Flachsbarth S, Kruse M, Burmester T
Institute of Zoology, University of Hamburg, Hamburg, Germany.
Insect Mol Biol. 2017 Oct;26(5):633-641. doi: 10.1111/imb.12323. Epub 2017 Jun 21.
Haemocyanin is the copper-containing respiratory protein present in many arthropods. In the hexapods, respiratory proteins had long been considered unnecessary as sufficient O was thought to be obtained via the trachea. Nevertheless, many ametabolous and hemimetabolous hexapod species actually possess haemocyanin. Here we investigated the occurrence of haemocyanin in Collembola (springtails). Haemocyanin was found in 22 collembolan species of the suborders Symphypleona, Tomoceroidea and Entomobryomorpha, demonstrating its widespread occurrence. No haemocyanin was identified in 16 species of these taxa, and it appears to be absent in Poduromorpha. The presence of haemocyanin does not correlate with either the phylogenetic history or lifestyle of the investigated species. We further investigated the function of haemocyanin in Folsomia candida (Entomobryomorpha) by applying different hypoxia regimes. Whereas short-term (1 h) and mild (10% O ) hypoxia led to a decrease in haemocyanin mRNA, strong hypoxia (24 h, 1.5% O ) resulted in a ∼4300-fold increase in haemocyanin expression. Hypoxia induction of haemocyanin could not be demonstrated in evolutionarily more advanced Hexapoda, where it is restricted to the embryo. The results indicate (1) an important role of haemocyanin in the oxygen supply of F. candida, which may be adaptive in the potentially hypoxic environment in the soil, and (2) a change in haemocyanin function in hexapod evolution.
血蓝蛋白是一种存在于许多节肢动物体内的含铜呼吸蛋白。在六足动物中，由于人们认为通过气管就能获取足够的氧气，长期以来呼吸蛋白一直被认为是不必要的。然而，许多无变态和不完全变态的六足动物物种实际上都拥有血蓝蛋白。在此，我们研究了弹尾目（跳虫）血蓝蛋白的存在情况。在愈腹亚目、圆跳虫总科和长角跳虫亚目的22种弹尾虫中发现了血蓝蛋白，这表明其广泛存在。在这些类群的16个物种中未鉴定出血蓝蛋白，并且在原尾亚目中似乎不存在血蓝蛋白。血蓝蛋白的存在与所研究物种的系统发育历史或生活方式均无关联。我们通过应用不同的低氧条件，进一步研究了血蓝蛋白在白符跳（长角跳虫亚目）中的功能。短期（1小时）和轻度（10%氧气浓度）低氧导致血蓝蛋白mRNA水平下降，而强烈低氧（24小时，1.5%氧气浓度）则导致血蓝蛋白表达增加约4300倍。在进化上更为高等的六足动物中，低氧诱导血蓝蛋白的现象无法得到证实，在这些动物中血蓝蛋白仅限于胚胎期存在。结果表明：（1）血蓝蛋白在白符跳的氧气供应中具有重要作用，这在土壤中潜在的低氧环境中可能具有适应性；（2）六足动物进化过程中血蓝蛋白功能发生了变化。
