Expression levels of glutamate and serotonin receptor genes in the brain of different behavioural phenotypes of worker honeybee (Apis mellifera)

Abstract

Social insect colonies are known for their efficient system of task specialization. In this study, we analyzed the brain expression level of glutamate and serotonin receptor genes in different behavioural phenotypes of (Apis mellifera) workers by qRT-PCR. The glutamate receptor genes include the ionotropic glutamate receptor (iGluR) genes and metabotropic glutamate receptor (mGluRs) genes, and has 9 orthologous genes in honeybee, such as the N-methyl-D-aspartate receptor (NMDAR) genes, NMDAR1 and NMDAR2, the α-amino-3-hydroxy-5-methyl-4-isoxazole receptor (AMPAR) genes, AMPAR Δ2-a, AMPAR Δ2-b, AMPAR Δ2-c, AMPAR Δ2-d, and the mGluR1, mGluR4 and mGluR7. Our results showed that: the relative expression level of NMDAR genes was much higher in newly emerged workers (NW) than in young nurses (YN) and "old" foragers (OF) (P < 0.001); both NW and YN had a significantly higher relative expression level of AMPAR Δ2-b, AMPAR Δ2-c and AMPAR Δ2-d than in OF (P < 0.05). than in YN and OF; the relative expression level of mGluR7 gene in OF was significantly higher than in NW (P > 0.05), but there were no significant differences among NW, YN, and OF for the relative expression level of mGluR1 and mGluR4 gene (P > 0.05); in the case of Serotonin (5-HT), the relative expression level of the 5-HT1 gene showed no significant difference between YN and OF (P > 0.05), but was higher in YN and OF than in NW (P < 0.001). Above results indicate that some glutamate and serotonin receptor genes may play important roles in honeybee age-dependent role change.