A genome-wide survey and analysis of basic helix-loop-helix genes in the Asian citrus psyllid, Diaphorina citri (Hemiptera: Psyllidae)

The basic helix-loop-helix (bHLH) proteins are important player in regulation of various eukaryotic developmental processes such as neurogenesis, myogenesis and heart morphogenesis. The Asian citrus psyllid (Diaphorina citri) is a sap-sucking pest which is widely distributed in southern Asia and causes greening disease in citrus orchard. In this study, Diaphorina citri genome is found to encode 52 bHLH genes. Through in-depth phylogenetic analyses, all 52 Diaphorina citri bHLH (DcbHLH) genes are classified into correspondent bHLH families according to their orthology with bHLHs from fruit fly and other insect species. Examination of GenBank annotations of these 52 DcbHLH members indicated that annotations of only 21 DcbHLH proteins are consistent with our analysis. Therefore, our data provide useful information for updating annotations to other 31 DcbHLH proteins. Among the 52 DcbHLH proteins, DcClk, DcSima, DcCyc and DcCwo have dual HLH motifs, which have not been found in any other bHLH proteins. Diaphorina citri has 2, 3 and 2 bHLH members respectively in Net, Hand and SRC families while other insect species have only one member in these families. The existence of more Net, Hand and SRC family members probably means that Asian citrus psyllid possesses more complex regulatory network in controlling intervein emergence, heart morphogenesis and larval metamorphosis than other insects. These results provide a solid basis and interesting aspects for further investigations into the evolution and functions of bHLH genes in Diaphorina citri.