Studies on the biosafety assessment of transgenic plants(3/4)

We have produced transgenic Eucalyptus camadulensis carrying the Populus tremuloides cinnamate 4-hydroxylase(C4H) gene. These transgenic plants are obtained by Agrobacterium-mediated transformation in which the transgene is driven by the 35S promoter. No evidence exists for gene transfer from plants into microorganisms or for horizontal gene movement. Escape through tree naturalization and escape through hybridization can be much more a problem. One of the most discussed environmental effects associated with the use of transgenic trees is the loss of control over the engineered genes. Flowering and pollen dispersal are important for outcrossing of the genetically engineered trait. An escape of transgenes is commonly by pollen because it is a major element of the reproductive system that is designed for gene movement. The biosafety assessment will be carried out successively in semi-containment greenhouse and isolated field trials. The most important step is to fully understand the characterization of the GM plant and the function and mechanism of the trangenes. The aim of this study is to determine the gene movement by self-pollination in a transgenic tree of E. camadulensis. In addition to these, gibberellins and cytokinins are the plant growth substances most likely to be closely implicated in at least several aspects of the flowering process. However, changes in endogenous gibberellins and cytokinins during flower development remain essentially unknown, especially in Eucalyptus camadulensis. The content of endogenous gibberellin and cytokinin in Eucalyptus camadulensis at vegetative growth, early floral initiation, and flower development stages will be investigated. We will also determine the influence of paclobutrazol treatment on the shoots at different development stage in relation to floral initiation.本研究构建了携带美洲山杨(Populus tremuloides)肉桂酸-4-羟化酶(cinnamate 4-hydroxylase, C4H)基因的转基因细叶桉(Eucalyptus camadulensis)。该转基因植株通过农杆菌介导的转化获得，外源基因由35S启动子(35S promoter)驱动。目前尚无证据表明基因可从植物转移至微生物，亦未发现水平基因流动现象。而通过植株自然归化以及杂交介导的基因逃逸则是更为突出的环境风险。围绕转基因树木应用所引发的诸多环境影响中，讨论最为广泛的议题之一便是工程化基因的可控性丧失。开花过程与花粉扩散对于转基因性状的异交过程至关重要，而转基因逃逸通常经由花粉介导——花粉作为植物生殖系统中负责基因流动的核心载体，其传播是转基因逃逸的主要途径。本研究将依次在半封闭温室与隔离田间试验中开展生物安全评价，其中首要步骤是全面解析转基因(Genetically Modified, GM)植物的特征，以及转基因(transgenes)的功能与作用机制。本研究的核心目标是明确转基因细叶桉通过自花授粉实现的基因流动情况。此外，赤霉素(gibberellins)与细胞分裂素(cytokinins)是目前已知至少在开花过程多个环节中发挥关键调控作用的植物生长物质，但目前对于花发育过程中内源赤霉素与细胞分裂素的动态变化仍知之甚少，尤其是在细叶桉中。本研究将检测细叶桉在营养生长、成花起始以及花发育三个阶段的内源赤霉素与细胞分裂素含量，同时还将明确多效唑(paclobutrazol)处理对不同发育阶段枝条成花起始的影响。