tailieunhanh - Báo cáo khoa học: The occurrence of hemocyanin in Hexapoda

Hemocyanins are copper-containing, respiratory proteins that have been thoroughly studied in various arthropod subphyla. Specific O2 -transport proteins have long been considered unnecessary in Hexapoda (including Insecta), which acquire O2 via an elaborate tracheal system. | The occurrence of hemocyanin in Hexapoda Christian Pick Marco Schneuer and Thorsten Burmester Institute of Zoology and ZoologicalMuseum University of Hamburg Germany Keywords evolution hemocyanin hexamerin insect oxygen Correspondence T. Burmester Institute of Zoology and ZoologicalMuseum University of Hamburg Martin-Luther-King-Platz 3 D-20146 Hamburg Germany Fax 49 40 42838 3937 Tel 49 40 42838 3913 E-mail Database The nucleotide sequences reported in this paper have been submitted to the EMBL GenBank databases under the accession numbers FM242638 to FM242654 Received 15 October 2008 revised 5 January 2009 accepted 21 January 2009 doi Hemocyanins are copper-containing respiratory proteins that have been thoroughly studied in various arthropod subphyla. Specific O2-transport proteins have long been considered unnecessary in Hexapoda including Insecta which acquire O2 via an elaborate tracheal system. However we recently identified a functional hemocyanin in the stonefly Perla marginata Plecoptera and in the firebrat Thermobia domestica Zygentoma . We used RT-PCR and RACE experiments to study the presence of hemocyanin in a broad range of ametabolous and hemimetabolous hexapod taxa. We obtained a total of 12 full-length and 5 partial cDNA sequences of hemocyanins from representatives of Collembola Archeognatha Dermaptera Orthoptera Phasmatodea Mantodea Isoptera and Blattaria. No hemocyanin could be identified in Protura Diplura Ephemeroptera Odonata or in the Eumetabola Holometabola Hemiptera . It is not currently known why hemocyanin has been lost in some taxa. Hexapod hemocyanins usually consist of two distinct subunit types. Whereas type 1 subunits may represent the central building block type 2 subunits may be absent in some species. Phylogenetic analyses support the Pancrustacea hypothesis and show that type 1 and type 2 subunits diverged before the emergence of the Hexa-poda. The copperless .