高原鼢鼠prestin基因的组织特异性表达与适应地下生活的关系

摘要

高原鼢鼠是青藏高原特有的地下鼠,地下鼠具有准确的空间定位能力.Prestin蛋白是在耳蜗特异性表达且与回声定位有关的蛋白分子.为了探讨prestin基因与高原鼢鼠地下空间定位之间的关系,我们克隆了高原鼢鼠prestin基因的编码区序列,并与其他物种的prestin基因进行序列比对;运用PAML软件对高原鼢鼠的prestin基因进行进化分析;根据已克隆的序列,应用实时荧光定量的方法测定高原鼢鼠耳蜗、尾部、足垫和鼻垫组织中prestin基因mRNA的表达水平.研究结果表明,与人、大鼠、小鼠、裸鼢鼠、家兔和牛6种哺乳类动物相比,高原鼢鼠prestin基因编码的氨基酸序列显示存在9个氨基酸残基突变;Test 2模型未检测到统计上显著的正选择位点;高原鼢鼠耳蜗prestin基因mRNA的表达水平显著高于高原鼠兔(P＜0.05),高原鼢鼠耳蜗和尾部prestin基因mRNA的表达水平显著高于足垫和鼻垫(P＜0.01).以上结果说明,prestin基因不仅在高原鼢鼠耳蜗中表达,而且在尾部、足垫和鼻垫组织中也有表达.高原鼢鼠在地下洞道生活过程中,可能利用尾巴、前后足和鼻子辅助感知低频声波,从而准确地进行空间定位.%The Plateau zokor (Eospalax baileyi) is a typical subterranean mole rat in Qinghai-Tibet plateau.Subterranean mole rat is a kind of animal which has the ability to orient space accurately.Prestin expressed specifically in cochlea is the protein related to the echolocation.In order to shed light on the relationship between prestin and underground spatial orientation of plateau zokor,the CDS sequence of plateau zokor prestin gene was cloned and compared with other species.The software PAML was used to analyze the adaptive evolution of amino acid sites in the prestin of plateau zokor.The expression levels of prestin mRNA in cochlea,tail,paw and nose were determined with real-time PCR according to the cloned sequence.The results indicated that the CDS sequence of the plateau zokor prestin was similar to those of six kinds of mammals such as human,rat,mouse,naked mole rat,rabbit and cow;and the amino acid sequences showed a relatively high degree of conservation with nine particular amino acid substitutions.No significantly positive selection site was detected with Test 2 model.The expression level ofprestin mRNA in plateau zokor cochlea was significantly higher than that in plateau pika (P ＜ 0.05),and the prestin mRNA in plateau zokor cochlea was significantly higher than that in the paw and nose (P ＜ 0.01).The resuh above suggested that prestin not only is expressed in the cochlea,but also in paw,nose and tail of plateau zokor.Plateau zokors may perceive low frequency sound waves to accurately orient the space with assistance from their paws,noses and tails during their underground trunk life.