# Transcriptomic, proteomic and biochemical comparison of luminescent and non‐luminescent Keroplatinae larvae (Diptera: Keroplatidae)

## TL;DR

This study compares the genes and proteins in glowing and non-glowing Keroplatinae larvae to understand the role of compounds involved in bioluminescence.

## Contribution

The study identifies shared molecular components in bioluminescent and non-bioluminescent larvae, suggesting broader physiological roles for these compounds.

## Key findings

- SBF contains hexamerins, flavin-dependent reductases, keroplatin, and riboflavin in both luminescent and non-luminescent larvae.
- Neoditomyia sp. lacks luciferase activity despite similar luciferase protein patterns to O. fultoni.
- SBF reductases may be involved in keroplatin synthesis or reduction in both species.

## Abstract

Bioluminescence (BL) in the Keroplatinae subfamily (Diptera: Keroplatidae) is found in Keroplatus, Neoceroplatus and
Orfelia fultoni
larvae. In
O. fultoni
, BL involves an oligomeric luciferase, a luciferin called keroplatin, which is associated with a substrate binding fraction (SBF), whose molecular identity and function remain uncertain. Non‐luminescent web‐constructing predatory larvae of Neoditomyia sp. (Keroplatinae) also contain keroplatin and SBF in their bodies, suggesting additional unknown roles for this compound in this subfamily. To identify gene products differentially expressed between luminescent and non‐luminescent larvae, especially those associated with luciferase, SBF and keroplatin synthesis, here we compared the transcriptional and proteomic profiles of Neoditomyia sp.,
O. fultoni
and Arachnocampa larvae and conducted biochemical assays. Similarly to
O. fultoni
, Neoditomyia sp. displays an abundance of hexamerin isoforms and transcripts associated with the tryptophan and kynurenine pathway, which is potentially involved with keroplatin synthesis and silk production. Despite displaying a similar electrophoretic pattern of Orfelia luciferase purified fractions, no luciferase activity was detected in Neoditomyia purified fractions. The SBF‐enriched fractions from
O. fultoni
and Neoditomyia revealed a similar abundance of hexamerins, the presence of flavin‐dependent reductases, keroplatin and riboflavin. The results indicate that the SBF consists of protein aggregates associated with riboflavin and keroplatin, which is used as luciferin in bioluminescent species and for other still unveiled physiological functions in non‐luminescent species.

Transcriptomic and proteomic comparison of luminescent
O. fultoni
and non‐luminescent Neoditomyia sp show that the substrate binding fraction (SBF) has a similar abundance of hexamerins and the presence of flavin‐dependent reductases.In addition to the high content of keroplatin, SBF also contains considerable amounts of riboflavin and displays reductase activity.The SBF reductases may participate in the reduction or synthesis of keroplatin and other compounds.

Transcriptomic and proteomic comparison of luminescent
O. fultoni
and non‐luminescent Neoditomyia sp show that the substrate binding fraction (SBF) has a similar abundance of hexamerins and the presence of flavin‐dependent reductases.

In addition to the high content of keroplatin, SBF also contains considerable amounts of riboflavin and displays reductase activity.

The SBF reductases may participate in the reduction or synthesis of keroplatin and other compounds.