Abstract: To evaluate the copy number ofCtDXRgene in transgenicNicotiana benthamianaand further analyze its tolerance to salt and heat stress, Southern Blot was applied to determine the copy number of theActingene in wild-typeN. benthamianaand the copy number of theCtDXRgene inCtDXRtransgenicN. benthamianawas detected by real-time PCR withActingene as reference gene. Then, the salt and heat tolerance ofCtDXRtransgenicN. benthamianawas analyzed. According to the PCR-dependent method, 10 of T1 transgenicN. benthamianawere randomly detected and all of which obtained positive results, indicating thatCtDXRhas been successfully transformed. TheActingene is a single-copy gene in the genome of wild-typeN. benthamiana. 80% of transgenicN.benthamianawere determined as single-copy or low-copy lines.CtDXRtransgenicN. benthamianashowed better performance, such as plant height (P<0.01), number of lateral roots (P<0.01), and fresh weight (P<0.001), than wild-typeN. benthamianaunder salt stress, whereasCtDXRtransgenicN. benthamianaexhibited better performance, such as plant height (P<0.01), number of leaves (P<0.01), and fresh weight, than wild-typeN. benthamianaunder heat stress. Taken together,CtDXRconferred salt and heat tolerance toN.benthamiana. In this study, a method to detect copy number of foreign gene in transgenicN. benthamianawas established, by which the copy number ofCtDXRgene in transgenicN. benthamianawas accomplished. Moreover,CtDXRgene was preliminarily identified to have salt and heat tolerance.

Key words: Nicotiana benthamiana, 1-deoxy-D-xylulose-5-phosphate reductoisomerase, copy number；Southern Blot, quantitative real-time PCR