M、F型COⅡ基因在雌雄三角帆蚌不同发育时期的表达差异研究

Full-length cDNA cloning of M and F-type COⅡ genes and expression in different age freshwater mussel Hyriopsis cumingii

与传统的母系遗传不同,双壳贝类线粒体有M和F型2种mt DNA,称为双单亲遗传(doubly uniparental inheritance,DUI)。为了探究DUI的形成机制,实验利用RACE方法得到三角帆蚌M、F-type COⅡ基因的cDNA全长;荧光定量检测各时期各组织中M、F-type COⅡ基因的表达。结果发现,(1)M-type COⅡ基因的cDNA序列全长1244 bp,F-type COⅡ基因的cDNA序列全长808 bp,M型3′端较F型有一段546 bp的特异性延长序列;跨膜结构预测显示M-type COⅡ基因3′特异性延伸区域有4个跨膜结构,推测这段延伸序列具有一定的功能性;(2)早期幼龄(胚胎期-5月龄)三角帆蚌的组织团中,M、F-type COⅡ基因均能检测出,且同时期中F-type COⅡ基因的表达量显著高于M-type COⅡ;(3)6月龄蚌各组织中,F-type COⅡ基因在各组织中表达量明显高于M型的表达量,而M-type COⅡ基因在性腺中表达明显高于其他组织;(4)一龄雌性各组织中,M、F-type COⅡ基因均有表达;而一龄雄性各组织中,M-type COⅡ基因仅在性腺中表达;(5)二龄雌性各组织中,M、F-type COⅡ基因均有表达;二龄雄性各组织中,F-type COⅡ基因除性腺外的其他组织中均有低量表达,M-type COⅡ基因仅在性腺中表达,且表达量较高。研究表明,在三角帆蚌雌雄个体发育过程中,M-type mt DNA在组织中选择性降解或聚集。

The mitochondrial genetic patterns of bivalve mollusc are different from the traditional maternal inheritance. The mitochondria of bivalve molluscs have two kinds of mt DNA of M type and F type, which are called doubly uniparental inheritance（DUI）. In order to explore the mechanism of DUI, the full-length cDNA of M and F-type COⅡ genes in Hyriopsis cumingii was obtained by RACE. q RT-PCR was used to detect the expression of M and F-type COⅡ genes in different tissues and stages. The results are as follows： 1.The full-length cDNA sequences of M-type COⅡ gene and F-type COⅡ gene were 1244 bp and 808 bp respectively, and the 3′ end of Mtype COⅡ gene had a prolonged sequence of 546 bp. The transmembrane structure prediction showed that there were four transmembrane structures in the C-terminus extension region of the M-type COⅡ gene, suggesting that this extension sequence has certain function. 2. M-type COⅡ gene and F-type COⅡ gene were all expressed in the early juvenile（embryonic to 5-month-old） of H.cumingii, and the expression level of F-type COⅡ gene was significantly higher than that of M-type COⅡ gene. 3. In the tissues of six-month-old mussels, the expression of M-type COⅡ gene was the highest in gonads, and the expression of F-type COⅡ gene was still at a high level in the same tissues. 4. In the one-year-old female tissues, M and F-type COⅡ genes can be detected in all tissues. In male tissues, the F-type COⅡ gene was detected in each tissues, but M-type COⅡ gene was only expressed in gonads. 5. In the two-year-old female tissues, F and M type both expressed in each tissue, but the expression of Mtype COⅡ gene is very low. In the two-year-old male tissues, the F-type COII gene was detectable in addition to the gonad, and the M-type COⅡ gene was detected only in the gonad. In the two-year-old male tissues, the F-type COⅡ gene was detectable except for the gonad, and the M-type COⅡ gene was detected only in the gonad. These results suggested that M-type mt DNA is selectively degraded or aggregated in tissues during male and female development of H. cumingii.