Analysis of the mechanism and induction of usefull somaclonal variations in plant breeding

1.从水稻愈伤组织中衍生出的第二代再生体（Oryza sativa cv.）Akihikari)。有的子代分化为白化、黄斑、条纹和白化等多种突变体。这些突变基因可能属于细胞核基因组。在长期培养中获得了半矮秆、早穗的后代，这对水稻育种具有重要意义。在含烟叶提取物的培养基上培养烟叶愈伤组织。正常染色体数（2n=24）的细胞出现频率显著高于不添加叶提取物的细胞。利用根癌农杆菌将抗湿素基因（HYG^R）切到中间的GUS基因转化到烟草愈伤组织中。通过重组同源DNA序列，在根、茎和叶中恢复了GUS活性。这表明重组发生在染色体内。在水稻中发现了与玉米MuDR转座子部分同源的基因组克隆。然而，该克隆在水稻细胞培养中没有恢复转座因子的活性。对大豆幼苗进行紫外线照射，利用RT-PCR扩增出查尔酮合成酶基因家族的特殊区域。所有基因家族均有RNA扩增，以5号基因扩增最为明显。利用组织和细胞培养技术培育抗UV-B植物的准备工作正在进行中。

1.In the second generation of regenerants derived from the calli of rice (Oryza sativa cv. Akihikari).some progenies segregated into several mutants such as albino, xantha, stripe and alboviridis. These mutant genes may belong to the nucleus genome. In the long term culture we obtained progenies with semidwarf and early heading which may be very important for the plant breeding of rice.2.The calli of Nicotiana sylvestris were cultured on the medium containing the young leaf extract of N.sylvestris. The frequency of cultured cells with normal chromosome number, 2n=24, were significantly higher than the cells cultured on the medium without the leaf extract.3.The GUS gene cut in the middle by hygromicin resistant gene (HYG^R) were transformed to the tobacco callus by using agrobacterium tumefaciens. The GUS activity recovered by the recombination of homologus DNA sequences was observed in root, stem and leaf. This indicates that the recombination occurs within a chromosome.4.The genomic clone which is partially homologus with the MuDR transposon of corn was found in the rice. This clone, however, did not recover the activity of transposable element in the cell culture of the rice.5.The seedlings of soybean were applied by the ultraviolet rays (UV-B) and then special regions of RNA (chalcone syntase gene family) were amplified by RT-PCR.The amplification of RNA was observed in all gene family, especially No.5 gene. Preparation for the development of UV-B resistant plant induced by tissue and cell culture is now on the way.