一个毛竹LTR反转录转座子结构鉴定及表达模式分析

Identification and expression pattern analysis of a Moso Bamboo LTR retrotransposon

摘要:

为了在毛竹中开发更多的活性LTR反转录转座子，文中分析和鉴定了一个毛竹LTR反转录转座子 (Ph-LTR2)，系统分析了该转座子在逆境下的表达模式。Ph-LTR2转座子全长6 030 bp，属于Ty3-Gypsy家族中的Reina亚家族。LTR序列同源性为96.41%，插入时间约为61.92万年，在基因组中有5个拷贝。Ph-LTR2转座子结构域包括GAG (种属特异抗原，gag protein) 蛋白域、PR (蛋白酶，Proteases) 蛋白域、RT (反转录酶，Reverse transcriptases) 蛋白域、RH (RNA 酶H，Ribonuclease H) 蛋白域、INT (整合酶，Integrase) 蛋白域和CHR (染色质组织修饰域，Chromatin organization modifier) 蛋白域。通过实时定量PCR检测了INT、RT和RH的表达模式，确定INT、RT和RH在毛竹叶、笋、根存在组织表达特异性。在高温、低温、甲基化抑制剂、辐照与高盐等胁迫下，Ph-LTR2转座子INT、RT和RH的转录水平均不同程度地提高了，具体来讲，INT、RT和RH在高温、低温、甲基化抑制剂处理后转录水平上调；在低剂量辐照处理和低浓度盐溶液处理后转录水平也上调，但随剂量和浓度的增加表达水平又下降，这些结果表明Ph-LTR2转座子的表达模式响应外界环境的变化，但具体机制尚不清楚。本研究结果为开发基于Ph-LTR2转座子标签奠定了一定的理论基础。

Abstract:

To develop more active LTR retrotransposons in Phyllostachys edulis, a Ph. edulis LTR retrotransposon (Ph-LTR2) was identified, and the expression pattern of the transposon under stress was systematically analyzed. Ph-LTR2 transposon is 6 030 bp in length and belongs to the Reina subfamily in the Ty3-Gypsy family. With the similarity of 96.41% of both LTR sequences, the Ph-LTR2 transposon inserted the moso bamboo genome about 61.92 thousand years ago. There are 5 copies identified in the genome. The Ph-LTR2 transposon domain includes GAG (gag protein) protein domain, PR (Proteases) protein domain, RT (Reverse transcriptase) protein domain, RH (Ribonuclease H) protein domain, INT (Integrase) protein domain and CHR (Chromatin organization modifier) protein domain. The expression patterns of INT, RT and RH were detected by real-time quantitative PCR. The three domains were found to have specific expression patterns at different tissues of the bamboo. Under the conditions of low/high temperature, methylation inhibitors treatments, irradiation and high salt stress, transcription levels of the three domains of the Ph-LTR2 transposon increased with different degrees. Specifically, after treatment with low/high temperature and methylation inhibitors, the transcription level was up-regulated; after low dose radiation treatment and low concentration of salt solution treatment, the transcription level was also increased, but the expression level decreased with increasing dose of radiation and concentration of salt solution. These results indicate that the expression pattern of the Ph-LTR2 transposon responds to the changes of the external environment, but the exact mechanism is not yet known. The results of this study laid a certain theoretical foundation for the development of the genetic tool based on Ph-LTR2 transposons.