小麦幼苗活性LTR反转录转座子筛选及其对非生物胁迫的响应

Screening of active LTR retrotransposons in wheat(Triticum aestivum L.)seedlings and analysis of their responses to abiotic stresses

LTR(长末端重复,long terminal repeat)反转录转座子占小麦基因组的60%以上,筛选小麦基因组中具有转座活性的LTR反转录转座子,并分析其在非生物胁迫下的响应,对研究反转录转座子在小麦抗逆境胁迫中的作用具有重要意义。本研究通过生物信息学分析,从转座子数据库(TREP database)中筛选出4个具有完整结构的LTR反转录转座子Fatima、Wis、Angela和Babara;同时利用实时荧光定量PCR(qRT-PCR)、甲基化特异PCR(methylmion specific PCR,MSP)和转座子展示(transposon display,TD)技术分别分析了它们在盐、ABA、H2O2和干旱等处理的小麦幼苗期(二叶一心)叶和根中的表达水平、甲基化水平和转座活性变化。结果表明,这4个反转录转座子在正常条件下均存在基础水平的转录,并且能够响应上述4种胁迫而发生转录水平的变化,且在相同胁迫条件下表达水平变化趋势一致。Fatima、Angela和Babara在非生物胁迫处理下表达水平的提高与其甲基化水平的降低有关,Wis则相反。反转录转座子LTR序列含有胁迫响应顺式作用元件,但在非生物胁迫条件下顺式作用元件对这4个反转录转座子的调控作用不显著。与叶相比,这4个反转录转座子在根中对胁迫的响应程度更高,且在盐和ABA处理下转座活性更强。本研究将有助于进一步揭示LTR反转录转座子对非生物胁迫的响应规律,为进一步研究利用反转录转座子进行小麦抗逆育种的遗传改良积累资料。

LTR(long terminal repeat)retrotransposable elements account for more than 60%of rye genome.It is of great significance to screen active LTR retrotransposons from wheat genome and analyze their transposition,the relative expression levels,and methylation levels under abiotic stress in exploring the role of retrotransposable elements in improving wheat anti-stress ability.Four active LTR retrotransposons(Fatima,Wis,Angela,and Babara)with complete structure were selected from the TREP database by bioinformatics analysis.The relative expression levels,methylation dynamics,and transposition activity of the four LTR retrotransposons were then analyzed at seedling stage(two leaves with one heart)leaves and roots of the stress-treated(NaCl,ABA,H2O2,and PEG)wheat seedlings by qRT-PCR,methylation-specific polymerase chain reaction(MSP),and transposon display method.The results suggested that the four retrotransposons had basic transcription activity under normal conditions,which could be changed under stress conditions,and their variation tendency was similar in the same stress conditions.The up-regulation of Fatima,Angela,and Babara was due to their down-regulated methylation levels,while Wis was opposite.The 3′LTR of LTR retrotransposons contained many stress-responsive cis-elements,but the regulatory effect of which were not obvious under stress treatments.Compared with that in leaves,the four LTR retrotransposons in roots were more sensitive to stresses and had higher transposition activity.This study will help to further reveal the response regularity of LTR retrotransposons under stress conditions and accumulate data for improving of stress resistance breeding wheat by using transposable elements.