Abstract:

Objective To identify the yellow family genes in Aedes aegypti and analyze the gene structure, phylogenetic evolution and their expression at various developmental stages and in different tissues. Methods The yellow gene family was identified in Ae. aegypti by blasting the Ae. aegypti genome database with the amino acid sequence of the MRJP domain of Dm-yellow gene of Drosophila melanogaster（GenBank No. AAF45497）. The physico-chemical property and domains were analyzed with the on-line ExPaSy software. The signal peptide was predicted using SignalP4.1 software. Sequence alignment and the phylogenetic tree were made through combined use of DNAstar, MEGA6.0 and GeneDoc. Total RNA was extracted from Ae. aegypti, cDNA was generated, and expression of the yellow family genes at various developmental stages （egg, first to fourth instar, pupa, non-blood-fed female and male mosquitoes） and in different tissues （salivary gland, midgut, fat body, and ovary） was quantified using qRT-PCR. Results Twelve yellow genes were identified from Ae. aegypti genome: Aa-yellow, Aa-yellow-b, Aa-yellow-c, Aa-yellow-d, Aa-yellow-e, Aa-yellow-f2, Aa-yellow-fb, Aa-yellow-fc, Aa-yellow-g, Aa-yellow-g2, Aa-yellow-h, and Aa-yellow-x. Bioinformatics demonstrated that all covered the MRJP domain and a signal peptide sequence. Sequence alignment revealed low （15%-49%） homology among the proteins, but high homology（60%） in the conserved domain. According to the phylogenetic tree analysis, the encoded 12 YELLOW proteins were classified into 5 subfamilies, and 11 had orthologues in D. melanogaster. qRT-PCR revealed high expression of Aa-yellow-d （0.018 9） and Aa-yellow-x （0.023 5） in male Ae. aegypti （P<0.01 or P<0.05）; high expression of Aa-yellow-fc （0.024 8, 0.034 9） in female Ae. aegypti and in the salivary gland （P<0.01）; high expression of Aa-yellow-f2 （0.093 4） in the second instar stage （P<0.01）; high expression of Aa-yellow （0.562 1）, Aa-yellow-e （0.004 4）, and Aa-yellow-fb （0.008 4） in the third instar stage （P<0.05）; and high expression of Aa-yellow （0.569 4）, Aa-yellow-e （0.027 0）, Aa-yellow-f2 （0.006 5）, Aa-yellow-fb （0.001 0）, Aa-yellow-h （0.084 8） and Aa-yellow-x （0.015 1） in the ovary. Genes other than Aa-yellow-c （0.004 0） and Aa-yellow-x （0.007 4） were hardly expressed in the midgut. Conclusion The 12 yellow genes identified in the Ae. aegypti genome have low homology, and are differentially expressed at different developmental stages and in tissues.

Key words: Aedes aegypti, yellow gene family, qRT-PCR, Expression profile