Identification of genes induced by salt stress from Medicago truncatula L. seedlings

In order to identify genes induced during the salt stress response in barrel medic (Medicago truncatula L) seedlings, a cDNA library by salt stress was constructed  by suppression subtractive hybridization (SSH). Total RNA from 15-day-old seedlings was used as a ‘driver’, and total RNA from seedlings induced by salt was used as a ‘tester’. One hundred and sixty nine clones identified as positive clones by reverse northern dot-blotting resulted in 75 uni-ESTs that comprised of 13 contigs  and 62 singletons. Basic Local Alignment Search Tool (BLAST) analysis of deduced protein sequences revealed that 35 expressed sequence tags (ESTs) had identity similar to proteins with known function, while 27 could not be annotated at all. Most of the known function sequences were homologous to genes involved in abiotic stress in plants. Among these protein, citrate synthase, ribulose- 1,5-bisphosphate carboxylase, chloroplast protein, phosphoenolpyruvate carboxylase and  chloroplast outer envelope protein are related to photosynthesis; DNA binding/transcription factor, putative AP2/EREBP transcription factor, Cab9 gene, photosystem II polypeptide and calcium-dependent protein kinase play a significant role in signal transduction and transcription regulation; and aldolase and sucrose synthase are interrelated to osmolyte synthesis. Moreover, 5 of the ESTs, similar to genes from other plant species and closely involved in salt stress were isolated from M. truncatula L. They are superoxide dimutase (SOD)-1, gene for copper/zinc superoxide dismutase, cysteine protease, Na+/H+ antiporter and salt overly sensitive 2 (SOS2). To further assess the expression level of salt-induced ESTs, real-time polymerase chain reaction (PCR) analysis was employed, and the result showed that these genes have significantly increased expression and probably play an important role in the response of plants to salt stress.Key words: Barrel medic (Medicago truncatula L.), suppression subtraction hybridization (SSH), reverse northern dot-blotting, salt stress, real-time polymerase chain reaction (PCR)

Mitochondrial Genome of an 8,400-Year-Old Individual from Northern China Reveals a Novel Sub-Clade under C5d

Ancient DNA studies have always refreshed our understanding of the human past that can’t be tracked by modern DNA alone. Until recently, ancient mitochondrial genomic studies in East Asia are still very limited. Here, we retrieved the whole mitochondrial genome of an 8,400-year- old individual from Inner Mongolia, China. Phylogenetic analyses show that the individual belongs to a previously undescribed clade under haplogroup C5d that was most probably originated in northern Asia and may have a very low frequency in extant populations that is not yet sampled. We further characterized the demographic history of mitochondrial haplogroups C5 and C5d, and found that C5 experienced a sharp increase in population size starting from around 4,000 years before present (BP). The time when intensive millet farming was built by populations who are associated with the lower Xiajiadian culture and was widely adopted in northern China. We caution that people related to haplogroup C5 may added this farming technology to their original way of life and that the various subsistence may provide abundant food sources and may further contribute to the increase of the population size

MicroRNA Let-7a Inhibits Proliferation of Human Prostate Cancer Cells In Vitro and In Vivo by Targeting E2F2 and CCND2

Previous work has shown reduced expression levels of let-7 in lung tumors. But little is known about the expression or mechanisms of let-7a in prostate cancer. In this study, we used in vitro and in vivo approaches to investigate whether E2F2 and CCND2 are direct targets of let-7a, and if let-7a acts as a tumor suppressor in prostate cancer by down-regulating E2F2 and CCND2.Findings Real-time RT-PCR demonstrated that decreased levels of let-7a are present in resected prostate cancer samples and prostate cancer cell lines. Cellular proliferation was inhibited in PC3 cells and LNCaP cells after transfection with let-7a. Cell cycle analysis showed that let-7a induced cell cycle arrest at the G1/S phase. A dual-luciferase reporter assay demonstrated that the 3′UTR of E2F2 and CCND2 were directly bound to let-7a and western blotting analysis further indicated that let-7a down-regulated the expression of E2F2 and CCND2. Our xenograft models of prostate cancer confirmed the capability of let-7a to inhibit prostate tumor development in vivo.These findings help to unravel the anti-proliferative mechanisms of let-7a in prostate cancer. Let-7a may also be novel therapeutic candidate for prostate cancer given its ability to induce cell-cycle arrest and inhibit cell growth, especially in hormone-refractory prostate cancer

Isolation and functional characterization of a Medicago sativa L. gene, MsLEA3-1

A full-length cDNA of 1,728 nt, called MsLEA3-1, was cloned from alfalfa by rapid amplification of cDNA ends from an expressed sequence tag homologous to soybean pGmPM10 (accession No. AAA91965.1). MsLEA3-1, encodes a deduced protein of 436 amino acids, a calculated molecular weight of 47.0 kDa, a theoretical isoelectric point of 5.18, and closest homology with late embryogenesis abundant proteins in soybean. Sequence homology suggested a signal peptide in the N terminus, and subcellular localization with GFP revealed that MsLEA3-1 was localized preferentially to the nucleolus. The transcript titre of MsLEA3-1 was strongly enriched in leaves compared with roots and stems of mature alfalfa plants. Gene expression of MsLEA3-1 was strongly induced when seedlings were treated with NaCl and ABA. Expression of the MsLEA3-1 transgenic was detected in transgenic tobacco. Malondialdehyde content and, electrical conductivity content were reduced and electrical conductivity and proline content were increased in transgenic tobacco compared with non-transgenic tobacco under salt stress. The results showed that accumulation of the MsLEA3-1 protein in the vegetative tissues of transgenic plants enhanced their tolerance to salt stress. These results demonstrate a role for the MsLEA3-1 protein in stress protection and suggest the potential of the MsLEA3-1 gene for genetic engineering of salt tolerance

Arabidopsis NUCLEOSTEMIN-LIKE 1 (NSN1) regulates cell cycling potentially by cooperating with nucleosome assembly protein AtNAP1;1

Abstract Background In mammals, nucleostemin (NS), a nucleolar GTPase, is involved in stem cell proliferation, embryogenesis and ribosome biogenesis. Arabidopsis NUCLEOSTEMIN-LIKE 1 (NSN1) has previously been shown to be essential for plant growth and development. However, the role of NSN1 in cell proliferation is largely unknown. Results Using nsn1, a loss-of-function mutant of Arabidopsis NSN1, we investigated the function of NSN1 in plant cell proliferation and cell cycle regulation. Morphologically, nsn1 exhibited developmental defects in both leaves and roots, producing severely reduced vegetative organs with a much smaller number of cells than those in the wild type. Dynamic analysis of leaf and root growth revealed a lower cell proliferation rate and slower cell division in nsn1. Consistently, the transcriptional levels of key cell  cycle genes, including those regulating the transition of G1-S and G2-M, were reduced drastically in nsn1. The introduction of CYCLIN B1::GUS into nsn1 resulted in confined expression of GUS in both the leaf primordia and root meristem, indicating that cell proliferation was hampered by the mutation of NSN1. Upon subjection to treatment with bleomycin and methyl methanesulfonate (MMS), nsn1 plants exhibited hypersensitivity to the genotoxic agents. In the nucleus, NSN1 interacted with nucleosome assembly protein1 (AtNAP1;1), a highly conserved histone chaperone functioning in cell proliferation. Notably, the N-terminal conserved domains of Arabidopsis NSN1 were critical for the physical interaction. Conclusions As a conserved homolog of mammalian nucleostemin, Arabidopsis NSN1 plays pivotal roles in embryogenesis and ribosome biogenesis. In this study, NSN1 was found to function as a positive regulator in cell cycle progression. The interaction between NSN1 and histone chaperone AtNAP1;1, and the high resemblance in sensitivity to genotoxics between nsn1 and atnap1;1 imply the indispensability of the two nuclear proteins for cell cycle regulation. This work provides an insight into the delicate control of cell proliferation through the cooperation of a GTP-binding protein with a nucleosome assembly/disassembly protein in Arabidopsis

The III–V Triple-Junction Solar Cell Characteristics and Optimization with a Fresnel Lens Concentrator

At present, the Fresnel lens are commonly used as the condenser in high-concentrating photovoltaic (HCPV) modules. It is ideally believed that the output power of a III–V triple-junction solar cell which is placed on the focal plane of a Fresnel lens is the largest, because the intensity of the sunlight on the focal plane is the largest. Actually, according to our work, the dispersion of sunlight through a Fresnel lens and the nonparallelism and divergence of the incident light will lead to changes in the spectrum and the homogeneity of illumination, and cause a drop of the solar cell output. In this paper, the influence of the dispersion and nonparallel incidence of the light on the output of a triple-junction solar cell at different positions near the focal plane were theoretically studied, combined with the light-tracing simulation method and triple-junction solar cell circuit network model. The results show that the III–V triple-junction solar cell has the highest output power in both sides of the focal plane positions. The output power can be increased by about 15% after being optimized. The simulation results were verified by the experiments