表达阳离子抗菌肽的转基因棉花表型异常

用基因枪轰击茎尖法将人工合成的阳离子抗菌肽CEMA基因导入棉花中，获得3株转基因棉花，它们均出现嵌合体表型。在表型不正常的枝条上，叶片扭曲畸形，出现灰绿色与绿色条纹相间的花叶，花器发育异常、无花粉、人工授粉不能结实。花叶区的叶绿素含量降低约20％，叶肉栅栏组织细胞局部缺损，维管束及其管状分子数目减少。叶片灰绿色区叶肉细胞的次生壁明显增厚，局部区域吞噬现象明显，叶绿体内基粒片层数目较少，嗜锇小体明显较多，类囊体腔不明显。PCR分析表明，仅在不正常枝条的花叶中检测到外源CEMA基因。

Abnormal Phenotype in Transgenic Cotton Plant Expressing Cationic Peptide (CEMA)

Three chimeric transgenic cotton plants were produced by bombardment of cotton shoot tips using BioRad particle gun with gold particles, coated with precipitated DNA containing the gene for CEMA (a cationic peptide). The microscopic observation of leaves was done. The ultrastructure was examined using H-600I electron microscope. Each of the three plants consisted of abnormal and healthy shoots. On the abnormal shoots, the leaves were mosaic (with grayish green and green) and uneven, the epicalyx, petals and style were tortuous, the ovule was shrunken, the number of anther were smaller, and there was no pollen on the anther (Fig. 1). So the flowers were sterile. The leaves, flowers and bolls in the healthy shoots were the same as those in the wild type plants. In mosaic regions, the chlorophyll contents dropped by 20% (Table 1), the palisade tissue absented partly and the vascular tissue degenerated to some degree (Fig.2). Submicroscopic observation revealed that the structures of nucleus, mitochondra, endoplasmic reticula, Golgi body and microbodies were not affected strikingly by the introduction of CEMA gene, however phagocytosis was active in some parts and the secondary walls of mesophyll cells were strengthened. Some interesting changes in the chloroplast were found in greyish green parts. Although the basic structure of chloroplast appeared to be normal, the number of stocks in granum was abnormally smaller with aggregation of osmiophilic globules and a near absence of thylakoid lumens (Fig.3). All the abnormalities observed in the CEMA transgenic cotton plants may be explained as: (1) Because of the similarity of membrane between thylakoids and microorganism, the CEMA , designed to damage the membrane of microorganism, inserted into the thylakoid membranes, formed channels in the membranes. The fluid in thylakoid lumens leaked out, the thylakoid lumen vanished and the normal functions of the chloroplast were disturbed. (2) The damages caused by CEMA triggered the expression of host plant defense systems, which resulted in strengthening of cell wall and other changes.