Homology search confirms widespread presence of BBSome proteins in Hexapoda with implications for potential non-ciliary BBS protein functions in honey bees

Abstract

Cilia were one of the characteristic traits of the last eukaryotic common ancestor and are highly conserved among eukaryotes. Their proteomic makeup is remarkably similar throughout all eukaryotic lineages. Recently, several ciliary transport proteins, namely the Bardet-Biedl Syndrome (BBS) proteins, were shown to traverse the nuclear envelope, and to modulate gene expression. Insects have been critically understudied in cilia biology since they only exhibit cilia on a subset of cells. We present evidence that the BBSome is largely conserved in multiple insect lineages. To examine BBS protein expression within insects, we profiled tissues, castes, and sexes of the honeybee Apis mellifera, a species where the genome encodes for multiple behavioural and morphological phenotypes. We find variation in expression profiles of putative BBSome-associated genes across different tissues, including those lacking cilia, indicating possible non-ciliary functions. We also demonstrate that expression of individual BBS proteins varies significantly between queens’ and males’ tissues, especially in neuronal tissue. Particularly high overexpression of BBS4 in glandular tissue indicates a cilia-independent role. Our findings provide evolutionary insight into the conservation of BBSome components across insects, suggesting potential additional roles for cilia proteins in non-ciliated tissues, providing candidate genes from diverse insect orders for future experimental work.