title: Molecular characterization and gene expression of apolipophorin III from the ghost moth, Thitarodes pui (Lepidoptera, Hepialidae).
abstract: Apolipophorin III (apoLp-III) functions in lipid transport and immune activation in insects. We cloned a cDNA encoding putative apoLp-III from larvae of Thitarodes pui, a host species of Ophiocordyceps sinensis, with great economic importance in the Tibetan Plateau. Excluding a putative signal peptide of the first 20 amino acid residues, the 171-residue mature apoLp-III has a calculated molecular mass of 18,606 Da. T. pui apoLp-III shares little sequence homologies (<36%) with other apoLp-IIIs. Phylogenetic analysis reveals that T. pui apoLp-III belongs to a distinct, early diverging lineage of lepidopteran apoLp-IIIs. Homology modeling of T. pui apoLp-III shows a bundle of five amphipathic α-helices, including a short helix 3'. T. pui apoLp-III was constitutively expressed in larval fat body at lower levels than pupal and adult fat body. Significant induction of apoLp-III expression, associated with strongest nodulation response, was observed in both sixth and eighth instar larvae challenged with Beauveria bassiana conidia at 1 hr after inoculation, compared with saline-injected controls. The inoculation experiment as well as previous field studies revealed the relative susceptibility of the sixth instar to the entomopathogenic fungus. ApoLp-III transcripts in the infected sixth and eighth instars were found to be induced highest 2- and 14.7-fold, respectively, during the first 12 hr. In late-stage infection, the infected susceptible sixth instar showed decrease in apoLp-III expression followed by production of B. bassiana hyphal bodies, whereas the infected eighth instar showed longer lasting increase in the expression. These results suggest that apoLp-III might contribute to T. pui immune response against fungal pathogens.
authors: State Key Laboratory for Biological Control/Institute of Entomology, Sun Yat-Sen University, Guangzhou, People' Republic of China.
authors: Zixuan
authors: Z
authors: Sun
authors: Junfeng
authors: J
authors: Yu
authors: Wenjing
authors: W
authors: Wu
authors: Guren
authors: G
authors: Zhang
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001053:Apolipoproteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D052982:Beauveria / Q000276:immunology; D019476:Insect Proteins / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D007814:Larva / Q000276:immunology / Q000378:metabolism; D008297:Male; D008969:Molecular Sequence Data; D009036:Moths / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D040681:Structural Homology, Protein
chemical_list: D001053:Apolipoproteins; D019476:Insect Proteins; C042470:apolipophorin III