Evolution of albinism in cave planthoppers by a convergent defect in the first step of melanin biosynthesis.
Evolution of albinism in cave planthoppers by a convergent defect in the first step of melanin biosynthesis.
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DOI：
10.1111/j.1525-142x.2012.00535.x
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发表时间：
2012-03
影响因子：
2.9
通讯作者：
Jeffery WR
中科院分区：
文献类型：
--
作者：
Bilandžija H;Cetković H;Jeffery WR
白化病，黑色素的减少或损失，发现在许多不同的穴居动物。对黑色素损失的机制知之甚少。在这项研究中，我们使用的黑色素底物测定，以确定黑色素合成被阻止在独立进化的洞穴飞虱从夏威夷和克罗地亚的位置。在该测定中，将负责黑色素生物合成的酶的底物添加到体外固定的标本中，并测定其拯救黑色黑色素沉着的能力。酪氨酸，第一个底物的途径，不产生黑色素，而左旋多巴，第二个底物，恢复黑色素。底物与酶抑制剂组合用于测试途径中额外下游缺陷的可能性。结果表明，从L-DOPA和多巴胺到多巴黑色素和多巴胺黑色素这两种昆虫黑色素的下游反应是功能性的。它的结论是白化病是由缺陷的黑色素合成途径的第一步在洞穴适应的飞虱从世界上广泛分离的部分。然而，蛋白质印迹表明，酪氨酸羟化酶（TH），唯一的酶显示在昆虫的第一步，是目前在夏威夷洞穴稻飞虱。因此，一个未知的因素（S）在这一步操作可能是重要的，在进化的稻飞虱白化。在洞穴鱼Astyanaxmexicanus中，在黑色素合成的第一步也描述了遗传缺陷，这表明在洞穴适应昆虫和硬骨鱼中白化病的趋同进化。
Albinism, the reduction or loss of melanin pigment, is found in many diverse cave-dwelling animals. The mechanisms responsible for loss of melanin pigment are poorly understood. In this study we use a melanogenic substrate assay to determine the position where melanin synthesis is blocked in independently evolved cave planthoppers from Hawaii and Croatia. In this assay, substrates of enzymes responsible for melanin biosynthesis are added to fixed specimens in vitro and their ability to rescue black melanin pigmentation is determined. L-tyrosine, the first substrate in the pathway, did not produce melanin pigment, whereas L-DOPA, the second substrate, restored black pigment. Substrates in combination with enzyme inhibitors were used to test the possibility of additional downstream defects in the pathway. The results showed that downstream reactions leading from L-DOPA and dopamine to DOPA-melanin and dopaminemelanin, the two types of insect melanin, are functional. It is concluded that albinism is caused by a defect in the first step of the melanin synthesis pathway in cave-adapted planthoppers from widely separated parts of the world. However, Western blots indicated that tyrosine hydroxylase (TH), the only enzyme shown to operate at the first step in insects, is present in Hawaiian cave planthoppers. Thus, an unknown factor(s) operating at this step may be important in the evolution of planthopper albinism. In the cavefish Astyanaxmexicanus, a genetic defect has also been described at the first step of melanin synthesis suggesting convergent evolution of albinism in both cave-adapted insects and teleosts.