This week’s BEACON Researchers at Work blog post is by University of California at Irvine graduate student Aide Macias-Muñoz.
My interest in biology began when I was very young with my fascination in living things. My exposure to diverse plants and animals mostly took place every summer when I traveled with my family to Nochistlan, Zac., Mexico. I was very interested in the care of domesticated farm animals and the large diversity of moths and butterflies that I saw in this small town and rural surroundings. I often overwhelmed my parents with questions that they did not have the answers to.
During my undergraduate career at UC Berkeley, I majored in Integrative Biology and took a broad range of courses. Through these courses I began to learn the answers to many of the questions that I had as a child, and, in the process new questions emerged. After joining Adriana Briscoe’s lab at UC Irvine, I acquired new skills in molecular biology and bioinformatics and began tackling these questions.
Our lab uses different approaches to investigate the evolution of sensory systems in insects, primarily focusing on evolution of vision in butterflies. My role in the lab has been to explore gene expression by creating and analyzing RNA-Sequencing libraries. My most recent project sought to understand how gene expression of vision-related genes changes in a species that exhibits phenotypic plasticity for vision.
Bicyclus anynana is a butterfly species that has two seasonal forms corresponding to the wet and dry season. The distinct seasonal forms display an interesting behavior of sex role reversal. In the wet season, males court females, which choose mates based on UV-reflectance of the dorsal forewing eyespot pupils. However, in the dry season, females court males that now exhibit choosy behavior (Prudic et al. 2011). A previous study, showed that eye size varied between sexes and seasonal forms; males had larger eyes relative to females and wet season forms had larger eyes in both sexes relative to dry season forms. In addition, opsin expression complemented sex role reversal; long-wavelength, blue, and ultraviolet opsin genes had decreased expression in non-choosy dry season female butterflies (Everett et al. 2012).
Photo credit: Antónia Monteiro. Bicyclus anynana wet and dry season form mating. The wet season form has conspicuous eyespots and a pale band on its wings, while the dry season form has cryptic coloration and reduced eyespots.
In order to see what additional vision-related genes were associated with eye size differences, we did a differential expression analysis of sexes and seasonal forms. We found that non-choosy dry season females do indeed down-regulate blue and ultraviolet opsin mRNA relative to wet season females. We also identified two eye development genes and an eye pigment biosynthesis gene differentially expressed between seasonal forms. Upon closer inspection, we found that the biggest magnitude change was in dry season females.
Our results show that differential expression of eye development and eye pigment genes is associated with divergent eye phenotypes in B. anynana seasonal forms, and that there is a larger effect of season on female vision-related genes. This difference is potentially due to variation in energetic demands between the sexes. Females have the additional metabolic burden of producing eggs and thus may be under greater selective pressure to reduce non-essential physiological functions (Macias-Muñoz et al. In Press).
References:
Prudic KL, Jeon C, Cao H, Monteiro A. 2011. Developmental plasticity in sexual roles of butterfly species drives mutual sexual ornamentation. Science 331:73–75.
Everett A, Tong X, Briscoe AD, Monteiro A. 2012. Phenotypic plasticity in opsin expression in a butterfly compound eye complements sex role reversal. BMC Evol Biol. 12:232.
Macias-Muñoz A, Smith G, Monteiro A, Briscoe AD. Transcriptome-wide differential gene expression in Bicyclus anynana butterflies: Female vision-related genes are more plastic. MBE. In Press. doi: 10.1093/molbev/msv197
For more information about Aide’s work, you can contact her at amaciasm at uci dot edu.
