Halophila (thellungiella Halophila) Thgpx2, And Thgpx6 Gene Cloning And Function Of A Preliminary Study

Salt stress is one of the most important abiotic stresses which affects the growth and yield of many crops.With the expansion of population,development of economy and the variation of climate condictions,water resource shortage and soil salinization are getting worse and worse.It is known that 20%ploughable land and 40%irrigated land of the world is subjected to various degrees soil salinization impacts.China owned more than 300 million hectares salinized land,which accounted for about 25% of our country's arable land.Soil Salinization,which severely affects agricultural production,has become one of the most important serious environment factors affecting the development of social economy.For a long time,the study on the improvement and usage of salinization land is extensively carried out.Since entirely different signal transduction pathway and regulation mechanisms may exist between halophytes and non-halophytes on the evolution,by means of genetic engineering technology,scientists isolated and cloned key genes related to salt-tolerant from Halophytes,cultivating genetically modified salt-tolerant plants,exploreing and using saline land to improve the current state of the environment with the the utilization of biological factors.Studies on Halophytes salt-related genes not only can help you know the salt-tolerant mechanism,but also lay a foundation for development of halophytes salt-tolerant resources and the cultivation of salt-tolerant crop varieties.At present,carrying out research on Halophytes salt-tolerant gene has gradually become an international hot spot on the salt-resisting field.High-salt,low temperature,drought and other adverse environment can cause the antioxidant response of plant easily.Oxidative stress can induce the generation of a range of defense enzymes,which include super oxide dismutase(SOD),ascorbate peroxidase(APX),catalase(CAT) and glutathione peroxidase(GPX).They play different roles in the process of scavenging reactive oxygen species(ROS).GPX is the primary enzyme to scaveng the oxygen free radicals in animals.In recent years, studies have shown that the plants have the same GPX family as the animals,and the functional research have been carried out.Salt cress(Thellungiella halophila) which has close relationship with Arabidopsis thaliana is cruciferous plant,can achieve life cycle under the stress of 300mM NaCl.It is an real salt-tolerant plants with 500mM NaCl.As a model of salt-tolerant plants,it will be very important to clarify the mechanism under the salt stress and clone the coding sequence of glutathione peroxidase which can scavenging ROS.According to the highly homologous with A.thaliana,we designed a pair of degenerate primers and cloned a gene named ThGPX2 by means of RACE-PCR technology.Based on EST and RACE-PCR technology,we obtained a gene named ThGPX6.Both of them were coding glutathione peroxidase.An analysis was made on the two gene sequences and their expression patterns under salt stress were studied as well.The results showed that the length of ThGPX2 was 740bp,Registration No. FJ357243,through open reading frame and homology comparison analysis,the ORF was 510bp,encoding 170 amino acids residues with calculated weight of 19020.62 Da and the pI 5.48,and there was conservative domains of GPX family in ThGPX2, Registration No.FJ357244,which confirmed that ThGPX2 belonged to the glutathione peroxidase family.The length of ThGPX6 was 892bp,the ORF was 702bp,encoding 234 amino acids residues with calculated weight of 25937.68 Da and the pI 9.35, there was also GPX family conservative domains and PHGPX characteristic domain, which confirmed that ThGPX6 belonged to PHGPX.The Semi-quantitative RT-PCR study showed that,under the salt stress for 12h, ThGPX2 expression abundance in leave and root was firstly increased and then declined with the increasement of salt concentration,the expression abundance in leave reached the peak when the salt concentration was 300mM,while in root it was 200mM.ThGPX6 expression abundance trend in leave and root exist differece.The expression abundance in leave increased as the increasement of salt concentration, while in root it took on firstly increased and then declined.The expression abundance in root reached the peak when the salt concentration was 300mM.The two genes expression abundance in leave and root was higher than that in CK,the expression abundance and the intensity of salt concentration were a positive correlation in a certain degree.Therefore,ThGPX2 and ThGPX6 were induced expression genes in T. halophila.