1
|
Reed KA, Williamson RT, Lee SG, Lee JH, Covi JA. Reversible intracellular acidification and depletion of NTPs provide a potential physiological origin for centuries of dormancy in an Antarctic freshwater copepod. Sci Rep 2023; 13:13243. [PMID: 37582969 PMCID: PMC10427605 DOI: 10.1038/s41598-023-40180-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 08/06/2023] [Indexed: 08/17/2023] Open
Abstract
A great diversity of crustacean zooplankton found in inland and coastal waters produce embryos that settle into bottom sediments to form an egg bank. Embryos from these banks can remain dormant for centuries, creating a reservoir of genetic diversity. A large body of literature describes the ecological and evolutionary importance of zooplankton egg banks. However, literature on the physiological traits behind dormancy in crustacean zooplankton are limited. Most data on the physiology of dormancy comes from research on one species of anostracan, the brine shrimp, Artemia franciscana. Anoxia-induced dormancy in this species is facilitated by a profound and reversible acidification of the intracellular space. This acidification is accompanied by a reversible depletion of adenosine triphosphate (ATP). The present study demonstrates that acidification of the intracellular space also occurs in concert with a depletion of nucleoside triphosphates (NTPs) in the Antarctic copepod, Boeckella poppei. Like A. franciscana, the depletion of NTPs and acidification are rapidly reversed during aerobic recovery in B. poppei. These data provide the first comparative evidence that extreme dormancy under anoxia in crustacean zooplankton is associated with intracellular acidification and an ability to recover from the depletion of ATP.
Collapse
Affiliation(s)
- Katherine A Reed
- Department of Biology and Marine Biology, The University of North Carolina at Wilmington, 601 S. College Rd., Wilmington, NC, 28403, USA
| | - R Thomas Williamson
- Department of Chemistry and Biochemistry, The University of North Carolina at Wilmington, 601 S. College Rd., Wilmington, NC, 28403, USA
| | - Sung Gu Lee
- Research Unit of Cryogenic Novel Material, Korea Polar Research Institute (KOPRI), Yeonsu-gu, Incheon, 21990, Korea
- Department of Polar Sciences, University of Science and Technology, Incheon, 21990, Korea
| | - Jun Hyuck Lee
- Research Unit of Cryogenic Novel Material, Korea Polar Research Institute (KOPRI), Yeonsu-gu, Incheon, 21990, Korea
- Department of Polar Sciences, University of Science and Technology, Incheon, 21990, Korea
| | - Joseph A Covi
- Department of Biology and Marine Biology, The University of North Carolina at Wilmington, 601 S. College Rd., Wilmington, NC, 28403, USA.
| |
Collapse
|
2
|
Callier V, Hand SC, Campbell JB, Biddulph T, Harrison JF. Developmental changes in hypoxic exposure and responses to anoxia in Drosophila melanogaster. J Exp Biol 2015. [DOI: 10.1242/jeb.125849] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Holometabolous insects undergo dramatic morphological and physiological changes during ontogeny. In particular, the larvae of many holometabolous insects are specialized to feed in soil, water or dung, inside plant structures, or inside other organisms as parasites where they may commonly experience hypoxia or anoxia. In contrast, holometabolous adults usually are winged and live with access to air. Here we show that larval Drosophila experience severe hypoxia in their normal laboratory environments; third instar larvae feed by tunneling into a medium without usable oxygen. Larvae move strongly in anoxia for many minutes, while adults (like most other adult insects) are quickly paralyzed. Adults survive anoxia nearly an order of magnitude longer than larvae (LT50: 8.3 vs. 1 h). Plausibly, the paralysis of adults is a programmed response to reduce ATP need and enhance survival. In support of that hypothesis, larvae produce lactate at 3x greater rates than adults in anoxia. However, when immobile in anoxia, larvae and adults were similarly able to decrease their metabolic rate in anoxia, to about 3% of normoxic conditions. These data suggest that Drosophila larvae and adults have been differentially selected for behavioral and metabolic responses to anoxia, with larvae exhibiting vigorous escape behavior likely enabling release from viscous anoxic media to predictably normoxic air, while the paralysis behavior of adults maximizes chances of survival of flooding events of unpredictable duration. Developmental remodeling of behavioral and metabolic strategies to hypoxia/anoxia is a previously unrecognized major attribute of holometabolism.
Collapse
Affiliation(s)
- Viviane Callier
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
| | - Steven C. Hand
- School of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Jacob B. Campbell
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
| | - Taylor Biddulph
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
| | - Jon F. Harrison
- School of Life Sciences, Arizona State University, Tempe, AZ 85287-4501, USA
| |
Collapse
|
3
|
Hand SC, Menze MA, Borcar A, Patil Y, Covi JA, Reynolds JA, Toner M. Metabolic restructuring during energy-limited states: insights from Artemia franciscana embryos and other animals. JOURNAL OF INSECT PHYSIOLOGY 2011; 57:584-94. [PMID: 21335009 PMCID: PMC3104064 DOI: 10.1016/j.jinsphys.2011.02.010] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Revised: 02/07/2011] [Accepted: 02/09/2011] [Indexed: 05/21/2023]
Abstract
Many life history stages of animals that experience environmental insults enter developmental arrested states that are characterized by reduced cellular proliferation, with or without a concurrent reduction in overall metabolism. In the case of the most profound metabolic arrest reported in invertebrates, i.e., anaerobic quiescence in Artemia franciscana embryos, acidification of the intracellular milieu is a major factor governing catabolic and anabolic downregulation. Release of ions from intracellular compartments is the source for approximately 50% of the proton equivalents needed for the 1.5 unit acidification that is observed. Recovery from the metabolic arrest requires re-sequestration of the protons with a vacuolar-type ATPase (V-ATPase). The remarkable facet of this mechanism is the ability of embryonic cells to survive the dissipation of intracellular ion gradients. Across many diapause-like states, the metabolic reduction and subsequent matching of energy demand is accomplished by shifting energy metabolism from oxidative phosphorylation to aerobic glycolysis. Molecular pathways that are activated to induce these resilient hypometabolic states include stimulation of the AMP-activated protein kinase (AMPK) and insulin signaling via suite of daf (dauer formation) genes for diapause-like states in nematodes and insects. Contributing factors for other metabolically depressed states involve hypoxia-inducible factor-1 and downregulation of the pyruvate dehydrogenase complex. Metabolic similarities between natural states of stasis and some cancer phenotypes are noteworthy. Reduction of flux through oxidative phosphorylation helps prevent cell death in certain cancer types, similar to the way it increases viability of dauer stages in Caenorhabditis elegans. Mechanisms that underlie natural stasis are being used to pre-condition mammalian cells prior to cell biostabilization and storage.
Collapse
Affiliation(s)
- Steven C Hand
- Division of Cellular, Developmental and Integrative Biology, Department of Biological, Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | | | | | | | | | | | | |
Collapse
|
4
|
Nambu Z, Tanaka S, Nambu F, Nakano M. Influence of darkness on embryonic diapause termination in dormantArtemiacysts with no experience of desiccation. ACTA ACUST UNITED AC 2009; 311:182-8. [DOI: 10.1002/jez.516] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
5
|
Covi JA, Hand SC. Energizing an Invertebrate Embryo: Bafilomycin‐Dependent Respiration and the Metabolic Cost of Proton Pumping by the V‐ATPase. Physiol Biochem Zool 2007; 80:422-32. [PMID: 17508337 DOI: 10.1086/518344] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/09/2007] [Indexed: 11/03/2022]
Abstract
We examine herein the contribution of V-ATPase activity to the energy budget of aerobically developing embryos of Artemia franciscana and discuss the results in the context of quiescence under anoxia. (31)P-NMR analysis indicates that intracellular pH and NTP levels are unaffected by acute incubation of dechorionated embryos with the V-ATPase inhibitor, bafilomycin A(1). Bafilomycin A(1) also has no significant effect on oxygen consumption by isolated mitochondria. Taken together, these data indicate that bafilomycin does not affect energy-producing pathways in the developing embryo. However, the V-ATPase inhibitor exhibits a concentration-dependent inhibition of oxygen consumption in aerobic embryos. A conservative analysis of respirometric data indicates that proton pumping by the V-ATPase, and processes immediately dependent on this activity, constitutes approximately 31% of the aerobic energy budget of the preemergent embryo. Given the complete absence of detectable Na(+)K(+)-ATPase activity during the first hours of aerobic development, it is plausible that the V-ATPase is performing a role in both the acidification of intracellular compartments and the energization of plasma membranes. Importantly, the high metabolic cost associated with maintaining these diverse proton gradients requires that V-ATPase activity be downregulated under anoxia in order to attain the almost complete metabolic depression observed in the quiescent embryo.
Collapse
Affiliation(s)
- Joseph A Covi
- Division of Cellular, Developmental, and Integrative Biology, Department of Biological Science, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
| | | |
Collapse
|
6
|
Warner AH, Clegg JS. Diguanosine nucleotide metabolism and the survival of artemia embryos during years of continuous anoxia. ACTA ACUST UNITED AC 2003. [DOI: 10.1046/j.1432-1327.2001.01993.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
|
7
|
Eads BD, Hand SC. Mitochondrial mRNA stability and polyadenylation during anoxia-induced quiescence in the brine shrimp Artemia franciscana. J Exp Biol 2003; 206:3681-92. [PMID: 12966060 DOI: 10.1242/jeb.00595] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Polyadenylation of messenger RNA is known to be an important mechanism for regulating mRNA stability in a variety of systems, including bacteria, chloroplasts and plant mitochondria. By comparison, little is known about the role played by polyadenylation in animal mitochondrial gene expression. We have used embryos of the brine shrimp Artemia franciscana to test hypotheses regarding message stability and polyadenylation under conditions simulating anoxia-induced quiescence. In response to anoxia, these embryos undergo a profound and acute metabolic downregulation, characterized by a steep drop in intracellular pH (pH(i)) and ATP levels. Using dot blots of total mitochondrial RNA, we show that during in organello incubations both O(2) deprivation and acidic pH (pH 6.4) elicit increases in half-lives of selected mitochondrial transcripts on the order of five- to tenfold or more, relative to normoxic controls at pH 7.8. Polyadenylation of these transcripts was measured under the same incubation conditions using a reverse transcriptase-polymerase chain reaction (RT-PCR)-based assay. The results demonstrate that low pH and anoxia promote significant deadenylation of the stabilized transcripts in several cases, measured either as change over time in the amount of polyadenylation within a given size class of poly(A)(+) tail, or as the total amount of polyadenylation at the endpoint of the incubation. This study is the first direct demonstration that for a metazoan mitochondrion, polyadenylation is associated with destabilized mRNA. This pattern has also been demonstrated in bacteria, chloroplasts and plant mitochondria and may indicate a conserved mechanism for regulating message half-life that differs from the paradigm for eukaryotic cytoplasm, where increased mRNA stability is associated with polyadenylation.
Collapse
Affiliation(s)
- Brian D Eads
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803 USA.
| | | |
Collapse
|
8
|
van Breukelen F, Maier R, Hand SC. Depression of nuclear transcription and extension of mRNA half-life under anoxia in Artemia franciscana embryos. J Exp Biol 2000; 203:1123-30. [PMID: 10708633 DOI: 10.1242/jeb.203.7.1123] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Transcriptional activity, as assessed by nuclear run-on assays, was constant during 10 h of normoxic development for embryos of the brine shrimp Artemia franciscana. Exposure of embryos to only 4 h of anoxia resulted in a 79.3+/−1 % decrease in levels of in-vivo-initiated transcripts, and transcription was depressed by 88. 2+/−0.7 % compared with normoxic controls after 24 h of anoxia (means +/− s.e.m., N=3). Initiation of transcription was fully restored after 1 h of normoxic recovery. Artificially lowering the intracellular pH of aerobic embryos to the value reflective of anoxia (pH 6.7) showed that acidification alone explained over half the transcriptional arrest. Initiation of transcription was not rescued by application of 80 % carbon monoxide under anoxia, which suggests that heme-based oxygen sensing is not involved in this global arrest. When these transcriptional data are combined with the finding that mRNA levels are unchanged for at least 6 h of anoxia, it is clear that the half-life of mRNA is extended at least 8.5-fold compared with that in aerobic embryos. In contrast to the activation of compensatory mechanisms to cope with anoxia that occurs in mammalian cells, A. franciscana embryos enter a metabolically depressed state in which gene expression and mRNA turnover are cellular costs apparently not compatible with survival and in which extended tolerance supercedes the requirement for continued metabolic function.
Collapse
Affiliation(s)
- F van Breukelen
- Section of Integrative Physiology and Neurobiology, Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, CO 80309-0334, USA
| | | | | |
Collapse
|
9
|
Eads BD, Hand SC. Regulatory features of transcription in isolated mitochondria from Artemia franciscana embryos. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:R1588-97. [PMID: 10600903 DOI: 10.1152/ajpregu.1999.277.6.r1588] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Optimal conditions were developed for an in organello transcriptional run-on assay using mitochondria isolated from Artemia franciscana embryos to investigate potential regulatory features of RNA synthesis under conditions of anoxia-induced quiescence. Transcription is not dependent on oxidative phosphorylation for maximal activity when exogenous ATP is available. Bona fide transcription products, as assessed by hybridization with specific mitochondrial cDNAs from A. franciscana, are produced in an inhibitor-sensitive manner. Transcription rate measured at pH 7.9 is reduced 80% when pH is lowered to 6.3, a pH range that mimics the in vivo change seen on exposure of embryos to anoxia. The proton sensitivity of mitochondrial RNA synthesis may provide a mechanism to depress this significant energy expenditure during quiescence. The influence of nucleotide concentration on kinetics is complicated by an interdependence among nucleotide species. ATP inhibition observed at subsaturating UTP concentrations is relieved when UTP is at saturating, physiologically relevant levels. Taken together, these data suggest that local (versus nuclear mediated) control is important in dictating mitochondrial transcription during rapid modulations in gene expression, such as those observed under anoxia-induced quiescence.
Collapse
Affiliation(s)
- B D Eads
- Department of Environmental, Population, and Organismic Biology, University of Colorado, Boulder, Colorado 80309-0334, USA
| | | |
Collapse
|