Abstract: Aquaporin (AQP) is a vital transmembrane protein participated in water recycling, desiccation resistance and cold hardiness in insects through the transportation of some neutral small molecules. In order to research the molecular characterization and spatial and temporal expression of AQP genes in Spodoptera litura, two full-length transcript variants of aquaporin 1 (AQP1) gene were cloned from S. litura by RT-PCR and RACE technology and named SL-AQP1A (GenBank accession number: KC999953) and SL-AQP1B (GenBank accession number: KC999954), respectively. There is a continuous 81 bp deletion in the 5′ open reading frame tail end of SL-AQP1B compared to that of SL-AQP1A; other sections of the sequences, however, are the same between the two genes. The deduced amino acid sequences of SL-AQP1A and SL-AQP1B are highly conserved among Lepidoptera species. Both of the two proteins have six full transmembrane domains, two semi-transmembrane domains, two conservative NPA (asparagine-proline-alanine) motifs, and the ar/R (aromatic arginine) selectivity filter based on topology and three dimensional predictions. Real time quantitative PCR results showed that there were obvious differences in the overall expression level of SL-AQP1 in the detected samples, and  moreover SL-AQP1B had a higher relative expression level than SL-AQP1A. SL-AQP1 was expressed at high levels in the egg and pre-pupal stages, and in such tissues as the hemolymph, midgut, Malpighian tubules and salivary glands, suggesting that SL-AQP1 play key roles in the osmoregulation and embryonic development and metamorphosis of S. litura. The results provide some molecular proofs for the physiological effect of SL-AQP1 in S. litura.

Key words: Spodoptera litura, aquaporin, gene cloning, transcript variant, molecular characterization, expression analysis