The Preliminary Study Of Physcomitrella Patens Response To Low Phosphorus Stress And PpMPS1 Function

Phosphorus is an essential macronutrient for the plant. It serves a variety of basic biological functions as a structural element of many molecules, such as nucleic acids and phospholipids, and plays a important role in energy metabolism, signal transduction, and regulation of enzymes. However, because of low mobility, phosphate is the most dilute among the major nutrients required for plants in soil. Plants absorb P as orthophosphate (inorganic phosphate). As a consequence, plants have evolved a series of morphological, physiological, biochemical, and molecular adaptations leading to increased survival ability under phosphate deficiency.Physcomitrella patens is a relatively lower plant. The adaptive response to phosphate deficiency has not been well characterized in moss, compared to the ordinary higher plants. The purpose of the project is to study the response of P. patens to phosphate deficiency, so as to provide reference for studying the mechanism of phosphate deficiency. In response to Pi deficiency, protonemata gave rise to a reduced number of chloronemata, but more caulonemata that were longer than for those grown on Pi medium. In addition, Pi starvation inhibited the emergence of lateral branches from elongated caulonemata. Gametophore of P. patens grown under Pi-deficient conditions firstly formed callus , and then continued to formate gametophore, with the striking increase in the length and density of rhizoid. Pi deficiency inhibits the formation of the callus whose color is relatively darker. The formed callus with many rhizoids can not continue to differentiate.MPS1 was discovered in Arabidopsis thaliana. Under Pi-deficient conditions, the axial root of Arabidopsis thaliana wild type became shorter, while the root of mps1 mutant became much shorter compared to the WT. So MPS1 gene is probably related to P, and inlvoved in the signal transduction of phosphate. Ryota Komori thought that the gene code tyrosylprotein sulfotransferases (TPSTs). Tyrosine sulfation is a posttranslational modification catalyzed by TPST. In plants, this modification is critical for the biological activities of a subset of peptide hormones such as PSK and PSY1.The potential of P. patens as a model system to study plant biological process is associated with their relatively simple developmental pattern and the dominance of the haploid gametophyte in the life cycle. Its short life cycle, easy to culture, transformant analysis and allele replacement make it an excellent material for studying plant molecular biology. The nuclear genomic DNA in P.patens exhibits a very high frequrncy of homologous recombination with the exogenous DNA, which makes gene targeting possible. Some gene targetings have succeeded and the function of these genes has been proved.In order to study the preliminaryly the biological function of MPS1 gene, we firstly constructed the MPS1 gene targeting vector. This construct was transformed into the protoplasts by PEG mediated transformation, and then the mutants were screened by G418. At last, two transformants were obtained. One is an unstable transformant, but it has obvious phenotype. It can not form gametophore, only form protonemata which is covered with microvilli. In the transformant, G418 resistance gradually disappeared and the nptII gene could not be detected. Another is a stable transformant with weak phenotype. Targeted gene replacement didn't occur by PCR detection.