Evolution of color vision in pierid butterflies: blue opsin duplication, ommatidial heterogeneity and eye regionalization in Colias erate

摘要

This paper documents the molecular organiza?tion of the eye of the Eastern Pale Clouded Yellow but?terfly, Colias erate (Pieridae). We cloned four cDNAs encoding visual pigment opsins, corresponding to one ultra?violet, two blue and one long wavelength-absorbing visual pigments. Duplication of the blue visual pigment class occurs also in another pierid species, Pieris rapae, suggest?ing that blue duplication is a general feature in the family Pieridae. We localized the opsin mRNAs in the Colias ret?ina by in situ hybridization. Among the nine photoreceptor cells in an ommatidium, R1-9, we found that R3-8 expressed the long wavelength class mRNA in all omma?tidia. R1 and R2 expressed mRNAs of the short wavelength opsins in three fixed combinations, corresponding to three types of ommatidia. While the duplicated blue opsins in Pieris are separately expressed in two subsets of R1-2 pho?toreceptors, one blue sensitive and another violet sensitive, those of Colias appear to be always coexpressed.