Honey bee trypanosomatid parasite dynamically changes the transcriptome during the infection of honey bee and modifies the host physiology

Abstract

18Although there are many honey bee pathogens/parasites, it is still not understood how 19 they change their gene expression to adapt to the host environment or how the host 20 simultaneously responds to pathogen/parasite infection by modifying its own gene 21 expression. Such interactions must lead to changes in the physiological states of both 22 host and parasite. To address this question, we studied a trypanosomatid, 23 Lotmaria passim, which can be cultured in medium and inhabit the honey bee hindgut. 24 We found that L. passim dynamically modifies the expression of mRNAs associated 25 with protein translation and the electron transport chain to adapt to the anaerobic and 26 nutritionally poor honey bee hindgut at early stages of infection, and to become dormant 27 at late stages of infection. Meanwhile, several genes are continuously up-or 28 down-regulated during infection, including GP63 as well as genes coding for host cell 29 signaling pathway modulators (up-regulated), and those involved in detoxification of 30 radical oxygen species as well as flagellar formation (down-regulated). L. passim 31 infection only slightly increases honey bee mortality and does not affect the number of 32 microorganisms in the gut microbiota; but it induces honey bee innate immune response. 33 Upon infection, the host appears to be in poor nutritional status, indicated by the 34 increase in the levels of mRNAs for take-out and facilitated trehalose transporter and 35 the decrease of vitellogenin mRNA level. Simultaneous gene expression profiling of L. 36 passim and honey bee during infection provided insight into how both parasite and host 37 modify their gene expressions. This study presents one of the best models to understand 38 host-parasite interactions at the molecular and cellular levels in honey bee. 39 40 41 42

Gene Disruption of Honey Bee Trypanosomatid Parasite, Lotmaria passim, by CRISPR/Cas9 System

“…We also successfully disrupted tyrosine aminotransferase ( LpTAT ) using Cas9-induced HDR as described above (Figure 7). LpTAT is one of L. passim genes that become upregulated upon infection of the honey bee hindgut (Liu et al, 2019). As shown in Figure 8A, growth rate of LpMT or LpTAT null mutant was comparable to that of wild type, suggesting that these two genes are not essential for the parasite's growth in the culture medium.…”

“…The genes essential for survival could be identified by the absence of homozygous null mutants, and the genes necessary for optimal growth in the culture medium could also be tested. More importantly, we identified L. passim mRNAs up- or down-regulated during the infection of honey bee hindgut; for example, LpGP63 mRNA is continuously up-regulated (Liu et al, 2019). We could therefore establish LpGP63 mutant by CRISPR/Cas9, and then test the phenotypes by infecting honey bees.…”