Abstract:  【Aim】 To study the function of chemosensory proteins (CSPs) in the western flower thrips,  Frankliniella occidentalis . 【Methods】 A CSP gene from  F.occidentalis was cloned using RT-PCR and RACE-PCR strategies. Nucleotide sequence was analysed using DNAMAN software. Homology was analysed using BLAST. A neighbor-joining tree was constructed using MEGA6. Expression profiles of  FoccCSP-1 in different developmental stages and different tissues of adults (antennae, head, legs, thorax and abdomen) were assayed using real-time quantitative PCR (qRT-PCR). Polyclonal antisera were prepared by immunizing New Zealand white rabbits with purified protein, and reacted with this protein in slices and 10 nm colloidal gold-affinipure goat anti-rabbit IgG. The immunolocalization of FoccCSP1 protein in adult tissues was clarified by transmission electron microscope. 【Results】 A new chemosensory protein gene was cloned and identified from  F. occidentalis  and named  FoccCSP-1 (GenBank accession number: KM527949).  FoccCSP 1 cDNA contains a 288 bp openreading frame encoding a putative protein of 95 amino acids with the molecular mass of 11.377 kD and the isoelectric point of 4.72. The deduced amino acid sequence contains the typical four-cysteine signature like CSPs from other insects. FoccCSP1 shows the highest amino acid sequence identity and the closest evolutionary relationship with LmigCSP (GenBank accession number: CAJ01476.1) of Locusta migratoria.  FoccCSP-1 was predominantly expressed in 1-day-old female adults and the 2nd instar nymphae, and also highly expressed in antennae and legs. The recombinant expressed plasmid pET-30a/ FoccCSP 1 was successfully constructed, and the recombinant protein was expressed in a prokaryotic expression system and purified by affinity chromatography using Ni-NTA-Sefinose Column. The immunocytochemistry results indicated that the lymph of antennae, legs and head was strongly labeled by anti FoccCSP1 antisera. 【Conclusion】 The sequence characteristics of nucleotides and amino acids of  FoccCSP 1 were clarified.  FoccCSP 1 is broadly expressed in multiple developmental stages and adult tissues, suggesting that FoccCSP1 might play an important role in olfactory reception, chemosensory and development regulation of F.occidentalis.

Key words: Frankliniella occidentalis, chemosensory protein, molecular cloning, prokaryotic expression, expression profile, immunolocalization