Hsp70 affects memory formation and behaviourally relevant gene expression in Drosophila melanogaster.
Heat shock proteins (Hsps), in particular Hsp70, play a central role in proteostasis in eukaryotic cells. Due to its chaperone properties, Hsp70 is involved in various processes both after stress and under normal physiological conditions. In contrast to mammals and many Diptera species, members of the Hsp70 family in Drosophila are constitutively synthesized at a low level and undergo dramatic induction after temperature elevation or other forms of stress. In the courtship suppression paradigm used in this study, Drosophila males that have been repeatedly rejected by mated females during courtship are less likely than naive males to court other females. Although numerous genes with known function were identified to play important roles in long-term memory, there is, to the best of our knowledge, no direct evidence implicating Hsp70 in this process. To eliminate this gap, we used D. melanogaster strains containing different hsp70 copy numbers, including strains carrying a deletion of all six hsp70 genes. Our investigations exploring the memory of courtship rejection paradigm demonstrated that a low constitutive level of Hsp70 is required for learning and the formation of short and long-term memories in males. The performed transcriptomic studies demonstrate that males with different hsp70 copy numbers differ significantly in the expression of a few definite groups of genes involved in mating and reproduction, as well as methionine metabolism and immune genes in response to rejection. Specifically, our analysis reveals several major pathways that depend on the presence of hsp70 copies in the genome and apparently participate in memory formation and consolidation, including the cAMP signalling cascade. Overall design: Deep RNA sequencing of Drosophila melanogaster heads