Stability Of Transgene In Micropropogation Plants Of Transgenic Birch

In this paper,we selected transgenic birch(Betula platyphylla) plants which have been cultured under natural environmental conditions over a period of 7 years.Multiple-PCR,Northern bloting,RT-PCR and ElISA were used to detect the stability of transgene inheritance and expression in micro-propagation plants of transgenic birch.The main results summarized as follows:1.The micro-propagation of transgenic birch could be regenerated by axillary bud and callus induction.Result of multiplex PCR showed extraneous genes integrated stably in regenerated plants..Transcriptional expression of bgt and gus gene in transgenic birch regenerated plants was analysed by Northern blot.The results showed transcriptional expression of bgt and gus gene GUS activity were stable in transgenic birch plants derived through a cycle of dedifferentiation and then differentiation.2.To determine the effect of subculture on transcriptional level of bgt and gus gene in regenerated plants of transgenic birch,The 15 successive subcultures were examined.With the increase of subcultures,the expression level of extraneous genes in regenerated plants was more and more lower.The result of GUS detection demonstrated 50%of them showed a low rate of silence,30%of them showed a high rate of silence,only transgenic birch TP91 remained expression until the 15th subcultrue.3.Many factors,such as environmental factors,can influence the stability of the expression of foreign gene in different developmental stage.Under the conditions of high temperature stress (37℃),the expression level of transgene decreased gradually.In the darkness condition, transcription level of transgene increased gradually and got to the highest point after 72 h.And there were no obvious change in transgene expression in different light condition.4.We used 5-Azac first in culture of transgenic wood to detect the relationship of the transgene-silence and DNA methylation.5-Azac treatment had significant influence on micro-propagation plants.TGS in regenerated plants could be reactivated by high concentration(100-1000μmol·L^-1) 5-Azac treatment.The decrease of expression level with the increase of subcultures was associated with DNA methylation.