Anti-diuretic activity of a CAPA neuropeptide can compromiseDrosophilachill tolerance

Abstract

Statement: Many insects ion balance in the cold. We show how one 26 neuropeptide can slow ion transport and reduce the cold tolerance of a fly. 27 28 29 30 Abstract 31For insects, chilling injuries that occur in the absence of freezing are often related to a 32 systemic loss of ion and water balance that leads to extracellular hyperkalemia, cell 33 depolarization, and the triggering of apoptotic signalling cascades. The ability of insect 34 ionoregulatory organs (e.g. the Malpighian tubules) to maintain ion balance in the cold has been 35 linked to improved chill tolerance, and many neuroendocrine factors are known to influence ion 36 transport rates of these organs. Injection of micromolar doses of CAPA (an insect neuropeptide) 37 have been previously demonstrated to improve Drosophila cold tolerance, but the mechanisms 38 through which it impacts chill tolerance are unclear, and low doses of CAPA have been 39 demonstrated to cause anti-diuresis in other insects, including dipterans. Here, we provide 40 evidence that low (fM) and high (µM) doses of CAPA impair and improve chill tolerance, 41 respectively, via two different effects on Malpighian tubule ion and water transport. While low 42 doses of CAPA are anti-diuretic, reduce tubule K + clearance rates and reduce chill tolerance, 43 high doses facilitate K + clearance from the haemolymph and increase chill tolerance. By 44 quantifying CAPA peptide levels in the central nervous system, we estimated the maximum 45 achievable hormonal titres of CAPA, and found evidence to suggest that CAPA may function as 46 an anti-diuretic peptide in Drosophila. We provide the first evidence of a neuropeptide that can 47 negatively affect cold tolerance in an insect, and the first evidence of CAPA as an anti-diuretic 48 peptide in this ubiquitous insect model. 49 et al., 2017a;Djamgoz, 1987; MacMillan et al., 2014;Rheuben, 1972). Over minutes to hours, 64 suppressed ion transport allows for the net movement of Na + and water down their concentration 65 50

A neuroendocrine pathway modulating osmotic stress inDrosophila

“…Hence, to address this, we examine the role of Crz in modulating osmotic and ionic stresses and furthermore outline the cellular systems constituting the Crz signaling axis. To this end, we analyzed the effects of manipulating Crz signaling on desiccation tolerance and chill-coma recovery as these two assays are routinely used to assess responses to osmotic/ionic stress (26, 27). Both knockdown of Crz and acute injections of Crz peptide impact desiccation tolerance and recovery from chill-coma.…”

Warm periods in repeated cold stresses protectDrosophilaagainst ionoregulatory collapse, chilling injury, and reproductive deficits

“…After a group had accumulated 25 h of exposure to 0°C, the flies were moved to food vials and placed in the incubator for 24 h. The degree of injury/survival of each fly was then assessed using a modified four-point scale similar to that described previously (MacMillan et al, 2018). Briefly, a fly was scored as a 1 if it was dead; a 2 if it was able to stand upright but not walk; a 3 if it was able to walk on the food surface but not climb the vial walls; and a 4 if it displayed baseline, pre-chilling behaviour by jumping, walking, and climbing inside the vial.…”

Impact of high-fat diet on lifespan, metabolism, fecundity and behavioral senescence inDrosophila

“…Insects, including Drosophila, respond to prolonged cold by entering a coma-like state and after transfer to normal temperature they recover (Overgaard and MacMillan, 2017;Sinclair et al, 2013). The time it takes to recover from chill coma is used as a measure of cold tolerance and general stress resistance (MacMillan et al, 2018;Overgaard and MacMillan, 2017;Terhzaz et al, 2015). We monitored the recovery time from chill coma in mated female flies after eight days of exposure to 10% and 30% HFD and ND (Supplemental Fig.…”