Top: Eyespot (left) & Crescent (right) markings on a silkworm caterpillar are controlled by regulator factor, +p.
Bottom: Mutation in a regulatory factor (p) leads to loss of eyespot and crescent markings.
Image: Shinichi and colleagues*
Many caterpillars have eyespots and other markings that adapt a caterpillar to its environment. How is the shape and location of the eyespots determined? The process involves gene regulation. The Silkworm, Bombyx mori,
has many color pattern mutations available for study. A group of scientists
* have used these mutations to identify the regulatory gene that controls eyespot formation. In areas of eyespot formation, a regulatory gene called apontic-like
is a key switch that turns on the pigment production and melanin synthesis in the cuticle cells where the spot is located. The gene can have multiple alleles (forms). Different alleles can produce different color patterns or in some case no pattern.
Future studies can look for regulatory factors that control the apontic-like gene or how the gene stimulates the cells under the eyespot to produce pigment. This research helps understand the control of gene expression of many traits including morphological features, not just color spots.
*Shinichi Yoda, Junichi Yamaguchi, Kazuei Mita, Kimiko Yamamoto, Yutaka Banno, Toshiya Ando, Takaaki Daimon & Haruhiko Fujiwara. 2014. The transcription factor apontic-like controls diverse colouration pattern in caterpillars. Nature Communications 5, Article number: 4936