3.2. Effect of LAB ingestion on the expression of immune genes in
honeybees
The mRNA expression levels of immune-related genes were
determined in adult workers and larvae 24 h after feeding the
LAB-containing artificial diet. The 9 LAB strains listed in Table 1
were used for feeding experiments. Among the larvae, transcripts
of all the antimicrobial peptide genes (abaecin, defensin and hymehymenoptaecin)
increased significantly in response to ingestion of strain
577 when compared with the control (P < 0.05) (Fig. 2). Elevated
mRNA levels for defensin were also observed for strain 102. Compared
to the control, feeding the larvae any of the other strains was
not associated with the expression of antimicrobial peptide genes.
In the adult workers, however, when compared to the controls,
ingestion of strain F13 induced significant changes in abaecin
and hymenoptaecin mRNA expression (P < 0.05), although no similar
association was observed for defensin expression (Fig. 3). None
of the LAB assayed in this study (listed in Table 1) had any deleterious
effects on honeybee larvae and adults (Figs. S1 and S2).