| As one of the essential macro-elements for plant growth and development, phosphorus affects almost all physiological reactions in plant. Phosphates are mainly obtained from soil by roots. However, currently lack of phosphate in soil has been a common problem wordwide. In China, 2/3 of the 107 million hectares of farmlands are in severe lack of phosphate, which has been the restrictive element for crop production. To make the soil more suitable for crop growth and high yield, agricultural scientists used more and more phosphate fertilizer, which leads to exhaustion of phosphate resources. Whats more, due to the bad utilization of phosphate, more and more phosphate are accumulated in soil and caused contamination. Improvement of phosphate utilization rate can be achieved by rational fertilizing, as well as genetic breeding to generate strains which have better utilization of soil phosphate. The latter one has been paid more attention and showed enormous latent force in application.Salt cress (Thellungiella salsuginea) belongs to the crucifer family (Brassicaceae). Its life cycle (2-5 months) , plant size, morphological and developmental traits are similar to Arabidopsis thaliana. As the first higher plant whose whole genome sequence has been determined, Arabidopsis thaliana is taken as the model organism of salt tolerance research in lab, although it is a typical glycophyte and not resistant to salt. Differently, T.salsuginea is highly resistant to stress conditions such as cold, drought and high salt, so it is more preferential to act as a model organism.In this work, we intend to research how T.salsuginea adapted to low-phosphate condition morphologically. To meet the need of growth and development in lack of phosphate, plants developed a series of mechanisms to utilize phosphate effectively during their evolution, including: morphological changes in root system, root figures and mass distribution in root caps; secretion of organic acids of low-molecular-mass, acidic phosphatase, the effect of mycorrhizae, dynamic changes in root absorbance, enhancement of phosphorus internal circulation and inductive expression of low-phosphate-related genes. In our work, we used wild type T. salsuginea (ecotype Shandong ). as experimental materials, and wild type of Arabidopsis thaliana was taken as control. Sterilized seed were sowe on 1/2 MS0 media with different concentrations of phosphate and cultured vertically under tissue cultural environment. The survival period was taken down and the changes in main roots and root hairs were observed. The phosphate concentrations used in the experiment were 0mM and 1.5 mM, respectively, and the mophorlogical differences were observed. Data show that the growth of main roots of Arabidopsis thaliana under 0 mM of phosphate was obviously suppressed and almost no growth was observed, moreover the leaves began to turn yellow until death. In comparison, the growth of main roots of T.salsuginea was suppressed to less extent, but leaves turned yellow slightly faster. T. salsuginea survived longer than Arabidopsis thaliana under 0 mM phosphate. In conclusion, these results indicate that T.salsuginea is more resistant to low-phosphate stress than Arabidopsis thaliana .To further confirm the reliability of results mentioned above, we cloned several low-phosphate-related genes such as AT4, IPS1, ACP5, MGD3, PAP1, SQD1 and PT1/2, and analysed their variation in expression levels in both T.salsuginea and Arabidopsis thaliana. The Total RNAs were extracted from T.salsuginea and Arabidopsis thaliana treated with 0 mM and 1.5 mM phosphate, respectively, and cDNA was obtained by reverse transcription. Specific primers and degenerate primers were designed and parts of these genes have been cloned by RT-PCR. Sequencing has been accomplished and Real-time PCR and Northern Blotting are in processing.
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