Evaluation of differential gene expression during behavioral development in the honeybee using microarrays and northern blots

Abstract

Background: The honeybee (Apis mellifera) has been used with great success in a variety of behavioral studies. The lack of genomic tools in this species has, however, hampered efforts to provide genome-based explanations for behavioral data. We have combined the power of DNA arrays and the availability of distinct behavioral stages in honeybees to explore the dynamics of gene expression during adult development in this insect. In addition, we used caffeine treatment, a procedure that accelerates learning abilities in honeybees, to examine changes in gene expression underlying drug-induced behavioral modifications.

Results: Spotted microarrays containing several thousand cDNAs were interrogated with RNAs extracted from newly emerged worker bees, experienced foragers and caffeine-treated bees. Thirty-six differentially expressed cDNAs were verified by northern blot hybridization and characterized in silico by sequencing and database searches. Experienced foragers overexpressed royal jelly proteins, a putative imaginal disc growth factor, a transcriptional regulator (Stck) and several enzymes, including alpha-glucosidases, aminopeptidases and glucose dehydrogenase. Naive workers showed increased expression of members of the SPARC and lectin families, heat-shock cognate proteins and several proteins related to RNA translation and mitochondrial function. A number of novel genes overexpressed in both naive and experienced bees, and genes induced by caffeine, have also been identified.

Conclusions: We have shown the usefulness of this transcriptome-based approach for gene discovery, in particular in the context of the efficacy of drug treatment, in a model organism in which routine genetic techniques cannot be applied easily.

Figure 1

Differential expression of 36 ESTs (indicated by red boxes) detected by microarrays and confirmed by northern blotting (lower panels for each EST). The three columns correspond to transcripts identified as differentially expressed in the heads and abdomens of newly born bees and experienced foragers, and in the heads of 3-day-old bees after caffeine treatment.

Figure 2

Northern blot hybridization showing the pattern of expression of selected genes in the head, thorax and abdomen. (a) Genes downregulated in foragers; (b) genes upregulated in foragers; (c) genes predominantly expressed in only one compartment.