Effect Of SOS1 RNAi On Thellungiella Halophila

Soil salinity is one of the most significant abiotic stresses for crop plants in agriculturalfields worldwide. High levels of sodium ion (Na~+) are toxic to plants because of their adverseeffects on celluar metabolism and ion homeostasis. Therefore, maintaining low levels of Na~+ inthe cell, specifically in the cell cytosol, is essential for plants. Plants are thought to remove Na~+from the cytoplasm by transporting it into the vacuole or out of the cell using Na~+/H+exchangers localized in the vacuolar and plasma membranes, respectively. SOS1 encoding aplasma membrane Na~+/H~+ antiporter and AtNHX1 encoding a vacuolar Na~+/H+ antiporter wereisolated from glycophytic Arabidopsis thaliana, and overexpression of AtNHX1 and SOS1 inArabidopsis thaliana increased the salt tolerance of transgenic plants significantly. Themodulate mechanism of the SOS signal pathway consisted of SOS1,SOS2 and SOS3 inArabidopsis has been illuminated, studies showed that the SOS signal pathway plays animportant role in ion homeostasis and salt tolerance of plants. As a close relative ofArabidopsis, Thellungiella halophila is able to withstand dramatic salinity shock up to 500mm NaCl and grow in salt far in excess of the capability of Arabidopsis. This plant does notproduce salt glands or other complex morphological alterations either before or after saltadaptation. It appears that salt tolerance in Thellungiella halophila is largely the result of basicbiochemical and physiological mechanisms. So gene silence study of SOS1 in Thellungiellahalophila is important for reveal the base of salt tolerance mechanism of halophyte.RNAi of SOS1 from Thellungiella halophila have been constructed, and ThSOS1-pGSA1252 has been transferred into Agrobacterium tumefaciens GV1101. Thellungiellahalophila was transformed with by floral-dip method, and T1 transformants were screenedwith herbicide Finale?(formerly named Basta),in which the active gredient is glufosinateammonium. Finally,15 Basta-resistant lines were acquired, and a wealthy of transformed T1seeds were harvested.The molecular identification of these Basta-resistant plants are as below:1. PCR result showed that all Basta-resistant plants had strong positive signals, and nosignal was shown in wild type plants.2. Real time PCR results showed that the SOS1 RNA decreased in different transformedplants when treated with or without NaCl.Transformed and wild type plants (control) were evaluated for salt tolerance.1. On MS medium containing different concentration of NaCl (0-300mmol/L), silence ofSOS1 in Thellungiella halophila decreased salt tolerance.2. By comparing the difference of SOS1 RNA level and salt tolerance level oftransformed and wild type plants, it is found that the more the SOS1 RNA level decreased, themore salt sensitive the plants showed.3. After the treatment of different concentrations NaCl (0-400mmol/L), the growth statusof the transgenic lines was dramatically worse than that of wild type plants.4. In this study, the transgenic plants showed a tendency to accumulate more Na+ undersaline condition than wild type plants do.5. In this study, the transgenic plants showed a tendency to produce more MDA undersaline condition than wild type plants do.From the above results it is concluded that gene silencing of SOS1 in Thellungiellahalophila decreased its salt tolerance, and SOS1 plays an important role in exporting Na+during T. halophila adapting to saline environment.