The Function Investigation Of Rhizophagus Irregularis HOG1 Under Osmotic Stress

Soil salinization is one of the most widespread stress phenomena on plant growth in the world. Since most of the plants are salt-sensitive, soil salinization could result in the reduction of the crops productivity and diversity. Arbuscular mycorrhizal fungi(AMF) can symbiose with 80% higher terrestrial plants. Arbuscular mycorrhiza(AM) symbiosis is biotrophic and also(usually) mutualistic, AMF have to depend on the carbon source provided by host plants to survive. In return, AMF could assist host plants to enhance the absorption of mineral nutrition elements, and to resist adverse environments such as osmotic pressure.The physiology and biochemistry effects which AM fungi could assist host plants to resist osmotic pressure have been extensively investigated, however, the molecular mechanism is still poorly understood.HOG1 is a high osmotic glycerol response gene reported in many species. According to R.irregularis DAOM 197198 genome sequence reported in GenBank, we coloned the open reading frame of R. irregularis(AH01) HOG1 gene(R.iHOG1) and investigated the function of R.iHOG1 in response to salt stress. Finally, a series of results were obtained:1. The functional complementary experiments of Saccharomyces cerevisiae ScHOG1 deletion mutant demonstrated the expression of R.iHOG1 gene in yeast could complement the phenotype of the S.cerevisiae mutant, increasing tolerance to osmotic stress.2. In order to further explore the molecular mechanism that R.i HOG1 assist host resistance to osmotic stress, the EGFP subcellular localization strategy was employed. R.i HOG1 was found to transfer to the nucleus from the cytoplasm once cell when subjected to osmotic stress, indicating that R.iHOG1 might activate the expression of other resistence-related gene in the downstream of the signal transduction pathway by binding with transcription factors.3. R.irregularis AH01 and Medicago truncatula co-cultured under NaCl stress leaded to about two- fold increasement of the expression of R.i HOG1, which indicated that R.iHO G1 involved in the osmotic resistance process in the AMF-plant symbiosis system.4. The expression of R.i HOG1 in R. irregularis AH01 and M. truncatula system was repressed by Host Induced Gene Silencing(HIGS) strategy. The results of diramatical decline on mycelium density and the too early degradation in arbuscule indicated that R.i HOG1 may involve in establishing and maintaining the AM symbiosis.All results in this study revealed that R.i HOG1 participated in anti-osmotic stress process in AM, which provided new knowledge for research of super-hypertonic response mechanism in R.irregularis.