RNAi-induced phenotypes suggest a novel role for a chemosensory protein CSP5 in the development of embryonic integument in the honeybee (Apis mellifera)
Small chemosensory proteins (CSPs) belong to a conserved, but poorly understood, protein family found in insects and other arthropods. They exhibit both broad and restricted expression patterns during development. In this paper, we used a combination of genome annotation, transcriptional profiling and RNA interference to unravel the functional significance of a honeybee gene (csp5) belonging to the CSP family. We show that csp5 expression resembles the maternal-zygotic pattern that is characterized by the initiation of transcription in the ovary and the replacement of maternal mRNA with embryonic mRNA. Blocking the embryonic expression of csp5 with double-stranded RNA causes abnormalities in all body parts where csp5 is highly expressed. The treated embryos show a “diffuse”, often grotesque morphology, and the head skeleton appears to be severely affected. They are ‘unable-to-hatch’ and cannot progress to the larval stages. Our findings reveal a novel, essential role for this gene family and suggest that csp5 (unable-to-hatch) is an ectodermal gene involved in embryonic integument formation. Our study confirms the utility of an RNAi approach to functional characterization of novel developmental genes uncovered by the honeybee genome project and provides a starting point for further studies on embryonic integument formation in this insect.
KeywordsInsect cuticle Embryonic development Gene silencing CSP family
Martin Beye, Martin Hassleman and Eldon Ball provided advice and protocols for which we are grateful. We also thank Paul Helliwell for mastering a ‘perfect’ injecting technique and for excellent bee keeping.
- Jung-Offmann I (1968) Traité de biologie de l’abeille, chapter Développement et croissance. Masson, pp 69–144Google Scholar
- King RC (1985) Comprehensive insect physiology, biochemistry and pharmacology, vol 1, chapter The origin and functioning of insect oocytes and nurse cells. Pergamon, pp 37–82Google Scholar
- Nelson JA (1915) The embryology of the honeybee. Princeton University PressGoogle Scholar
- Schal C, Sevala V, Young HP, Bachmann JAS (1998) Sites of synthesis and transport pathways of insect hydrocarbons: cuticle and ovary as target tissues. Am Zool 38:382–393Google Scholar
- Vogt RG (2004) Molecular basis of pheromone detection in insects. In: Gilbert LI, Iatro K, Gill S (eds) Comprehensive molecular insect science, vol 3. Elsevier, pp 753–803Google Scholar