| The basic helix-loop-helix(b HLH) motif is a highly conserved DNA-binding domain in proteins. Proteins containing b HLH motif comprise a transcription factor superfamily. b HLH family members are widely distributed in animals, plants, fungi and other eukaryotes. b HLH proteins play essential regulatory roles in a variety of developmental processes including cell proliferation and differentiation, neurogenesis and sex determination. b HLH motif contains approximately 60 amino acid residues and is composed of a basic(b) region and two helices separated by a variable loop(HLH) region. Animal b HLH transcription factors are divided into 45 families according to their characteristic functions. Besides, members of these 45 families are divided into higher-order group A, B, C, D, E and F respectively based on their own structural characteristics and features of their target DNA elements.The jewel wasp, Nasonia vitripennis(Hymenoptera: Pteromalidae), belongs to a genus of small pteromalid parasitoid wasps. Jewel wasps are not only important natural enemy resources, but also an important model organism of hymenoptera insects particularly for complex trait analysis, developmental genetics, and evolutionary genetics. To know what b HLH family members the jewel wasp has are helpful to future studies aiming to reveal specific developmental and physiological features in the jewel wasp. In this study, we used BLAST searches, multiple sequence alignment and phylogenetic analysis to conduct comprehensive identification and classification of the b HLHfamily members in jewel wasp. The major results obtained are as follows:1. 48 putative b HLH genes were identified in the genome of jewel wasp, Nasonia vitripennis. Based on phylogenetic analyses, all 48 jewel wasp b HLH genes were classified into 36 evolutionary distinct families and 6 higher-order groups. 19, 12, 9, 1, 6, and 1 jewel wasp b HLH genes were assigned to the A, B, C, D, E and F groups, respectively.2. We searched jewel wasp protein databases and found that, among all of the identified 48 jewel wasp b HLH family members, 21 proteins were annotated in consistence with our analytical result, 17 proteins were annotated in difference with our analytical result, 8 proteins were merely annotated as hypothetical proteins, and protein accession numbers for two Nvb HLH motifs are currently unavailable. Therefore, our current work provides useful information for further characterization and annotation of 27 jewel wasp protein sequences.3. A close comparison of the distribution of b HLH members in different families with other insect species reveals that jewel wasp does not have b HLH members in families Net, Myo Ra and PTFa, while other 10 insect species all have one or even two members. Whether the absence of specific b HLH family members in the jewel wasp has any relationship with its unique developmental feature at the larval stage requires further analysis.4. Structural information of 29 N. vitripennis b HLH genes was obtained through in silico cloning, among which the structures of 19 b HLH genes are relatively complete, mainly because there exists a transcription start site but no poly(A) tail. Structures of the rest 10 b HLH genes are incomplete, mainly each of them has neither a transcription start site nor a poly(A) tail.The achievements of this study not only provide useful background information for future studies on regulatory mechanisms of jewel wasp b HLH transcription factors on growth and development, but also facilitate further comparative studies on b HLH gene structures and functions between various insect species. |
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