BRISCOE, AD; SISON-MANGUS, MP; Univ. of California, Irvine: Blue Opsin Genes for Blue Butterflies

Physiological study has shown that butterflies belonging to the Lycaenidae or the �blues� have 4 spectral types of visual pigments (Bernard and Remington 1991). In this study, we characterized these visual pigments molecularly. A cDNA library from the eyes of 2 male Lycaena rubidus was constructed, and screened for opsin transcripts using 3� RACE (rapid amplification of cDNA ends), cloning, and automated sequencing. Four distinct opsin transcripts were detected with varying fragment sizes of 781, 782, 677 and 890 bp, and which encode protein fragments of 120, 118, 121 and 120 amino acids, respectively. These fragments span cytoplasmic loop V, transmembrane domains VI and VII through the C-terminus. Phylogenetic analysis indicated that these 4 opsin transcripts cluster within clades of UV-, blue- and long wavelength (LW) -sensitive insect opsins. Unexpectedly, we found that L. rubidus contains duplicated blue-sensitive opsin genes. To our knowledge, this is the first report of gene duplication of the blue-sensitive opsin among insects. Preliminary bootstrap analysis revealed that the lycaenid UV and blue opsins are most closely related to that of their nymphalid Vanessa cardui homologues. Several amino acid substitutions (ca. 16%) and indels were detected between the 2 blue opsins after aligning their sequences manually. The putative function of these duplicated blue opsin genes in lycaenids is discussed.