地衣中共生念珠藻多拷贝序列的初步分析

The primary study on multicopy of ITS sequences of Nostoc in lichens

地衣是一类菌和藻的共生植物.本文选用共生念珠藻为研究材料,测定了其ITS(16S rDNA至23SrDNA基因间隔区)序列,结果表明地衣中共生念珠藻ITS基因存在着多拷贝现象,在所得的四条谱带中,前三条和自由生长的念珠藻一样,另一条约为920bp,是最长的谱带.序列分析结果显示,在共生念珠藻中,各拷贝之间的ITS序列在结构和碱基组成上都存在着差异,其中ITS-S中仅包含tRNA-Ala基因,在ITS-L中包含tRNA-Ala和tRNA-Ile,这一现象说明各拷贝之间在分子进化上存在着不同步现象.虽然许多工作还在进一步的探讨中,我们初步认为这种多拷贝的形成是由于不等交换产生的.

Lichens is a kind of fungus and algae symbiosis plant. This paper selected Nostoc, which is symbiont in lichens, as the materials to study the ITS（ 16S rDNA- 23S rDNA interval space sequences）sequences. The results indicated that the ITS sequences are also multicopy genes as those in free-living Nostoc. The three front bands are the ~me as them in free-living Nostoc, but the forth band（Longest band about 920bp） is only found in this study. We can know there are differences gene constructions and sequences in the different copies by ITS sequences analyzed. ITS - S only includes tRNA^-Ala coding region, but ITS - L include both tRNA^-Ala and tRNA^-Ila coding regions. These results from this paper illuminate there are different molecular evolutionary steps among those ITS copies, although it is needed to further study.