. Moreover, we will also discuss some auspicious and innovative approaches and challenges for engineering oil content to yield oil at much higher rate in oilseed crops.

Improving seed germination and oil contents by regulating the GDSL transcriptional level in Brassica napus.

KEY MESSAGE: Seed germination rate and oil content can be regulated at theGDSL transcriptional level by eitherAtGDSL1 orBnGDSL1 inB. napus. Gly-Asp-Ser-Leu (GDSL)-motif lipases represent an important subfamily of lipolytic enzymes, which play important roles in lipid metabolism, seed development, abiotic stress, and pathogen defense. In the present study, two closely related GDSL-motif lipases, Brassica napus GDSL1 and Arabidopsis thaliana GDSL1, were characterized as functioning in regulating germination rate and seed oil content in B. napus. AtGDSL1 and BnGDSL1 overexpression lines showed an increased seed germination rate and improved seedling establishment compared with wild type. Meanwhile, the constitutive overexpression of AtGDSL1 and BnGDSL1 promoted lipid catabolism and decreased the seed oil content. While RNAi-mediated suppression of BnGDSL1 (Bngdsl1) in B. napus improved the seed oil content and decreased seed germination rate. Moreover, the Bngdsl1 transgenic seeds showed changes in the fatty acid (FA) composition, featuring an increase in C18:1 and a decrease in C18:2 and C18:3. The transcriptional levels of six related core enzymes involved in FA mobilization were all elevated in the AtGDSL1 and BnGDSL1 overexpression lines, but strongly suppressed in the Bngdsl1 transgenic line. These results suggest that improving the seed germination and seed oil content in B. napus could be achieved by regulating the GDSL transcriptional level.

[Protective effect of succinic acid on cerebellar Purkinje cells of neonatal rats with convulsion].

OBJECTIVE: To investigate the protective effect of succinic acid (SA) on the cerebellar Purkinje cells (PCs) of neonatal rats with convulsion. METHODS: A total of 120 healthy neonatal Sprague-Dawley rats aged 7 days were randomly divided into a neonatal period group and a developmental period group. Each of the two groups were further divided into 6 sub-groups: normal control, convulsion model, low-dose phenobarbital (PB) (30 mg/kg), high-dose PB (120 mg/kg), low-dose SA (30 mg/kg), and high-dose SA (120 mg/kg). Intraperitoneal injection of pentylenetetrazole was performed to establish the convulsion model. The normal control group was treated with normal saline instead. The rats in the neonatal group were sacrificed at 30 minutes after the injection of PB, SA, or normal saline, and the cerebellum was obtained. Those in the developmental group were sacrificed 30 days after the injection of PB, SA, or normal saline, and the cerebellum was obtained. Whole cell patch clamp technique was used to record the action potential (AP) of PCs in the cerebellar slices of neonatal rats; the parallel fibers (PF) were stimulated at a low frequency to induce excitatory postsynaptic current (EPSC). The effect of SA on long-term depression (LTD) of PCs was observed. RESULTS: Compared with the normal control groups, the neonatal and developmental rats with convulsion had a significantly higher AP frequency of PCs (P<0.05), and the developmental rats with convulsion had a significantly decreased threshold stimulus (P<0.01) and a significantly greater inhibition of the amplitude of EPSC in PCs (P<0.05). Compared with the normal control groups, the neonatal and developmental rats with convulsion in the high-dose PB groups had a significantly decreased threshold stimulus (P<0.01), a significantly higher AP frequency of PCs (P<0.05), and a significantly greater inhibition of EPSC in PCs (P<0.05). Compared with the neonatal and developmental rats in the convulsion model groups, those in the high-dose SA groups had a significantly decreased AP frequency of PCs (P<0.05). The developmental rats in the low- and high-dose SA groups had a significantly higher AP threshold than those in the convulsion model group (P<0.05). CONCLUSIONS: The high excitability of PCs and the abnormal PF-PC synaptic plasticity caused by convulsion in neonatal rats may last to the developmental period, which can be aggravated by PB, while SA can reduce the excitability of PCs in neonatal rats with convulsion and repair the short- and long-term abnormalities of LTD of PCs caused by convulsion.

[Effect of Flos Daturae Alkaloids on TGF-beta1-induced Epithelial-Mesenchymal Transition of Human Pulmonary Adenocarcinoma A549 Cells].

OBJECTIVE: To study the effect of Flos Daturae alkaloids (FDA) on TGF-beta1-1uuuu;U epithelial-mesenchymal transition (EMT) of human pulmonary adenocarcinoma A549 cells. METHODS: A549 cells in vitro cultured were randomly divided into 5 groups, i.e., the blank control group, the TGF-beta1 group, the low dose FDA group, the medium dose FDA group, and the high dose FDA group. The morphologies of A549 cells were observed. Expressions of cytokeratin (CK)-19 and alpha-smooth muscle actin (alpha-SMA) were detected by Western blot and real-time PCR at 24, 48, and 72 h, respectively. RESULTS: A549 cells in the TGF-beta1, group turned from cobblestone to spindle shape gradually. Those in low, medium and high dose FDA groups showed similar shapes to those of the TGF-beta1 group. There was no statistical difference in the morphology of A549 cells among the 3 dose FDA groups (P > 0.05). Western blot showed that, when compared with the blank control group, the expression of CK-19 was down-regulated, but the expression of alpha-SMA was up-regulated in the TGF-beta1 group (P < 0.01). Compared with the TGF-beta1, group, the expression of CK-19 was up-regulated, but the expression of alpha-SMA was suppressed in low, medium and high dose FDA groups (P < 0.01). The CK-19 expression obviously increased, but the alpha-SMA expression was suppressed in high dose FDA group at 72 h (P < 0.01). Real-time PCR results showed, as compared with the TGF-beta1 group, the mRNA expression of CK-19 was increased, but the mRNA expression of alpha-SMA was reduced in low, medium and high dose FDA groups (P < 0.01). CONCLUSIONS: FDA had no effect on EMT morphological changes of TGF-beta1 induced A549 cells. FDA could reverse characteristic markers of A549 cells during EMT to some extent, such as expressions of CK-19 and alpha-SMA. The expression of CK-19 (as the epithelium marker) increased and the expression of alpha-SMA (as the mesenchymal marker) was reduced. Besides, they were most obviously seen in the high dose FDA group at 72 h in a dose- and time-dependent manner.