Transgene Stability Of Transgenic Hybrid Of Populus [(Populus Tomentosa ×P.bolleana)×P.tomentosa] And Its Effect On Soil Microorganisms

Populus tomentosa Carr.is an indigenous tree species in China and widely employed for forestation and landscape in northern China.However,it can't grow normally when the concentration of salt attains to 0.3%in soil.That was one of reasons why the distribution of P.tomentosa was confined. To improve the salt-tolerant ability,the AhDREB1 gene was successfully introduced into triploid hybrid of Populus((Populus tomentosa×P.bolleana)×P.tomentosa) in our laboratory,and the transgenic trees were restrictively field released.Because of the ecological risks of transgenic plants,it's necessary to evaluate the biosafety of transgenic plants at all aspects scientifically before they were released into environment.Transgene stability,effect on species and quantity of microorganisms in soil after planting and horizontal gene transfer are important parts of evaluating biosafety risks in transgenic plants.The material of this study is transgenic hybrid of Populus((Populus tomentosa×P.bolleana)×P. tomentosa) carried 35S:AhDREB1 gene which has been planted in Dongying city Shandong province for more than 3 years.By using real-time PCR technology,transgene copies and its expressions at transcription level in different organs were analyzed.The results show that AhDREB1 gene was still in the transgenic trees,and its copies were not obviously different among different trees;and AhDREB1 gene transcriped in all organs,there were also no obvious difference among different trees and organs. The transgenic trees were tissue cultured at different concentration of salt,it turn out that transgenic trees were obviously more salt-tolerant than non-transgenic trees,transgenic trees in vitro grew normally when the concentration of salt was less than 0.5%,and still survived but grew slowly when the concentration of salt was between 0.5%to 0.7%.The rusults of molecular detection and phenotype analysis were both prove that AhDREB1 gene was stable in genome of the transgenic trees and can express functionally,no transgene silence was detected.Using flat dilution to survey three groups of microorganisms(bacterium,actinomyces and epiphyte) in the soil around the roots of both non-and transgenic trees,a little differences were found in terms of the number of microorganisms between non-and transgenic trees,but analysis of variance results show the differences were not significant,so it can be concluded that planting of the transgenic trees has no significant effect on species and quantity of microorganisms in soil yet.Furthermore no alien target DNA was detected from PCR products of total soil DNA and strains DNA amplified with specific primers of AhDREB1.It indicated that AhDREB1 gene had not horizontal transfer into microorganisms in soil yet.This study tested the transgene stability,effect on species and quantity of microorganisns in soil and the possibility of transgene horizontal transfer after triploid hybrid of Populus((Populus tomentosa×P.bolleana)×P.tomentosa) carried AhDREB1 has been field released.The purpose of this study is to evaluate other ecological risks of the transgenic trees before they make pollen,and provide references for extensive release of the transgenic trees into environment and making scientific and secure management scheme of transgenic forestry.