Regional evolution of venom-gland phospholipase A2 isoenzymes of Trimeresurus flavoviridis snakes in the southwestern islands of Japan
Regional evolution of venom-gland phospholipase A2 isoenzymes of Trimeresurus flavoviridis snakes in the southwestern islands of Japan
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DOI：
10.1042/0264-6021:3470491
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发表时间：
2000-04-15
影响因子：
4.1
通讯作者：
Ohno, M
中科院分区：
文献类型：
--
作者：
Chijiwa, T;Deshimaru, M;Ohno, M
常规层析分析表明，冲绳岛黄花蛇蛇毒的磷脂酶A(2)(PLA2)同工酶的组成与大岛岛和德岛岛黄花蛇毒的组成有很大的不同。最显著的特征是，在Amami-Oshima和Tokunoshima T.flavviridis的毒液中大量表达的肌毒性[Lys(49)]plA(2)同工酶，称为BPI和BPII，在冲绳T.flavviridis的毒液中缺失。Northern印迹分析表明，BPI和BPII基因的表达缺失。用单链构象多态-聚合酶链式反应(SSCP)方法对3个岛的黄绿假单胞菌毒腺基因进行分析，并与5种编码不同磷脂酶A(2)同工酶的DNA进行比较，结果也表明BPI和BPII基因在冲绳黄绿色锥虫毒腺中不表达。相反，用多种探针进行基因组Southern杂交分析表明，只有BPI和/或BPII基因的上游和下游区域对应的条带才能在冲绳黄褐斑潜蝇中检测到。这些结果表明，冲绳黄褐飞虱基因组中BPI和BPII基因已经失活，形成假基因。不同于Amami-Oshima和Tokunoshima T.flvoviddis基因组DNA，冲绳黄曲霉基因组DNA的BPI和BPII基因片段在第二外显子的5‘部分和第二内含子的中间部分不能被PCR扩增。在序列分析中，分别位于第一外显子和第三外显子的两个涉及BPI和BPII基因多态的片段在冲绳黄褐飞虱基因组假基因的多态位置上只检测到一个碱基。基于这些事实，对于假基因来说，很明显，BPI基因的上游区域直到第二外显子的5‘端，而BPII基因的下游区域从第二内含子的中间开始，是一种连锁的形式，可能存在插入。这些观察表明，分离了一两百万年的黄绿色锥虫毒腺中的磷脂酶A(2)同工酶基因已经独立进化。它们的进化是地区性的，从几个方面考虑和观察，似乎是适应环境的。
Conventional chromatographic analysis showed that phospholipase A(2) (PLA(2)) isoenzymes of the venom of Trimeresurus flavoiridis (Habu snake) of Okinawa island are profoundly different in composition from those of T. flavoviridis of Amami-Oshima and Tokunoshima islands. The most striking feature was that myotoxic [Lys(49)]PLA(2) isoenzymes, called BPI and BPII, which are expressed abundantly in the venoms of Amami-Oshima and Tokunoshima T. flavoviridis, are missing from the venom of Okinawa T. flavoviridis. Northern blot analysis of Okinawa T. flavoviridis venom-gland mRNA species showed the absence of BPI and BPII mRNA species. Analysis by single-stranded conformational polymorphism-PCR of venom-gland mRNA species of T. flavoviridis from three islands, with reference to five DNA species each encoding different PLA(2) isoenzymes from Tokunoshima T. flavoviridis venom gland, also suggested that BPI and BPII mRNA species are not expressed in Okinawa T. flavoviridis venom gland. In contrast, genomic Southern blot analysis with a variety of probes showed that only the bands corresponding to the upstream and downstream regions of the genes for BPI and/or BPII can be detected in Okinawa T. flavoviridis. These results suggested that the genes for BPI and BPII in Okinawa T. flavoviridis genome had been inactivated to form pseudogenes. Differently from Amami-Oshima and Tokunoshima T. flavovirdis genomic DNAs, PCR amplification of the segments of BPI and BPII genes between the 5' moiety of second exon and the middle portion of second intron failed for Okinawa T. flavoviridis genomic DNAs. In sequence analysis of the two segments involving polymorphism between BPI and BPII genes, which are located in first exon and third exon, respectively, only one base was detected at the polymorphic positions for pseudogene in Okinawa T. flavoviridis genome. Based on these facts, it became evident for pseudogene that the upstream region of BPI gene down to the 5' moiety of second exon and the downstream region of BPII gene starting from the middle portion of second intron are in a linked form with a possible insertion. Such observations suggest that venom-gland genes for PLA(2) isoenzymes in T. flavoviridis snakes isolated for one to two million years have evolved independently. Their evolution is regional and seems, from several lines of consideration and observation, to be adaptive to the environment.