Expression Of Atfad8 Gene In Tobacco Choroplast Genome

Chilling stress affects seedling growth of tobacco, causes the loss of tobacco quality and yield.It is important to improve chilling tolerance of tobacco seedlings. The biologic membrane was regarded as the position which is firstly suffered damage under low temperature stresses.The content of unsaturated fatty acid in plant membrane lipids was higher,the temperature of transition of membrane lipids was lower and the chilling tolerance of plans was stronger.fad8 gene encodingω-3 fatty acid desaturase.Omega-3 fatty acid desaturase was the key enzyme which catalyzed 16:2(7,10)or 18:2 (9,12)to form 16:3(7,10,13)or 18:3(9,12,15).The change of its content can influence the composition of membrane lipid,especially the level of TAs.Then it can affect the temperature of transition of membrane lipids and change the tolerance under low temperature stresses.In this study, we transformed Atfad8 gene in to tobacco chloroplast genome and investigated the responses of transplastomic tobacco to low temperature stress. The main results were as follows:1. Atfad8 gene had been integrated into tobacco chloroplast genome, which verified by PCR and southern blot analysis.2. The change of membrane lipids in transplastomic plants leaves mainly occurred in the content of 18:2 and 18:3. Compared with WT plants, the transplastomic plants in which Atfad8 gene was over-expressed had low content of 18:2 and high content of 18:3. Over-expressed Atfad8 gene in the transplastomic plants promoted the conversion of 18:2 to 18:3.3. The test about physiological indicators of cold-resistence showed that the cold-resistence ability of the transplastomic tobacco were higher than the wild type tobacco.By superoxidedismutase(SOD),catalase(CAT),peroxidase(POD), malondialdehyde(MDA)content,praline content,soluble protein content,soluble sugars content into plants reflected the cold-resistance has significantly enhanced.