Cloning And Differential Gene Expression Of TsTRX In The Lungiella SalsugeInea In Response To Salt Stress

Oxidative stress ,an common secondly stress occurring after many kind of biotic or abiotic stresses such as salt stress, drought,heavy metal, radiation,low temperature ,microbic infection ,can change the plant internal redox environment and subsequently disturb its growth processes, metablism and existence. The stability of plant internal redox environment and plant tolerance to stresses are closely related with a more efficient antioxidant and redox regulatatory system.So, it is helpful for us to study the response mechanism of oxidative stress in order to understand the mechanism of stress response of plant.Thioredoxins, an ubiquitous small proteins with a redox active disulfide bridge in its conserved motif -CP(G)PC-,are universally distributed in eucaryote and procaryote and have a molecular mass of approximately 12Kda.By its disulfide/dithiol interchange reaction ,this protein can transmit the regulatory signals to seleted targets (enzymes, transcription factors etc ) and plays an important role in many plant physiological processes that includes photosynthesis, DNA synthesis, transcription, protein disulfide reduction , protein repair, filamentous phage assembly, cell apoptosis and seeds germinating and so on.Depending on cellular location and function of thioredoxins, There are two thioredoxin systems in high plants, One is NADP/thioredoxin system mainly existing in chloroplast of high plant and eucaryote algae and oxygenic photosynthetic prokaryote, which is composed of NADPH, NADPH-dependent thioredoxin reductase, thioredoxin-f and thioredoxin-m. The other is ferredoxin/thioredoxin system located in nonphotosynthetic tissue and cytosol of photosynthetic cell, which includes ferredoxin, ferredoxin dependent thioredoxin reductase,thioredoxin h. This two system constitutes important cellular redox regulatory system and can regulate theredox intercellular environment , metablism and signaling transduction.We have identified a nucleotide sequence from ESTs (expressed sepuence tagged)acquired fromZap-cDNA library of Thellungiella salsuginea treated with 200mmol.L-1 NaCl and analyzed its nucleotide sequence characterization, gene organization, and differential expression under salt stress. The total sequence is 663 basepairs with an open reading frame of 354 nucleotides encoding a novel h-type thioredoxin and an UTR of 37 basepairs at its 5 ' end and an UTR of 279 basepairs at its 3 ' end. The predicted amino acid sepuence of TsTRX is high similar to that of the other plant TsTRX. There is only one copy in Thellungiella salsuginea genome according to Southern blotting. Analysis of mRNA levels by Northern blotting indicated that the expression of TsTRX-h in Thellungiella salsuginea leaves was difference after being treated with 200 mmol.L-1NaCl for different hours and with different concentration of NaCl for the same time. The expression of TsTRX from different tissue also shows different. These results show that this gene is a stress response gene or plays an important role in slat stress tolerance. Aiming to identify the functions of this gene and do some further study, We have cloned the gene into the Agrobacterium tumefaciens binary vector PROK II and pCAMBIA 3013.