Sequence and evolution of the gene for the monomeric globin I and its linkage to genes coding for dimeric globins in the insect Chironomus thummi

Abstract

We isolated genomic clones containing sequences encoding globins I and IA from a Chironomus thummi thummi genomic library. Three clones contain globin IA (ctt-1A) genes, while one contains a globin I (ctt-1) gene. The coding regions of the four genes are identical except for the single base substitution accounting for the globin I/IA polymorphism. The noncoding DNA flanking the coding region is more than 98% similar, confirming a previous hypothesis that the globin ctt-1 and ctt-1A genes are alleles. Hemoglobins I and IA are monomeric in the insect hemolymph. Earlier in situ hybridization studies suggested that monomeric and dimeric globin genes are clustered at different chromosomal loci. In situ hybridization of ctt-1 DNA to polytene salivary gland chromosomes places the ctt-1 gene on the same band as genes for the dimeric globins II beta and VIIB, forcing revision of the earlier hypothesis that genes for monomeric and dimeric globin genes are at different loci. The evolution of the ctt-1 and ctt-1A alleles and of the two globin gene loci are discussed.

The Globin Gene Family in Arthropods: Evolution and Functional Diversity

“…The number of HbL copies usually ranges between 1 and 4. In two cases we documented a dramatic increase in the number of HbL gene copies: (1) the non-biting midges with more than 40 HbL variants ( Kao et al, 1995 ; Trewitt et al, 1995 ; Hankeln et al, 1998 ), which are mostly considered to ensure O 2 transport in the hemolymph of the aquatic chironomid larvae ( Weber and Vinogradov, 2001 ) and (2) the branchiopod crustaceans, where Hbs are hypoxia-inducible and thus also probably relevant for respiration ( Zeis et al, 2003 ; Guadagnoli et al, 2005 ).…”

Effect of cadmium exposure on the globin protein expression in 4th instar larvae of Chironomus riparius Mg. (Diptera: Chironomidae): An ecotoxicoproteomics approach

“…In our previous study, preliminary characteriza-tion of the multiplicity of the Chironomus globin protein was conducted [25]. As with other Chironomus species [28][29][30][31][32], striking heterogeneity was observed in C. riparius Hb. The globin in C. riparius was separated into seven and six different components by nondenative PAGE and by nondenative IEF, respectively, with observed molecular weights and pIs ranging from 7 to 26 kDa and from 3.5 to 6.2, respectively.…”