Homeotic transformation from stamen to petal in Lilium is associated with MADS-box genes and hormone signal transduction

Plant Growth Regulation - As one of the most popular bulbous plant with high ornamental value, Lilium spp. has been used as cut flower or green plants in urban landscapes and home gardening. We...     

Tn5 transposase-assisted transformation of indica rice

Here, we describe experiments on Tn5 transposase-assisted transformation of indica rice. Transposomes were formed in vitro as a result of hyperactive Tn5 transposase complexing with a transposon that contained a 19-bp tetracycline operator (tetO) sequence. To form modified projectiles for transformation, the Tn10-derived prokaryotic tetracycline repressor (TetR) proteins, which can bind transposomes via the high affinity of TetR for tetO, were immobilized onto the surface of bare gold microscopic particles. These projectiles were introduced into cells of the indica rice cultivar Zhuxian B by particle bombardment. Once projectiles were inside the cell, tetracycline induced an allosteric conformational change in TetR that resulted in the dissociation of TetR from tetO, and thus generated free transposomes. Molecular evidence of transposition was obtained by the cloning of insertion sites from many transgenic plants. We also demonstrated that the introduced foreign DNA was inherited stably over several generations. This technique is a promising transformation method for other plant species as it is species independent.     

Alterations in microRNA expression linked to microcystin-LR-induced tumorigenicity in human WRL-68 Cells

Microcystin-LR (MC-LR) is a cyclic heptapeptide that acts as a potent hepatotoxin and carcinogen. However, the mechanism of its carcinogenic action remains undetermined. In this study, MC-LR was used to induce the malignant transformation of the WRL-68 cell line. Alterations in microRNA (miRNA) expression in the transformed cell were analyzed to determine the role of miRNAs in MC-LR-induced carcinogenesis. Cultured WRL-68 cells (labeled 25MC10) were continuously exposed to a low concentration (10 μg/L) of MC-LR for 25 passages. Compared with the mock-treated parental cells, the induced 25MC10 cells exhibited a higher growth rate, resistance to serum-induced terminal differentiation, and tumorigenicity in a nude mouse xenograft test. A pilot miRNA expression array analysis was conducted on the 25MC10 cells, followed by validation of select miRNAs by RT-PCR. We found that the onco-miRNAs miR-21 and miR-221 displayed upregulated expression while the liver-specific miR-122 was downregulated. These results suggest that chronic MC-LR exposure alters the miRNA expression profile of WRL-68 cells and causes phenotypic transformation. We propose that characteristic miRNA alterations could be used as molecular targets for the development of environmental water monitoring methods.     

Solid state fermentation of aquatic macrophytes for crude protein extraction

Aquatic macrophytes such as Elodea nuttalli, Vallisneria natans, Alterranthera philoxerides that are widely distributed in water environments of Lake Taihu basin were used as substrate of solid state fermentation to produce crude protein extraction. The effects of single-strain fermentation and mixed strains fermentation of aquatic macrophytes on the production of crude protein extraction and cellulase activity are analyzed, respectively. The experimental results showed that the crude protein content of products with mixed strains fermentation is higher than that with single-strain fermentation. The crude protein content of V. natans fermented by Aspergillus niger and Candida utilis is the highest among the aquatic macrophytes examined in this study. V. natans is used as the substrate to be fermented by C. utilis and A. niger; their ratio is 1:1 at 28 ± 1 °C for 72 h. The crude protein of fermented V. natans is as high as 49.54%, with 128.82% of its increase rate. The cellulose activity reaches a maximum of 4.21 μ/ml at 84 h of fementation of V. natans. Thus, the solid state fermentation of aquatic macrophytes to produce crude protein extraction is promising, which make aquatic macrophytes a potential resource and thus is beneficial to the long-term ecological restoration of eutrophic lakes.     

Intracellular phosphorus metabolism of Microcystis aeruginosa under various redox potential in darkness

Phosphorus metabolism of Microcystis aeruginosa was studied under gradient redox potential from 252 mV to –70 mV in darkness. The release of phosphorus occurred in all the treatments, and this process was accelerated in darkness when the redox potential was lowered. Low redox potential in darkness stimulated the accumulation of polyphosphate (PolyP) and the degradation of polyglucose. The synthesis of PolyP delayed the decrease of intracellular orthophosphate. The death of M. aeruginosa was slowered when the redox potential was low in darkness. The accumulation of PolyP under low redox potential in the dark was very important to M. aeruginosa for endurance through the unfavorable growth conditions for maintaining phosphorus concentration, energy storage, and other physiological functions. The ability to accumulate PolyP in the dark and negative redox potential may be of considerable advantage in the low-light, organically rich, and low-redox habitats.     

Trophic status determines the nirS-denitrifier community in shallow freshwater lakes

To explore whether trophic status is involved in identifying the denitrifier communities in shallow freshwater lakes, comparative studies regarding the variation of nirS-denitrifier communities were performed in water columns of six shallow freshwater lakes, ranging from mesotrophic to hypereutrophic status, in Jiangsu province of China. Restriction fragment length polymorphism (RFLP) analysis and cloning, followed by sequence analysis of selected samples were performed to examine the nirS-denitrifier communities. Results showed that a same predominant nirS unique operational taxonomic unit (OTU) appeared in mesotrophic, light eutrophic and middle eutrophic lakes, while a different nirS OTU appeared in the hypereutrophic lake. The nirS dendrogram could be divided into four clusters, and suggested a habitat-specific observation. The nirS libraries from lakes having mesotrophic and light eutrophic statuses grouped together, while those from lakes having middle eutrophic and hypereutrophic statuses diverged. The hypereutrophic lake had the lowest richness and evenness of nirS. Thus, the observed variation of nirS distribution and diversity was mainly affected by the trophic status, via some environmental factors such as pH, dissolved oxygen, nitrite, nitrate and chlorophyll-a concentrations.     

An improved particle bombardment for the generation of transgenic plants by direct immobilization of relleasable Tn5 transposases onto gold particles

We have developed a modified particle bombardment method for plant transgenesis. An intein-tag and a 6×Cys-tag were successively fused to the N-terminus of a hyperactive Tn5 transposase. The modified transposase was immobilized on bare gold microscopic particles via covalent binding of a 6×Cys-tag sulfydryl groups to the gold surface. The tethered transposase can bind the transposon DNA in vitro to form the transposome in the absence of Mg2? ions. After bombardment of the gold particles carrying the transposomes into the plant cells, the transposomes will be released from the carrier due to the activated self-cleavage function of intein-tag. Our data showed this procedure integrated foreign DNA into the plant genome with an increased transformation frequency as compared to the conventional particle bombardment method. A single copy insertion can also be obtained by decreasing of the assembled transposon DNA amount in relation to plant cell biomass.     

Vertical distribution of bacterial community structure in the sediments of two eutrophic lakes revealed by denaturing gradient gel electrophoresis (DGGE) and multivariate analysis techniques

Vertical distribution of bacterial community structure was investigated in the sediments of two eutrophic lakes of China, Lake Taihu and Lake Xuanwu. Profiles of bacterial communities were generated using a molecular fingerprinting technique, denaturing gradient gel electrophoresis (DGGE) followed by DNA sequence analysis, and the results were interpreted with multivariate statistical analysis. To assess changes in the genetic diversity of bacterial communities with changing depth, DGGE banding patterns were analysed by cluster analysis. Distinct clusters were recognized in different sampling stations of Lake Taihu. Canonical correspondence analysis (CCA) was carried out to infer the relationship between environmental variables and bacterial community structure. DGGE samples collected at the same sampling site clustered together in both lakes. Total phosphorus, organic matter and pH were considered to be the key factors driving the changes in bacterial community composition.