Cloning of Odorant Binding Protein Gene in Lymantria dispar and Its Response to CO₂ Stress

Odorant binding proteins(OBPs) can specifically bind and transport odor molecules, which play an important role in sensing odorants in insect olfactory system. The characteristics of the OBP gene in Lymantria dispar and its response to elevated CO₂ concentration were studied in order to provide a theoretical basis for clarifying the olfactory response mechanism of the L. dispar under global climate change. Two OBP genes in L. dispar were cloned and its characteristics were analyzed by bioinformatics. Tissue specific expressions of OBP genes were determined under different CO₂ concentrations by qRT-PCR. The results showed that the open reading frame(ORF) length of LdOBP1 and LdOBP2 genes are 450 bp and 417 bp, which are encoding 149 and 138 amino acids, respectively. The molecular mass of the protein is 19.41 kDa and 15.35 kDa, and the theoretical isoelectric points are 11.17 and 6.73 for LdOBP1 and LdOBP2, respectively. The LdOBP1 is alkaline protein and LdOBP2 is acidic protein. Both LdOBP1 and LdOBP2 have no obvious transmembrane region. LdOBP1 has no signal peptide sequence while LdOBP2 has signal peptide sequence from 1–22. Phylogenetic tree analysis showed that LdOBP1 and LdOBP2 in L. dispar are closely related to the OBP(AYD42195.1) and OBP(AYD42180.1) in Carposina sasakii, respectively. The OBPs genes in the L. dispar larvae had the highest expression levels in the head. High concentration of CO₂ significantly inhibited the expression of LdOBP1 genes in the L. dispar tissues, while LdOBP2 gene expressions were induced in the head and midgut. The OBP genes in L. dispar have the highest expression levels in adult antennae. The expression of LdOBP1 and LdOBP2 genes were significantly inhibited in the antennae of L. dispar adult under high concentration of CO₂ stesses. L. dispar may be respond to CO₂ stress by regulating the expression level of OBP genes in various tissues.