Leymus chinensis (Trin.) Tzvel. is a perennial rhizome grass of the Poaceae (also called Gramineae) family, which adapts well to drought, saline and alkaline conditions. However, little is known about the stress tolerance of L. chinensis at the molecular level. microRNAs (miRNAs) are known to play critical roles in nutrient homeostasis, developmental processes, pathogen responses, and abiotic stress in plants. In this study, we used Solexa sequencing technology to generate high-quality small RNA data from three L. chinensis groups: a control group, a saline-alkaline stress group (100 mM NaCl and 200 mM NaHCO3), and a drought stress group (20% polyethylene glycol 2000). From these data we identified 132 known miRNAs and 16 novel miRNAs candidates. For these miRNAs we also identified target genes that encode a broad range of proteins that may be correlated with abiotic stress regulation. This is the first study to demonstrate differentially expressed miRNAs in L. chinensis under saline-alkali and drought stress. These findings may help explain the saline-alkaline and drought stress responses in L. chinensis.
More than 20 post-transcriptional gene silencing (PTGS) suppressors have been found since HC-Pro, the first gene silencing suppressor, was found in 1998. The silencing suppressor strongly suggested that gene silencing functions as natural defense mechanisms against viruses. It also represented a valuable tool for the dissection of the gene silencing pathway. We have used P1/HC-Pro RNA silencing suppressor activity to increase green fluorescent protein (GFP) expression in tobacco using an Agrobacterium-mediated transient expression system. P1/HC-Pro stimulated GFP-gene expression but not dsGFP-gene expression was shown by RT-PCR, Northern and Western blot analysis. Expression of the gene silencing suppressor and the target gene provided a new strategy of heterogeneous gene expressing in plants. It may be of commercial significance to produce foreign proteins using plant bioreactors.
An equivalent electrical network method is presented in this paper to analyze the cooling characteristics of a laser diode module (LDM). And a modified equivalent model of a thermoelectric cooler (TEC) with an adjunctive thermal resistance and a contact resistance is proposed. The performance of a commercial TEC has been simulated. The thermal analysis of a LDM incorporated with a TEC has been performed by using an equivalent circuit model of the LDM. In the analysis the change of LD current, TEC current,and the ambient temperature are all considered. It shows that the equivalent circuit approach is an effective tool for the qualitative analysis of TEC and LDM. Heat generation and dissipation in LD packages without TEC have been investigated both analytically and experimentally [14]. However, the thermal analysis of LDM incorporated with a TEC has not yet been sufficiently investigated. A finite element method to analyse a LDM has been presented in reference [5][6]. These works were only primary and the method suffers from a great limitation that its operation can not be modeled in CFD or ANSYS software directly since TEC's performance does not obey standard rules of conduction. In addition, the method is complex and all internal characteristics of the device have to be known.In this paper an equivalent electrical network method is presented to analyze the cooling and heating characteristics of a LDM. Following an approach similar to reference[7-1 and considered the adjunctive thermal resistance and the contact resistance, a modified equivalent model of a TEC is also presented. Then an equivalent circuit model of LDM incorporated with a TEC is developed in order to understand the thermal behavior of a LDM. The thermal analysis of a LDM is performed through the circuit model.A typical LDM is shown in Fig. 1. As an important part of the thermal management of optical package, a TEC is commonly used for cooling, heat pumping and maintaining the LI~s operating temperature. A negative temperature coefficient thermistor (NTC) mounted near the LD chip is used to monitor the chip temperature (not shown in Fig. 1). The NTC resistance decreases with increasing temperature. As the temperature inside the laser changes, the NTC resistance change is translated into the supply of current to the TEC.The exothermic heat of the LD is the Joule heat gen-* E-mail: mingwei_dlmu@ sina. com~ yangmingwei@ hit. edu. cn where Rm is the resistance of the LD. The internal heat convection and thermal radiation are ignored. A TEC relies on the Peltier effect and directly uses electrical energy for cooling and heating. A TEC consists of many arrays of positively-doped (p-type) and negatively doped (n-type) semiconductor pellets connected electrically in series and thermally in parallel between ceramic substrates. Each adjacent pair of p-type and n-type pellets is referred to as a thermocouple and there are N thermocouples in a TEC. A single-stage TEC is shown in Fig. 2 which only shows a single thermoeouple.Here, the controlled and uncontrolled...
BackgroundFor efficient and large scale production of recombinant proteins in plants transient expression by agroinfection has a number of advantages over stable transformation. Simple manipulation, rapid analysis and high expression efficiency are possible. In pea, Pisum sativum, a Virus Induced Gene Silencing System using the pea early browning virus has been converted into an efficient agroinfection system by converting the two RNA genomes of the virus into binary expression vectors for Agrobacterium transformation.ResultsBy vacuum infiltration (0.08 Mpa, 1 min) of germinating pea seeds with 2-3 cm roots with Agrobacteria carrying the binary vectors, expression of the gene for Green Fluorescent Protein as marker and the gene for the human acidic fibroblast growth factor (aFGF) was obtained in 80% of the infiltrated developing seedlings. Maximal production of the recombinant proteins was achieved 12-15 days after infiltration.ConclusionsCompared to the leaf injection method vacuum infiltration of germinated seeds is highly efficient allowing large scale production of plants transiently expressing recombinant proteins. The production cycle of plants for harvesting the recombinant protein was shortened from 30 days for leaf injection to 15 days by applying vacuum infiltration. The synthesized aFGF was purified by heparin-affinity chromatography and its mitogenic activity on NIH 3T3 cells confirmed to be similar to a commercial product.
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