Molecular Cloning and the Expression Profile of Vitellogenin in Relation to Tissue and Food Source inApolygus lucorum(Hemiptera: Miridae)

Abstract

Vitellogenin proteins (Vgs) are precursors of the major egg yolk proteins in many oviparous vertebrates and invertebrates. Here we cloned the full-length cDNA of the Vg gene of Apolygus lucorum , an omnivorous mirid bug that feeds on various agricultural crops and small insects. The gene has 6,131 base pairs (bp) with an open reading frame (ORF) of 5,988 bp, encoding a protein with 1,996 amino acids, with molecular mass 218.3 kDa and isoelectric point 9.02. Phylogenetic analysis showed that Vg gene has a high similarity with that in Hemiptera insects and was most closely related to the rice leaf bug, Trigonotylus caelestialium . The expression of Vg gene was significantly higher in the fat body than in other tissues in females (ovary, hemolymph, gut, and malpighian tubule). Vg gene expression was extremely low in newly emerged adult females and increased with age. The effect of different food sources on the expression level of Vg in adult females was investigated after they were fed on green bean pods (Gb), H. armigera eggs (He), or a combination of green bean pods and H. armigera eggs (GbHe). The results showed that transcript level of Vg gene in females was significantly higher on the GbHe diet than on Gb or He. Our results demonstrate that A. lucorum can acquire nutrients from both plant and animal origin food sources, and the combined food sources significantly facilitated Vg synthesis.