Abstracts

Bioluminescence in Keroplatinae larvae is observed in Keroplatus, Neoceroplatus, and Orfelia. The bioluminescence involves a multimeric luciferase, a luciferin called keroplatin, and a Substrate Binding Fraction (SBF), whose molecular identity and function still remains uncertain. Interestingly, non-luminescent web-constructing predatory larvae of Neoditomyia sp. (Keroplatinae) also contain keroplatin in their bodies, suggesting additional unknown roles for this compound in non-bioluminescent species. In order to gain better understanding of the biochemical requirements of the bioluminescent system in the Keroplatinae subfamily, we compared the transcriptional and proteomic profiles of Neoditomyia sp. with Orfelia fultoni and Arachnocampa luminosa larvae, and also performed biochemical assays. The transcriptional profiles of the non-luminescent Neoditomyia sp. and the bioluminescent O. fultoni larvae are quite similar, with an abundance of gene products related to web synthesis that is consistent with the similar ecology of these predators and web-constructing larvae inhabiting humid habitats. Neoditomyia larvae transcriptomes also exhibit an abundance of gene products associated with the pteridin derivatives pathways, Co-A-ligases, and hexamerins, which were previously associated with bioluminescence in this subfamily. Noteworthy, the SBF enriched fraction of both Orfelia and Neoditomyia sp. displayed a high content of riboflavin, and NADH-dependent reductase activity involved in reducing keroplatin (luciferin), results which are corroborated by the presence of flavin-reductases in the transcriptional and proteomic analysis. These results indicate that the enigmatic SBF, which is the main component of the black bodies, consists of protein complexes composed of hexamerins, flavin-reductases associated with keroplatin and riboflavin, in which one of the possible biological functions is to keep luciferin and other compounds in the reduced form in bioluminescent species, as well as for other biological purposes in non-luminescent species.