Study On Genetic Transformation Of 1-SST Gene To Sugarcane And Its Drought Resistance Ability

Fructan is a kind of polymer of fructose molecules synthetized by fructosyltransferases(FTs) using sucrose as the substrate, exists to 15% of angiosperms. Fructan has important physiological function during abiotic stress in addition to being a kind of storage carbohydrate. As an osmoregulation substance, fructan prevents cell water loss during abiotic stress such as drought and salt. Fructan prevents membrane from fusion by interactting with polarity head of phospholipid bilayer, inhibiting membrane become colloidal, thus keep the stability and fluidity of cell membrane. Fructan metabolism is an important regulation mechanism of plants during environmental stresses. Accumulation of fructan can improve plant resistance to a variety of environmental stresses. Meanwhile, fructan is an excellent source of soluble fiber, perfectly consistent with the typical standard of prebiotics bifidus factor and has health promotion for human beings.Fructans are synthesized by the collective action of FTs. In the first step, sucrose: sucrose-1-fructosyltransferase(1-SST) catalyzes the initial fructosyl transfer between two sucrose molecules, forming a GF3, and releasing a glucose. Further chain elongation is catalyzed by other types of fructosyltransferases (1-FFT,6G-FFT and 6-SFT,etc), addingβ(2,1)-orβ(2,6)-linked fructofuranosyl units.There are many reports about enhancing plant stress resistance through transfer fructosyltransferases gene like 1-SST, 1-FFT into plants. Sugarcane is main raw material of sugar and has abundant substrate for fructans synthesis, thus sugarcane is ideal material for transforming ructosyltransferases gene.We’ve got 35 sugarcane plants tranfered with 1-SST driven by tomato promoter rbcS from preliminary study of 1-SST. Based on this, my study carried out the following molecular and physiology identification. After PCR and RT-PCR detection, 5 RT-PCR positive plants were chosen for fructans determination by HPLC. GF2 was detected in the 5 rbcS:1-SST transformed plants. Fructans accumulation increased drought and salt tolerance, as shown by the stress physiological indexes, such as the rate of bound water/free water, plasma membrane permeability, malondialdehyde content, chlorophyll contents and activity of SOD. These results suggest that sugarcane transformed with the 1-SST gene can accumulate catalysate of 1-SST,GF3, and have enhanced tolerance of transgenic sugarcane to drought and salt.The root plays an important role on drought, salt and chilling resistance of plants. In order to improve sugarcane stress resistance through 1-SST transforming. Taking the place of rbcS, we constructing 1-SST plants expression vector using sugarcane pPST2a promoter, which was proved to have a higher expression level in sugarcane roots. Transfered 1-SST driven by pPST2a into sugarcane callus through Agrobacterium-mediated method, we got 93 PCR positive seedlings. Parts of seedlings were picked out for drought and salt tolerance experiments. Compared with untransgenic sugarcane, the transgenic seedlings have better salt and drought tolerance ability. More experiments will be done after the transfered seedlings grow up.