Transcriptome analysis of the Molecular Mechanism underlying Immunity- and Reproduction trade-off in Locusta migratoria Infected by Micrococcus luteus

Immune response and reproductive success are two of the main energy-consuming processes in living organisms. However, it is unclear which process is prioritized when both are required. Therefore, the present study was designed to examine this question using one of the world’s most destructive agricultural pests, the migratory locust Locusta migratoria. Transcripts from the ovaries and fat bodies of newly emerged locusts were analyzed, using RNA-seq based transcriptome and qualitative real-time PCR, at 4 h and 6 d after being infected with the gram-positive bacteria Microcroccus luteus, and changes in the main biological pathways involved in reproduction and immunization were analyzed using bioinformatics. At 4 h after infection, 348 and 133 transcripts were up- and down-regulated, respectively, whereas 5699 and 44 transcripts were up- and down-regulated, respectively, at 6 d after infection. Meanwhile, KEGG analysis indicated that vital pathways related with immunity and reproduction, such as Insulin resistance, FoxO signaling, Lysosome, mTOR signaling, and Toll-like receptor signaling pathways were up-regulated. Among the differentially expressed genes, 22 and 17 were related to immunity and reproduction, respectively, and the expression levels of PPO1 and antimicrobial peptide defensin 3 were increased (log 2 FC = 5.93 and 6.75, respectively), whereas those of VgA and VgB were reduced (log 2 FC = −17.82 and −18.13, respectively). These results indicated that that locusts allocate energy and resources to maintain their own survival by increasing immune response when dealing with both immune and reproductive processes. The present study provides the first report of expression levels for genes related with reproduction and immunity in locusts, thereby providing a reference for future studies, as well as theoretical guidance for investigations of locust control.