Poster Annual Conference of the Genetics Society of Australasia with the NZ Society for Biochemistry & Molecular Biology

Identification and characterisation of two putative ecdysteroid kinases in Drosophila melanogaster (718)

Jack Scanlan 1 , Rebecca Smith 1 , Charles Robin 1
  1. University of Melbourne, North Melbourne, VICTORIA, Australia

Ecdysteroids regulate arthropod development, reproduction and behaviour. In insects, ecdysteroid activity is modulated by reversible conjugation reactions, the most common of which is phosphorylation. However, the functions of specific phosphate conjugates, and the identities of the kinases that synthesise them, are almost entirely unknown. 26-hydroxylation is an intermediate step in the irreversible 26-carboxylation of ecdysteroids, an essential deactivation reaction during development. In the Drosophila melanogaster S2 cell line, 26-carboxylation is blocked by the formation of 26-phosphate conjugates, suggesting ecdysteroid catabolism may be regulated by the activity of ecdysteroid kinases throughout insect development. We hypothesise that CG13813, a member of the poorly characterised EcKinase gene family, encodes the ecdysteroid 26-kinase active in S2 cells, due to a collated body of published data, including its regulation by ecdysteroids and ecdysteroid-response pathways, and its unique co-expression with the ecdysteroid 26-hydroxylase Cyp18a1. Our phylogenetic analyses of EcKinases demonstrate that CG13813 and its paralog CG1561 are orthologs of the only characterised ecdysteroid kinase, found in Bombyx mori. Functional analyses of CG13813 and CG1561 show they are essential for development at the embryonic/larval and pupal stages, respectively. Intriguingly, knockdown of CG1561 produces a "drowning in food" phenotype post-eclosion and head eversion failure, and its ectopic misexpression during development blocks pupariation, consistent with a capacity to also regulate ecdysteroid signalling. Our ongoing work will explore the functions of ecdysteroid-phosphate conjugates by characterising the genes responsible for their formation.