Transcriptional comparison of the photogenic and non-photogenic tissues of Phrixothrix hirtus (Coleoptera: Phengodidae) and non-luminescent Chauliognathus flavipes (Coleoptera: Cantharidae) give insights on the origin of lanterns in railroad worms

- Comparison of photogenic and non-photogenic tissues in bioluminescent and non-bioluminescent related species in Elateroidea
- Presence of gene products related to bioluminescence in the fat body of non-bioluminescent Cantharidae
- Non-luminescent Elateroidae families may also display latent bioluminescent potential.
- The fat body of P. hirtus displays low amount of gene products related to bioluminescence;
- Photogenic tissue of phengodid lanterns did not evolved from the fat body and has distinct origin from fireflies' lanterns.

Bioluminescence in beetles is found in the Elateroidea superfamily, which includes Elateridae, Lampyridae, Rhagophthalmidae, and Phengodidae families. Despite sharing the same biochemical system, it is unclear whether the lanterns and the bioluminescent system share a common origin or not. To better understand the molecular differentiation of photogenic from non-photogenic tissues and the molecular physiology of these tissues, we compared the transcriptional profiles of the lateral lanterns and fat body in Phrixothrix hirtus railroad worm (Phengodidae) and the abdomen of the non-luminescent Chauliognathus flavipes (Cantharidae). We observed gene products involved in pheromone biosynthesis in all tissues and four distinct opsin gene products in C. flavipes, more than expected when compared to the transcriptional analysis of lampyrid eyes. We also observed several gene products potentially associated with bioluminescence in P. hirtus lantern and in C. flavipes body, whereas in the fat body of P. hirtus we found only a single copy of luciferase homolog enzyme. Altogether these results suggest that the photogenic tissue of phengodid lanterns has distinct origin from fireflies lanterns, and also the existence of a latent bioluminescent potential in the fat body tissue of some Elateroidea families.

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