Effects Of ATG990 And Its Homologous Gene On The Early Growth And Development Under Stress Conditions In Arabidopsis

In the process of development and growth, the plant will be affected by many negative factors and growth environment, these environment factors of negative growth are called abiotic stress or adversity.There are many factors which affect the growth of plants especially at high salt conditions. In agricultural production, frequent irrigation can make the salt accumulation of the soil followed with water transpiration,and resulting in decreased water potential, the plant with low water potential will become difficult to obtain water and inorganic salt from the soil, leading to plant in a water deficient environment, which will greatly influence the crop yield.Our previous study showed that, RSSG58 gene which was mainly expressed in rice sperm cells, and RSSG58 protein showed high homology with Arabidopsis myosin heavy chain protein. Myosin is widely existed in plants and animals, participate in the cyclosis, organelle movement, material transport and mitosis process. Bioinformatics analysis revealed that RSSG58 was expressed significantly higher in pollen grains, root seedling stage and mature leaves than other parts of plant, so RSSG58 gene may play an important role in rice growth. The expression level of RSSG58 was also changed under salt treatment,showed that RSSG58 may take part in the salt stress response pathway. There are two RSSG58 homolog genes in Arabidopsis, ATG58 and ATG990. So it is very interesting to discover how these genes get involved in salt stress and signal transduction pathways, or explain how the myosin proteins take part in stress on plant growth under stress conditions through ATG58 and its homologous gene mutants’ phenotype and gene expression analysis.In this study, we obtained the T-DNA insertion mutants, overexpression mutants and revertant mutants of ATG58 and ATG990 genes. By treated them with high salt, osmotic stress and plant hormones, the rates of germination, cotyledon greening, root elongation and early growth phenotypes were analyzed, and the results showed that the growth of wild type plant and atg58 mutant were similar in normal conditions,while atg990 mutant germinated later than wild type plant. But in the condition of salt stress and abscisic acid treatment, both mutants showed inhibited phenomenon at the seed germination and seedling growth compared with the wild type plant. The cotyledon of atg990 mutant turned green earlier than that of wild type when treated by NaCl at 100 mM, while seedling growth was insensitive to the salt stress. Based on the analysis of related genes under salt stress, the expression of them in the atg990 mutant was significantly changed. So it is indicates that the ATG58 gene is involved in the tolerant pathway of salt salt stress. In addition, ABA treatment can restore the phenotype of atg990 mutant on germination delay in normal MS plate, and the expression level of ATG990 in ABA-insensitive mutants abi4-1, abi5-1 were significantly increased, suggesting that the ATG990 gene was involved in the regulation of seed germination through ABA pathway.