(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/224832 doi: bioRxiv preprint first posted online 2
Abstract 22At low temperatures, Drosophila, like most insects, lose the ability to regulate ion and water 23 balance across the gut epithelia, which can lead to a lethal increase of [K + ] in the hemolymph 24 (hyperkalemia). Cold-acclimation, the physiological response to low temperature exposure, can 25 mitigate or entirely prevent these ion imbalances, but the physiological mechanisms that 26 facilitate this process are not well understood. Here, we test whether plasticity in the 27 ionoregulatory physiology of the gut and Malpighian tubules of Drosophila may aid in 28 preserving ion homeostasis in the cold. Upon adult emergence, D. melanogaster females were 29 subjected to seven days at warm (25°C) or cold (10°C) acclimation conditions. The cold 30 acclimated flies had a lower critical thermal minimum (CTmin), recovered from chill coma more 31 quickly, and better maintained hemolymph K + balance in the cold. The improvements in chill 32 tolerance coincided with increased Malpighian tubule fluid secretion and better maintenance of 33 K + secretion rates in the cold, as well as reduced rectal K + reabsorption in cold-acclimated flies. 34To test whether modulation of ion-motive ATPases, the main drivers of epithelial transport in the 35 alimentary canal, mediate these changes, we measured the activities of Na + -K + -ATPase and V-36 type H + -ATPase at the Malpighian tubules, midgut, and hindgut. Na + /K + -ATPase and V-type H + -37ATPase activities were lower in the midgut and the Malpighian tubules of cold-acclimated flies, 38 but unchanged in the hindgut of cold acclimated flies, and were not predictive of the observed 39 alterations in K + transport. Our results suggest that modification of Malpighian tubule and gut 40 ion and water transport likely prevents cold-induced hyperkalemia in cold-acclimated flies and 41 that this process is not directly related to the activities of the main drivers of ion transport in 42 these organs, Na + /K + -and V-type H + -ATPases. 43All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.