Co-expression of MtDREB1C and RcXET Enhances Stress Tolerance of Transgenic China Rose (Rosa chinensis Jacq.)

The xyloglucan endotransglycosylase gene RcXET of China Rose (Rosa chinensis Jacq.) and the MtDREB1C gene of Medicago truncatula Gaertn. were pyramided into the plant expression vector pBin438 and transformed into China Rose. Southern blot and Northern blot analyses showed that the heterologous gene MtDREB1C was integrated into the genome of surviving transgenic rose plants and expressed at different levels. Real-time PCR analysis demonstrated that robust expression of the congenetic gene RcXET was activated in the five surviving transgenic rose plants. The performance of the five transgenic lines under freezing and drought stress was superior to that of non-transformed controls. Thus, pyramiding of the genes MtDREB1C and RcXET in China Rose was more effective to enhance freezing and drought tolerance than untransformed controls. A positive correlation was observed between the expression of RcXET and the growth rate in contrast to the non-transgenic plants. The physiological assay showed that co-expression had greater effects on EC%, contents of proline, soluble sugar, photosynthesis rate, negative water potential, and turgor loss point than activities of POD and SOD under stress. The study also highlights the utility of a simple and rapid approach to express two or even more genes in one expression vector.