Mating Stimulates the Immune Response and Sperm Storage-Related Genes Expression in Spermathecae of Bumblebee (Bombus terrestris) Queen

Abstract

Bumblebee queens have remarkable spermathecae that store sperm for year-round reproduction. The spermathecal gland is regarded as a secretory organ that could benefit sperm storage. Queen mating provokes substantial physiological, behavioral, and gene expression changes. Here, the transcriptomes of spermathecae were compared between virgins and mated queens of the bumblebee, Bombus terrestris L., at 24 h post mating. Differentially expressed genes were further validated by real time quantitative PCR and immunofluorescence assay. In total, the expression of 11, 069 and 10, 862 genes were identified in virgins and mated queens, respectively. We identified that 176 differentially expressed genes between virgin and mated queen spermathecae: 110 (62.5%) genes were upregulated, and 66 (37.5%) genes were downregulated in mated queens. Most of the differentially expressed genes validated by RT-qPCR were concentrated on immune response [i.e., leucine-rich repeat-containing protein 70 (35.8-fold), phenoloxidase 2 (41.9-fold), and defensin (4.9-fold)] and sperm storage [i.e., chymotrypsin inhibitor (6.2-fold), trehalose transporter Tret1 (1.7-, 1.9-, 2.4-, and 2.4-fold), and heterogeneous nuclear ribonucleoprotein A3 (1.2-, and 2.6-fold)] functions in the spermathecae of mated queens. Procollagen-lysine, 2-oxoglutarate 5-dioxygenase 1 (PLOD1) was hypothesized to promote the mating behavior according to RT-qPCR and immunofluorescence assay. The expression levels of most upregulated immune genes were decreased significantly at 3 days post mating. In conclusion, the external sperm transfer into spermathecae led to the significantly upregulated immune response genes in bumblebees. These gene expression differences in queen spermathecae contribute to understanding the bumblebee post mating regulatory network.

Long‐term sperm storage in eusocial Hymenoptera

“…In Acromyrmex echinatior and A. colombica leafcutter ants, the expression of two antimicrobial peptides – abaecin and defensin – is upregulated in the male reproductive organs (accessory glands and testes) and in the spermatheca of virgin and mated queens (Chérasse et al ., 2018). Furthermore, in the bumble bee B. terrestris , defensin was upregulated in the spermatheca following mating (Guo et al ., 2021). Second, experimental studies have convincingly demonstrated that male and female reproductive tissues display antimicrobial activity.…”

“…antimicrobial peptides), rather than via a generalized immune response which could potentially lead to sperm death. However, in B. terrestris , transcriptomic analyses recently showed that PO is upregulated in queen spermatheca after mating (Guo et al ., 2021), suggesting that antimicrobial strategies may differ among social insects depending on their specific life histories. For example, bumble bee queens usually have much shorter reproductive lifespans than ant queens.…”

“…For example, bumble bee queens usually have much shorter reproductive lifespans than ant queens. (Guo et al ., 2021).…”

Untargeted Lipidomics Analysis Unravels the Different Metabolites in the Fat Body of Mated Bumblebee (Bombus terrestris) Queens

“…Most insects reproduce sexually, and the physiology and behavior of female insects change post mating [12][13][14][15][16][17]. After honey bee and bumblebee queens mate with drones, the expressions of immune-and sperm storage-related genes in spermathecae are significantly up-regulated [18,19]. Copulation also stimulates the activation of acquired immunity in the haemolymph of bumblebees, and the immunity is maintained continuously during diapause [20].…”