摘要
研究了苹果基因组中Ty1-copia类逆转座子的转录活性、多样性及其甲基化水平。在培养基MS+2,4-D2mg/L+BA0.2mg/L+NAA0.5mg/L上诱导了1个月的愈伤组织中用RT-PCR方法检测到了270bp的目的条带,而对照、继代组培苗和不含2,4-D的愈伤中均没有目的条带的扩增,说明一定浓度的2,4-D可以诱导苹果中Ty1-copia类逆转座子的表达活性。将目的条带回收、克隆和测序后进行分析:所克隆的21条序列虽都为Ty1-copia类逆转座子逆转录酶保守序列,但存在很大的异质性,21个克隆的核甘酸序列变化范围为196-290bp;翻译成氨基酸后存在缺失、插入、移框和终止密码子突变,7个克隆在氨基酸保守序列‘SLYGLKQ’处有1-2氨基酸位点的突变,说明这些序列对应的逆转录酶多数可能已失去了其原有功能。将21条序列进行聚类分析,除ART20外,其它克隆可聚为3类,并分别与GenBank上某些物种的相应序列同源性很高,表明在不同物种间可能存在逆转座子的横向传递作用。甲基化试验表明苹果基因组内Ty1-copia类逆转座子甲基化水平高。这些都表明Ty1-copia类逆转座子对苹果基因型的多样性及基因组的进化具有重要意义。
Transcriptionally active Ty 1-copia-like retrotransposons were found in apple callus cells propagated on MS solid medium supplemented with 2 mg/L of 2,4-D, 0.2 mg/L of BA and 0.5 mg/L of NAA for a month. RT-PCR was used for amplifying the conserved reverse transcriptase domain of about 270 bp. Twenty-one clones isolated from the callus cells were sequenced and showed high heterogeneity. All 21 clones were different from each other, amino acid ranging from 35.6% to 98.8%. The majority of isolated reverse transcriptase gene were found to lost their function, containing stop codons, frame shifts, deletion, and insertion mutations. The SLYGLKQ, characteristic of plant retrotransposons, contained base substitution mutation in 7 clones. Horizontal transmission of plant retrotransposons had occurred in the past. Searching through the protein GeneBank database, all 21 sequenced clones showed high homology to Tyl-copia-like elements belonging to other plant species. A phylogenetic tree was constructed based on their predicted amino acids. All sequences were divided into three groups, except ART20. Some Tyl-copia-like copies, present in apple, were found to be high methylated. In conclusion, retrotransposons characteristics have contributed to the genetic diversity and evolution of their host species.
出处
《果树学报》
CAS
CSCD
北大核心
2005年第5期441-445,共5页
Journal of Fruit Science
基金
国家自然科学基金资助项目(30200190)
作者简介
孙俊，女，在读博士生。
Author for correspondence. E-mail： Zhangzhen_nj@hotmail.com;Tel：025-84385724。
