Hemoglobins of Kiefferulus, sister genus of Chironomus (Diptera: Insecta): evolution of the Hb VIIB cluster.

A genomic clone containing hemoglobin genes was isolated from a species of the chironomid genus Kiefferulus. Eight genes, including an apparent pseudogene, were sequenced and the amino acid sequences of the putative proteins were determined. By comparison to the previously described hemoglobins in the sister-genus Chironomus, they were identified as members of the dimeric Hb VIIB group. The results indicate that the existence of clusters of hemoglobin genes may be a common feature in chironomids and not just confined to Chironomus. The Kiefferulus genes show greatest similarity of amino acid sequence to Hb VIIB-7 from the Chironomus cluster. The results suggest that the ancestral cluster contained at least two gene types, one of which gave rise to VIIB-7 and the Kiefferulus genes while the other gave rise to the other Chironomus VIIB genes. Both clusters appear to have increased in size by duplication or unequal crossing over since the separation of the genera. It also appears that an unrelated gene present in the Chironomus cluster, Hb-Y, arose from a completely independent origin with no apparent equivalent gene anywhere in the genome of Kiefferulus or some other Chironomus species.