Kasinsky H E, Gutovich L, Kulak D, Mackay M, Green D M, Hunt J, Ausio J
Department of Zoology, University of British Columbia, Vancouver, Canada.
J Exp Zool. 1999 Dec 1;284(7):717-28.
Sperm nuclear basic proteins (SNBPs) that condense chromatin are very diverse. In animals, evolution of SNBPs has proceeded from lysine-rich histone H type in sponges to more arginine-rich protamine-like PL and protamine P types. Yet sporadic PL/P to H reversions are known to occur in both protostomes and deuterostomes. To determine why this is the case, we have examined SNBPs in eleven anuran species. We find that sperm of the primitive, internally fertilizing archeobatrachian frog A. truei (family Ascaphidae) has PL/P type (42 mol % arginine), with an electrophoretic profile similar to SNBPs in another archeobatrachian, externally fertilizing Leiopelma hochstetteri (family Leiopelmatidae). Cytochemistry of sperm nuclei in the advanced, externally fertilizing neobatrachian frogs Crinia signifera and C. deserticola (family Myobatrachidae) indicates that they have reverted to H type SNBPs. This is also known to be the case in externally fertilizing Rana (family Ranidae) and Silurana, a subgenus of Xenopus (family Pipidae). Such a trend, from PL/P type SNBPs in two archeobatrachians to sporadic reversions to H type in more advanced frogs, parallels the ultrastructural simplification from complex A. truei introsperm to neobatrachian aquasperm that Jamieson et al. (1993. Herpetologica 49:52-65) attribute as a secondary reversion to external fertilization.
使染色质凝聚的精子核碱性蛋白（SNBPs）种类繁多。在动物中，SNBPs的进化过程是从海绵中富含赖氨酸的组蛋白H型，发展到富含精氨酸的鱼精蛋白样PL型和鱼精蛋白P型。然而，已知在原口动物和后口动物中都发生过从PL/P型到H型的零星逆转。为了确定为何会出现这种情况，我们研究了11种无尾目物种的SNBPs。我们发现，原始的体内受精古蛙科蛙类阿氏尾蟾（阿氏尾蟾科）的精子具有PL/P型（42摩尔%精氨酸），其电泳图谱与另一种体外受精的古蛙科蛙类霍氏滑跖蟾（滑跖蟾科）的SNBPs相似。在进化程度较高的体外受精新蛙亚目蛙类长趾姬蛙和荒漠姬蛙（姬蛙科）中，精子细胞核的细胞化学分析表明它们已逆转回H型SNBPs。在体外受精的蛙属（蛙科）和非洲爪蟾亚属（非洲爪蟾科）中也已知是这种情况。这样一种趋势，从两种古蛙科蛙类的PL/P型SNBPs到更高级蛙类中零星逆转回H型，与Jamieson等人（1993年。《爬虫学》49:52 - 65）所认为的从复杂的阿氏尾蟾内向精子到新蛙亚目水精子的超微结构简化相平行，他们将这种简化归因于向体外受精的二次逆转。
