Peanut (Arachis hypogaea L.) S-adenosylmethionine decarboxylase confers transgenic tobacco with elevated tolerance to salt stress.

Polyamines play an important role in stress response. In the pathway of polyamines synthesis, S-adenosylmethionine decarboxylase (SAMDC) is one of the key enzymes. In this study, a full length cDNA of SAMDC (AhSAMDC) was isolated from peanut (Arachis hypogaea L.). Phylogenetic analysis revealed high sequence similarity between AhSAMDC and SAMDC from other plants. In peanut seedlings exposed to sodium chloride (NaCl), the transcript level of AhSAMDC in roots was the highest at 24 h that decreased sharply at 72 and 96 h after 150 mM NaCl treatment. However, the expression of AhSAMDC in peanut leaves was significantly inhibited, and the transcript levels in leaves were not different compared with control These results implied the tissue-specific and time-specific expression of AhSAMDC. The physiological effects and functional mechanism of AhSAMDC were further evaluated by overexpressing AhSAMDC in tobaccos. The transgenic tobacco lines exhibited higher germination rate and longer root length under salt stress. Reduced membrane damage, higher antioxidant enzyme activity, and higher proline content were also observed in the transgenic tobacco seedlings. What's more, AhSAMDC also led to higher contents of spermidine and spermine, which can help to scavenge reactive oxygen species. Together, this study suggests that AhSAMDC enhances plant resistance to salt stress by improving polyamine content and alleviating membrane damage.

[Experimental study of toluidine blue-dextran-40 as lymphatic tracer in head and neck region].

Objective: To investigate the feasibility and application value of toluidine bule-dextran-40 (TB-Dex-40) as the tracer for lymphatic system in head and neck region. Methods: Twenty healthy adult New Zealand white rabbits were equally divided into two groups: the experimental group (TB-Dex-40 group, n=10) and the control group (TB group, n=10). Rabbits in experimental group received submucosal injection of 1.0% (0.14 mOsm/L) TB-Dex-40, and the control group received injection of 1.0% (32.60 mOsm/L) TB.The staining time and fading time of lymphatic vessels and lymphnodes in the neck region were recorded, and the diffusion ranges of the two dyes in the tongue region were measured. Lymph nodespecimen were collected for pathological examination after 10 min, 1 hour and 4 weeks of staining. The experimental animals were sacrificed before and 4 weeks after the experiment. After death, organs of heart, lung, liver and kidney were examined pathologically. Results: TB-Dex-40 reached sentinel lymph node (SLN) and stained lymphatic vessels at an average of (21.67±0.19) s after injection, while in control group was(3.22±0.34) s (P<0.01). The time difference between the two dyes reaching sentinel lymph nodes was statistically significant.The durations from lymphatic staining to marked fading were (19.70±1.34) min in experimental group and (14.30±0.95) min in control group, respectively.The difference was statistically significant (P<0.01). SLN staining by TB-Dex-40 was still evident after 4 weeks, while TB staining has completely faded after 2 d.The average ranges of diffusionin tongue were (10.50±1.08) mm in experimental group and (20.00±1.05) mm in controlgroup, respectively. The difference was statistically significant (P<0.01).No abnormalities were found in blood test and pathological examination of main organs. Conclusions: TB-Dex-40 has high specificity forstaining lymphatic vessels and is a good tracer with potential clinical value.

Cloning and characterization of SPL-family genes in the peanut (Arachis hypogaea L.).

SQUAMOSA promoter-binding protein-like (SPL) proteins play crucial roles in plant growth, development, and responses to environmental stressors. The peanut (Arachis hypogaea L.) is a globally important oil crop. In this study, we cloned the full-length cDNA of 15 SPLs in the peanut by transcriptome sequencing and rapid amplification of cDNA ends, and analyzed their genomic DNA sequences. cDNA lengths varied significantly, from 369 to 3102 bp. The SBP domain of the peanut SPL proteins was highly conserved compared to SPLs in other plant species. Based on their sequence similarity to SPLs from other plant species, the peanut SPLs could be grouped into five subgroups. In each subgroup, lengths of individual genes, conserved motif numbers, and distribution patterns were similar. Seven of the SPLs were predicted to be targets of miR156. The SPLs were ubiquitously expressed in the roots, leaves, flowers, gynophores, and seeds, with different expression levels and accumulation patterns. Significant differences in the expression of most of the SPLs were observed between juvenile and adult leaves, suggesting that they are involved in developmental regulation. Dynamic changes occurred in transcript levels at stage 1 (aerial grown green gynophores), stage 2 (gynophores buried in soil for about three days), and stage 3 (gynophores buried in soil for about nine days with enlarged pods). Possible roles that these genes play in peanut pod initiation are discussed.

Over-expression of the Arabidopsis CBF1 gene improves resistance of tomato leaves to low temperature under low irradiance.

A known Arabidopsis cDNA clone, the CRT/DRE binding factor 1 (CBF1), was isolated and introduced into tomato plants. CBF1 is a member of the CBF gene family related to low temperature and enhanced low temperature tolerance in plants. In the present work, transcripts of CBF1 could be detected in transgenic tomato leaves, and the photochemical efficiency of PSII (F(v) /F(m)) and oxidisable P700 in the transgenic tomato over-expressing CBF1 were higher than in non-transformed plants under low temperature stress at low irradiance. Similarly, higher activity of superoxide dismutase (SOD), higher non-photochemical quenching (NPQ), and lower malondialdehyde (MDA) content were also detected in transgenic tomato leaves. These results suggest that CBF1 protein plays an important role in protection of PSII and PSI during low temperature stress at low irradiance.

The challenge of developing green tea polyphenols as therapeutic agents.

The health benefits of green tea and its main constituent (-)-epigallocatechin gallate [(-)-EGCG] have been widely supported by results from epidemiological, cell culture, animal and clinical studies. On the other hand, there are a number of issues, such as stability, bioavailability and metabolic transformations under physiological conditions, facing the development of green tea polyphenols into therapeutic agents. We previously reported that the synthetic peracetate of (-)-EGCG has improved stability and better bioavailability than (-)-EGCG itself and can act as pro-drug under both in vitro and in vivo conditions. Analogs of catechins have been synthesized and their structure activity relationship provides an understanding to the mechanism of proteasome inhibition. Metabolic methylation of catechins leading to methylated (-)-EGCG may alter the biological activities of these compounds.

Green tea polyphenols as a natural tumour cell proteasome inhibitor.

The cancer-preventive effects of green tea and its main constituent (-)-epigallocatechin gallate [(-)-EGCG] are widely supported by results from epidemiological, cell culture, animal and clinical studies although the molecular target has not been well defined. We previously reported that ester bond-containing tea polyphenols, e. g. (-)-EGCG, and their synthetic analogs potently and specifically inhibited the proteasomal activity. Subsequently, we further demonstrated that methylation on green tea polyphenols under physiological conditions decreased their proteasome-inhibitory activity, contributing to decreased cancer-preventive effects of tea consumption. Since (-)-EGCG is unstable under physiological conditions, we also developed the peracetate-protected or prodrug form of (-)-EGCG, Pro-EGCG (1), and shown that Pro-EGCG (1) increases the bioavailability, stability, and proteasome-inhibitory and anticancer activities of (-)-EGCG in human breast cancer cells and xenografts, suggesting its potential use for cancer prevention and treatment.

Tea polyphenols, their biological effects and potential molecular targets.

Tea is the most popular beverage in the world, second only to water. Tea contains an infusion of the leaves from the Camellia sinensis plant rich in polyphenolic compounds known as catechins, the most abundant of which is (-)-EGCG. Although tea has been consumed for centuries, it has only recently been studied extensively as a health-promoting beverage that may act to prevent a number of chronic diseases and cancers. The results of several investigations indicate that green tea consumption may be of modest benefit in reducing the plasma concentration of cholesterol and preventing atherosclerosis. Additionally, the cancer-preventive effects of green tea are widely supported by results from epidemiological, cell culture, animal and clinical studies. In vitro cell culture studies show that tea polyphenols potently induce apoptotic cell death and cell cycle arrest in tumor cells but not in their normal cell counterparts. Green tea polyphenols were shown to affect several biological pathways, including growth factor-mediated pathway, the mitogen-activated protein (MAP) kinase-dependent pathway, and ubiquitin/proteasome degradation pathways. Various animal studies have revealed that treatment with green tea inhibits tumor incidence and multiplicity in different organ sites such as skin, lung, liver, stomach, mammary gland and colon. Recently, phase I and II clinical trials have been conducted to explore the anticancer effects of green tea in humans. A major challenge of cancer prevention is to integrate new molecular findings into clinical practice. Therefore, identification of more molecular targets and biomarkers for tea polyphenols is essential for improving the design of green tea trials and will greatly assist in a better understanding of the mechanisms underlying its anti-cancer activity.

[Three dimensional quantitative structure-activity relationship of farnesyl protein transferase inhibitors].

AIM: To build a three dimensional structure model that correlates the biological activities and the structures of a series of farnesyl protein transferase (FPT) inhibitors exemplified by the compound of 2, 3,4,5-tetrahydro-1-(1H-imidazol-4-ylmethyl)-4-(2-biphenylylcarbonyl)-1H-1, 4-benzodiazepine. METHODS AND RESULTS: Thirty-two FPT inhibitors with two types of scaffold were analyzed. Active conformations of which were studied using system search, a 3D-QSAR model were constructed using the method of comparative molecular field analysis (CoMFA). The resulting of cross-validated RCV2 = 0.602, non-cross-validated R2 = 0.958, SE = 0.270 and F = 124.5 indicate that the 3D-model possesses an ability to predict activities of new inhibitors. CONCLUSION: The information of CoMFA model offers an approach to designing new FPT inhibitors.