Molecular Characteristics of Fat Body Protein 1 in the Oriental Fruit Fly, Bactrocera dorsalis

Abstract

Bactrocera dorsails fat body protein 1 (Bdfbp1) cDNA was cloned (GenBank accession no. MT514270), and the complete 3,749-bp cDNA encoded a 1,152-amino acid protein. The phylogenetic relationship of dipteran fbp1s was analyzed. The sequence XP_028900815 from the insect genome project for Zeugodacus cucurbitae (LOC105219342) was proposed that two fbp1 genes were present in the sequence. The developmental transcriptional expression profiles were determined. In the larval stages, Bdfbp1 mRNA had significantly higher expression in the late third instar larvae compared with first, second, and early third instar larvae. In the pupal stages, the highest expression of Bdfbp1 mRNA was found in the newly pupated pupae and then decreased with age. In the fat body of female adults, Bdfbp1 was highly expressed in newly emerged samples and decreased rapidly over the following three days. In the fat body of male adults, Bdfbp1 was highly expressed in newly eclosed samples. RNAi treatment decreased the expression level of Bdfbp1 without statistical difference. However, RNAi treatment significantly decreased the rate of eclosion. These results suggest that Bdfbp1 may function as a storage protein and be associated with adult eclosion.

Keywords: Bactrocera dorsalis; eclosion; fat body protein 1; transcriptional expression.

Figure 1

Assembly of the fragments of the fbp1 cDNA cloning in B. dorsalis.

Figure 2

Deduced amino acid sequences of the fat body protein 1 cDNA from B. dorsalis (GenBank accession number MT514270). The cleavage site of the putative signal peptide sequence is indicated by a vertical arrow. The hemocyanin N domain is underlined, the hemocyanin C domain is indicated with double underlines, and the high molecular weight glutenin subunit is marked in gray.

Figure 3

Alignment between Bdfbp1 MT514207 (amino acid sequence 421–594) and Bdfpb1 XP029405180 (amino acid sequence 421–660) shows that MT514207 is 66 amino acids shorter than XP029405180.

Figure 4

The phylogenetic tree of 11 versions of insect fat body protein 1 (fbp1) was constructed by neighbor joining. Numbers at nodes are based on bootstrapping statistical support. Scale bar = 0.1 substitution/site. Conserved domains in parentheses are preceded by the scientific name, and the accession number. N: hemocyanin N; M: hemocyanin M; C: hemocyanin C; ghmw: high molecular weight glutenin subunit.

Figure 5

Developmental profiles of Bdfbp1 transcription were determined through qPCR. (a) larval stage: first, second, early third, and late third instar; (b) pupal stage: 0–8 days after pupation; (c) adult female fat body, and (d) adult male fat body: 0–10 days after eclosion. Statistical analyses using ANOVA followed by a Tukey multiple comparison test were performed to identify differences between individual means. The same letters indicate no significant difference (p > 0.05). Standard deviation of three independent biological replicates is indicated by error bars in (a–d).

Figure 6

(a) The eclosion rate of B. dorsalis after RNAi treatment of larvae; (b) Bdfbp1 relative transcriptional expression in B. dorsalis late third instar larvae after RNAi treatment. Statistical analyses were performed using Student’s t test. The asterisk indicates significant difference (p < 0.05). The standard deviation of each triplicate is shown by error bars in (a,b).