Adult stemmata of the butterfly Vanessa cardui express UV and green opsin mRNAs.

Department of Ecology and Evolutionary Biology, Comparative and Evolutionary Physiology Group, University of California, 321 Steinhaus Hall, Irvine, CA 92697, USA.
Cell and Tissue Research (Impact Factor: 3.33). 02/2005; 319(1):175-9. DOI: 10.1007/s00441-004-0994-3
Source: PubMed

ABSTRACT Adult stemmata are distinctive insect photoreceptors located on the posterior surfaces of the optic lobes. They originate as larval eyes that migrate inward during metamorphosis. We used a combination of light microscopy and in situ hybridization to examine their anatomical organization in the butterfly Vanessa cardui and to test for the presence of visual pigments, the light sensitive components of the visual transduction pathway. The bilateral cluster of six internal stemmata is located near the ventral edge of the lamina. They retain the dark screening pigment and overlying crystalline cones of the larval stemmata. We found two opsin mRNAs expressed in the stemmata that are also expressed, respectively, in UV-sensitive and green-sensitive photoreceptor cells in the compound eye. A third mRNA that is expressed in blue-sensitive photoreceptor cells of the compound eye was not expressed in the stemmata. Our results reinforce the idea that the adult stemmata are not merely developmental remnants of larval eyes, but remain functional, possibly as components of the circadian input channel.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Spectral tuning of rhodopsins commonly refers to the effects of opsin amino acid substitutions on the wavelength for peak sensitivity of the rhodopsin absorption spectrum. Nymphalini butterflies provide an opportunity for identifying some of the amino acid substitutions responsible for insect rhodopsin spectral tuning because the majority of photoreceptor cells (R3-9) in the adult retina express only a single long wavelength-sensitive (LWS) opsin mRNA transcript. Therefore, the opsin genotype can be directly correlated with its phenotype. We determined the LWS opsin gene sequence from cDNA of the mourning cloak Nymphalis antiopa, and from genomic DNA of the malachite Siproeta stelenes and the peacock Inachis io. Using an epi-microspectrophotometer we examined each butterfly's eyeshine for photochemical evidence of multiple LWS rhodopsins and found only one. We then performed partial-bleaching experiments to obtain absorbance spectra for the LWS rhodopsins of all three species as well as from another nymphalid, the buckeye Junonia coenia. The isolated LWS opsin gene sequences varied in length from 1437-1612 bp and encode rhodopsins R522 (S. stelenes), R530 (I. io), R534 (N. antiopa) and, together with a previously published sequence, R510 (J. coenia). Comparative sequence analysis indicates that the S. stelenes rhodopsin is slightly blue-shifted compared to the typical 530 nm lepidopteran rhodopsin because of the presence of a S138A substitution at a homologous site that in mammalian MWS/LWS rhodopsins causes a 5 nm blue-shift. The difference in peak absorption between R522 of S. stelenes and R530 of Inachis io is therefore largely accounted for by this substitution. This suggests that spectral tuning mechanisms employing the S138A may have evolved in parallel in mammalian and butterfly MWS/LWS rhodopsins across 500 million years of evolution.
    Journal of Experimental Biology 03/2005; 208(Pt 4):687-96. · 3.00 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Composed of a chromophore bound to an integral membrane protein (opsin), visual pigments are phenotypically characterized by the wavelength of maximal absorption (ëmax). The underlying molecular mechanism controlling ëmax is the interaction between the opsin amino acid sequence and the chromophore. While a plethora of studies have looked at structure/function relationships in vertebrate opsins, fewer studies have investigated similar issues in invertebrates. Furthermore, those few studies undertaken in invertebrate systems suggest different mechanisms of spectral tuning and photoactivation compared to vertebrate systems. This dissertation research is focused on expanding our knowledge of opsin evolution in invertebrate systems, particularly from non-insect taxa. First, issues related to opsin evolution and the maintenance of supposedly 'non-functional' genes were explored in a review of regressive and reverse evolution. Second, in order to place studies of crustacean opsin evolution in context, phylogenetic studies of two crustacean groups (Mysidae and Decapoda) were completed. Studies of Mysidae utilized 16S mtDNA, and 18S and 28S rDNA to reconstruct phylogenetic relationships and assess newly developed Bayesian methods of assessing pattern heterogeneity. Using this suite of genetic markers, there are incongruencies between current taxonomy and inferred phylogenetic relationships. Studies of Decapoda assessed phylogenetic relationships and estimated divergence times using 16S mtDNA, H3 nDNA, and 18S and 28S rDNA sequence data in conjunction with a set of eight fossil calibrations. Reconstructed phylogenies show support for two well supported nodes corresponding to the Pleocyemata and the informal 'Reptantia' and place the emergence of the Decapod lineage in the early Devonian (407 MYA). Finally, opsin sequences and spectral sensitivity data from species within the Mysidae and Decapoda were combined with previously characterized invertebrate sequences to investigate opsin evolution. Standard dN/dS methods did not detect any evidence of selection. Methods investigating selection on amino acid properties, however, identified four properties (coil tendencies, compressibility, power to be at the middle of the alpha helix, and refractive index) to be under positive destabilizing selection. These properties occurred mostly at sites in transmembrane helices and included residues previously identified to affect spectral tuning as well as identifying novel sites. Thesis (Ph. D.)--Brigham Young University. Dept. of Microbiology and Molecular Biology, 2005. Includes bibliographical references (p. 163-189).
  • [Show abstract] [Hide abstract]
    ABSTRACT: The role of the two distinct retinal photoreceptor organs in photoreception for photoperiodism was examined in the carabid beetle, Leptocarabus kumagaii, by surgical removal. This beetle shows long-day and short-day photoperiodic responses in the larval and adult stages, respectively. Larval diapause in the final instar is induced under short-day conditions whereas pupation occurs without diapause under long-day conditions. Adult reproductive diapause is terminated under short-day conditions but maintained under long-day conditions. The stemmata of the larvae and compound eyes of the adults were removed and the responses of the animals to photoperiod were compared to those of intact beetles. When all the stemmata were removed, larvae pupated without entering diapause under both long-day and short-day conditions, indicating that the larvae lacking stemmata were incapable of photoreception for photoperiodism. As in other holometabolous insects, the stemmata migrated into the brain during metamorphosis and remained rudimentarily in the optic lobe of the adult brain. However, these stemmata-derived organs were found to be no longer necessary for photoperiodism, because adults lacking the stemmata-derived organs responded to photoperiod normally. By contrast, removal of the compound eyes in adults resulted in the termination of reproductive diapause under both long-day and short-day conditions, indicating that photoreception for photoperiodism in the adult stage is performed by the compound eyes. Therefore, the site of photoperiodic photoreception in L. kumagaii appear to change from the stemmata to the compound eyes during metamorphosis.
    Journal of Experimental Biology 11/2009; 212(Pt 22):3651-5. · 3.00 Impact Factor

Full-text (2 Sources)

Available from
May 15, 2014