論文の公開元へMicrobes control Drosophila germline stem cell increase and egg maturation through hormonal pathways
概要
Title
Microbes control Drosophila germline stem cell
increase and egg maturation through hormonal
pathways
Author(s)
Suyama, Ritsuko; Cetraro, Nicolas; Yew, Joanne
Y. et al.
Citation
Communications Biology. 2023, 6(1), p. 1287
Version Type VoR
URL
rights
https://hdl.handle.net/11094/93535
This article is licensed under a Creative
Commons Attribution 4.0 International License.
Note
Osaka University Knowledge Archive : OUKA
https://ir.library.osaka-u.ac.jp/
Osaka University
ARTICLE
https://doi.org/10.1038/s42003-023-05660-x
OPEN
Microbes control Drosophila germline stem cell
increase and egg maturation through hormonal
pathways
1234567890():,;
Ritsuko Suyama
1 ✉,
Nicolas Cetraro2, Joanne Y. Yew
2✉
& Toshie Kai
1✉
Reproduction is highly dependent on environmental and physiological factors including
nutrition, mating stimuli and microbes. Among these factors, microbes facilitate vital functions for host animals such as nutritional intake, metabolic regulation, and enhancing fertility
under poor nutrition conditions. However, detailed molecular mechanisms by which microbes
control germline maturation, leading to reproduction, remain largely unknown. In this study,
we show that environmental microbes exert a beneficial effect on Drosophila oogenesis by
promoting germline stem cell (GSC) proliferation and subsequent egg maturation via
acceleration of ovarian cell division and suppression of apoptosis. Moreover, insulin-related
signaling is not required; rather, the ecdysone pathway is necessary for microbe-induced
increase of GSCs and promotion of egg maturation, while juvenile hormone contributes only
to increasing GSC numbers, suggesting that hormonal pathways are activated at different
stages of oogenesis. Our findings reveal that environmental microbes can enhance host
reproductivity by modulating host hormone release and promoting oogenesis.
1 Laboratory of Germline Biology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka Suita, Osaka 565-0871, Japan. 2 Pacific
Biosciences Research Center, University of Hawai’i at Manoa, 1993 East-West Road, Honolulu, HI 96822, USA. ✉email: rrsuyama@fbs.osaka-u.ac.jp;
suyama.ritsuko.fbs@osaka-u.ac.jp; jyew@hawaii.edu; kai.toshie.fbs@osaka-u.ac.jp
COMMUNICATIONS BIOLOGY | (2023)6:1287 | https://doi.org/10.1038/s42003-023-05660-x | www.nature.com/commsbio
1
ARTICLE
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COMMUNICATIONS BIOLOGY | https://doi.org/10.1038/s42003-023-05660-x
nvironmental factors, such as stress, age, nutritional status,
and mating, can have a large effect on animal physiology by
regulating homeostatic systems1,2. Among environmental
influences, the microbiome, the community of fungi and bacteria
in host organisms, exerts enormous influence on vital functions
such as nutrient intake, immune responses, metabolic homeostasis and reproduction3–9. In particular, reproduction, which
requires more energy than any other physiological function, is
tightly regulated by both environmental signals and internal
homeostatic mechanisms.
Drosophila oogenesis is initiated by germline stem cells (GSCs)
localized at the anterior of the germarium. Maintaining stem cell
lineage depends on local signals from the proximal somatic
microenvironment, a niche composed of cap cells, escort stem
cells and terminal filament cells10. GSCs proliferate and differentiate into 16-cell cysts, resulting in an oocyte and 15 nurse cells
after four rounds of incomplete cytokinesis in the germarium10.
Germ cysts are then enveloped by the somatic follicle cells and the
oocyte becomes a mature egg by receiving essential substances,
such as organelles, mRNAs, and proteins from nurse cells11,12.
During egg maturation, programmed cell death (PCD) acts as a
checkpoint at the germarium and mid-stage, modulating the
entire oogenesis process, including egg production13,14. These
processes are controlled by several environmental factors via
three major hormonal systems: insulin-like peptides, 20hydroxyecdysone (20E), and juvenile hormone (JH). Receptors
for these hormones are expressed in the ovarian nurse and follicle
cells of the ovary15–18, and a lack of these hormones causes
deterioration of oogenesis1.
Germline development and fecundity are influenced by nutritional
status and mating. Their regulatory molecular mechanisms of ovarian
development and inherent hormonal pathways are well
characterized1,9. Female flies reared with a nutrition-rich diet lay
more eggs and proliferate more GSCs than those in poor nutrition
conditions2,14,19–23. Particularly, rich nutrition promotes oogenesis
via Drosophila insulin-like peptides (dilps) that are produced in brain
neuroendocrine cells and the gut19,20. In contrast, mating enhances
oogenesis by activating neural pathways via ecdysone signaling24,25.
The steroid hormone, 20-hydroxyecdysone (20E) is produced in the
adult reproductive organs, gut, and head and helps to coordinate
metabolic state with GSC and follicle cell maintenance and proliferation, and promote vitellogenesis during oogenesis15,22,26–35.
Microbes modulate host homeostasis and influence host physiology, resulting in trade-offs between reproduction and
longevity7. Inoculating Drosophila with several different species of
microbes improves fertility or prolongs longevity, indicating that
individual microbe strains can control host physiology in distinct
ways3,7. Microbes also accelerate embryonic maturation and
metabolic homeostasis via alcohol dehydrogenase to enhance egg
production3,36. However, little is known about the detailed
molecular mechanisms of host reproduction and oogenesis that
are influenced by microbes.
Here, we dissect the molecular and cellular mechanisms by
which microbes influence oogenesis in D. melanogaster. Genetic
analysis revealed that microbes enhance oogenesis through multiple mechanisms: GSC proliferation accompanied by activation
of mitotic division, repression of cell death at two critical developmental checkpoints, and acceleration of the cell division of
germline and follicle cells. Furthermore, the ecdysone hormone
pathway appears to be a key mediator of microbe-induced processes during oogenesis at the GSC and later vitellogenic stages.
In contrast, the juvenile hormone pathway is involved in GSC
proliferation. We propose that microbes regulate different stages
of oogenesis, possibly by modulating hormone levels and their
subsequent pathways, and are able to contribute to host fecundity
under poor nutrition conditions.
2
Results
Environmental microbes regulate oogenesis by egg maturation.
Drosophila acquires microbes from environmental sources
including dietary substrates, frass, and other drosophilids6,37. To
elucidate the role of environmentally-acquired microbes on
oogenesis, we first quantified mature eggs from “recipient” virgin
females placed in vials either sensitized (microbe-rich, M + ,
described later) with “donor” flies or left unsensitized (microbepoor, M-, described later). Flies were initially placed in vials for
3-4 days to ‘sensitize’ the vials and replaced with females exposed
to the vials for 3 days (Fig. 1a). Consistent with the larger ovary
size (Fig. 1b), females cultured in sensitized vials produced more
eggs at stage 13/14 than those in unsensitized vials (Fig. 1c). The
number of mature eggs (stage 13/14) were maximized when five
flies were used as donors in a single vial and after 3 days of
exposure for “recipient” females (Supplementary Fig. 1a, b).
These conditions were used for subsequent studies. Sensitized
females upon mating produced more progeny than those without
sensitization, but the hatching rate was comparable under both
conditions, suggesting that the quality of eggs from sensitized
females was unaffected (Supplementary Fig. 1c, d).
Both pheromones and microbes deposited by flies can contribute to
the oogenesis-promoting effect3,7,38. Several lines of evidence indicate
that microbes, rather than sex-specific pheromones, underlie oogenesis
enhancement. First, swab-wash eluate from sensitized vials was capable
of enhancing mature egg numbers, but the effect was abolished with
heat treatment (Supplementary Fig. 1e). Second, sensitizing vials with
either males or females increased egg production to a similar degree
(Supplementary Fig. 1f), indicating that the factors for enhancing egg
maturation are not sex-specific. Third, mutant females lacking
pheromone-responsive or chemo-sensitive receptors (Or83b, Wnt6a,
or Voila1)39,40 exhibit enhanced egg maturation when placed in
sensitized vials (Supplementary Fig. 1g). Lastly, vials sensitized with
pheromone extract from flies did not affect egg numbers (Supplementary Fig. 1h). These results suggest that heat-susceptible factors
other than sex-specific pheromones from “donor” flies were
responsible for enhancing egg development in “recipient” females.
To investigate whether acquired microbes enhance egg
maturation, we generated microbe-free flies (germ-free, GF)41
and examined their ability as donors to increase oogenesis.
Notably, female flies cultured in vials sensitized by GF flies had
fewer stage 13/14 eggs than those in vials sensitized by wildtype
laboratory-reared flies, and the number was similar to that of flies
placed in non-sensitized conditions (Fig. 1c). Indeed, we observed
a positive correlation between the numbers of microbes (as
measured by CFUs) and mature eggs induced by the donor flies
(Supplementary Fig. 1a, b, Supplementary Table 1). In addition,
no microbes were detected in germ free donor flies (Supplementary Table 1). Taken together, these findings indicate that
microbes or the metabolites from donor flies are responsible for
enhancing egg development in recipient female flies.
Acetobacter, the primary component of laboratory-reared fly
microbiomes, enhances oogenesis. To identify the genus of
microbes enhancing oogenesis, we performed 16S rRNA amplicon
sequencing on laboratory-reared flies used in our study. ...
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