Abstract:Water intake is essential for survival and thus under strong regulation. Here, we describe a simple high throughput system to monitor water intake over time in Drosophila. The design of the assay involves dehydrating fly food and then adding water back separately so flies either eat or drink. Water consumption is then evaluated by weighing the water vessel and comparing this back to an evaporation control. Our system is high throughput, does not require animals to be artificially dehydrated, and is simple both… Show more
“…To differentiate the role of ITP in water versus food intake, we modified a recent method by Lau et al [19]. We reared flies on a medium poor in water (‘dry food’), and provided access to a separate, blue-dyed source of water (Fig 6A).…”
Section: Resultsmentioning
confidence: 99%
“…Nevertheless, insects, including Drosophila , can sense water [ 15 , 16 ] and exhibit hygrotactic behavior [ 17 , 18 ]. If given the opportunity, flies differentiate between food and water sources, and are able to seek and drink free water [ 19 , 20 ], or ingest media rich in water but devoid of nutrients [ 21 ]. Recently, a small group of neurons were identified in the Drosophila brain that antagonistically regulate thirst and hunger [ 22 ].…”
Animals need to continuously adjust their water metabolism to the internal and external conditions. Homeostasis of body fluids thus requires tight regulation of water intake and excretion, and a balance between ingestion of water and solid food. Here, we investigated how these processes are coordinated in Drosophila melanogaster. We identified the first thirst-promoting and anti-diuretic hormone of Drosophila, encoded by the gene Ion transport peptide (ITP). This endocrine regulator belongs to the CHH (crustacean hyperglycemic hormone) family of peptide hormones. Using genetic gain- and loss-of-function experiments, we show that ITP signaling acts analogous to the human vasopressin and renin-angiotensin systems; expression of ITP is elevated by dehydration of the fly, and the peptide increases thirst while repressing excretion, promoting thus conservation of water resources. ITP responds to both osmotic and desiccation stress, and dysregulation of ITP signaling compromises the fly’s ability to cope with these stressors. In addition to the regulation of thirst and excretion, ITP also suppresses food intake. Altogether, our work identifies ITP as an important endocrine regulator of thirst and excretion, which integrates water homeostasis with feeding of Drosophila.
“…To differentiate the role of ITP in water versus food intake, we modified a recent method by Lau et al [19]. We reared flies on a medium poor in water (‘dry food’), and provided access to a separate, blue-dyed source of water (Fig 6A).…”
Section: Resultsmentioning
confidence: 99%
“…Nevertheless, insects, including Drosophila , can sense water [ 15 , 16 ] and exhibit hygrotactic behavior [ 17 , 18 ]. If given the opportunity, flies differentiate between food and water sources, and are able to seek and drink free water [ 19 , 20 ], or ingest media rich in water but devoid of nutrients [ 21 ]. Recently, a small group of neurons were identified in the Drosophila brain that antagonistically regulate thirst and hunger [ 22 ].…”
Animals need to continuously adjust their water metabolism to the internal and external conditions. Homeostasis of body fluids thus requires tight regulation of water intake and excretion, and a balance between ingestion of water and solid food. Here, we investigated how these processes are coordinated in Drosophila melanogaster. We identified the first thirst-promoting and anti-diuretic hormone of Drosophila, encoded by the gene Ion transport peptide (ITP). This endocrine regulator belongs to the CHH (crustacean hyperglycemic hormone) family of peptide hormones. Using genetic gain- and loss-of-function experiments, we show that ITP signaling acts analogous to the human vasopressin and renin-angiotensin systems; expression of ITP is elevated by dehydration of the fly, and the peptide increases thirst while repressing excretion, promoting thus conservation of water resources. ITP responds to both osmotic and desiccation stress, and dysregulation of ITP signaling compromises the fly’s ability to cope with these stressors. In addition to the regulation of thirst and excretion, ITP also suppresses food intake. Altogether, our work identifies ITP as an important endocrine regulator of thirst and excretion, which integrates water homeostasis with feeding of Drosophila.
“…3D). At higher culture temperatures, flies consume more water and become dehydrated more easily 27 . Increasing age and dehydration in the setting of higher ambient temperatures are both known kidney stone risk factors in humans 28,29 .Figure 3Tubule calcium-phosphate deposits form in anterior tubules, increase with age and at high culture temperature.…”
How inorganic phosphate (Pi) homeostasis is regulated in
Drosophila
is currently unknown. We here identify
MFS
2 as a key Pi transporter in fly renal (Malpighian) tubules. Consistent with its role in Pi excretion, we found that dietary Pi induces
MFS2
expression. This results in the formation of Malpighian calcium-Pi stones, while RNAi-mediated knockdown of
MFS2
increases blood (hemolymph) Pi and decreases formation of Malpighian tubule stones in flies cultured on high Pi medium. Conversely, microinjection of adults with the phosphaturic human hormone
fibroblast growth factor 23
(
FGF23
) induces tubule expression of
MFS2
and decreases blood Pi. This action of
FGF23
is blocked by genetic ablation of
MFS2
. Furthermore, genetic overexpression of the fly
FGF branchless (bnl)
in the tubules induces expression of
MFS2
and increases Malpighian tubule stones suggesting that
bnl
is the endogenous phosphaturic hormone in adult flies. Finally, genetic ablation of
MFS2
increased fly life span, suggesting that Malpighian tubule stones are a key element whereby high Pi diet reduces fly longevity previously reported by us. In conclusion,
MFS2
mediates excretion of Pi in
Drosophila
, which is as in higher species under the hormonal control of
FGF-signaling
.
“…Since water is crucial for survival, flies memorize sensory cues associated with water with the help of dopamine: water information, similar to the presence of an attractive odorant (Lewis et al 2015 ), is conveyed by β'2 innervating DANs (Lin et al 2014 ). Moreover, a recent study reported that Dop1R1 mutant flies consumed less water compared to wild-type flies (Lau et al 2017 ). This study further showed that the palpability of water tasting increases because of dopamine release in thirsty animals (Lau 2017 ).…”
Section: Dans As Encoders Of State Context and Experiencementioning
confidence: 99%
“…Moreover, a recent study reported that Dop1R1 mutant flies consumed less water compared to wild-type flies (Lau et al 2017 ). This study further showed that the palpability of water tasting increases because of dopamine release in thirsty animals (Lau 2017 ). Through DANs, flies can also form short-term memory (STM) and LTM to cues associated with water.…”
Section: Dans As Encoders Of State Context and Experiencementioning
Behavioral flexibility for appropriate action selection is an advantage when animals are faced with decisions that will determine their survival or death. In order to arrive at the right decision, animals evaluate information from their external environment, internal state, and past experiences. How these different signals are integrated and modulated in the brain, and how context- and state-dependent behavioral decisions are controlled are poorly understood questions. Studying the molecules that help convey and integrate such information in neural circuits is an important way to approach these questions. Many years of work in different model organisms have shown that dopamine is a critical neuromodulator for (reward based) associative learning. However, recent findings in vertebrates and invertebrates have demonstrated the complexity and heterogeneity of dopaminergic neuron populations and their functional implications in many adaptive behaviors important for survival. For example, dopaminergic neurons can integrate external sensory information, internal and behavioral states, and learned experience in the decision making circuitry. Several recent advances in methodologies and the availability of a synaptic level connectome of the whole-brain circuitry of Drosophila melanogaster make the fly an attractive system to study the roles of dopamine in decision making and state-dependent behavior. In particular, a learning and memory center—the mushroom body—is richly innervated by dopaminergic neurons that enable it to integrate multi-modal information according to state and context, and to modulate decision-making and behavior.
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