Properties of ouabain-resistant ATPase from the excretory system of Poekilocerus bufonius

Al-Robai, Ali A.; Khoja, Samir M.; Al-Fifi, Zarraq

doi:10.1016/0020-1790(90)90084-8

Cited by 16 publications

(7 citation statements)

References 22 publications

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“…This contrasts sharply with the IC 50 of 3.98 × 10 −7 observed for the nervous tissue of P. bufonius [28] which again fits well with the IC 50 of 5.13 × 10 −7 of our brain copy mimic. The intermediate sensitivity of an IC 50 of 2 × 10 −4 reported by Al-Robai and co-workers [27] for hindgut plus Malpighian tubule preparations could in theory be caused by a combined expression of the two pyrgomorphid gene copies-this is, however, unlikely in the light of our RT-qPCR study that did not detect any brain copy expression in the midgut of P. aegrotus. On the other hand, the intermediate sensitivity might be caused by different combinations of αand β-subunits of the Na,K-ATPase.…”

Section: Discussioncontrasting

confidence: 47%

“…Specifically, we aimed to uncover whether resistance to cardiac glycosides repeats the same molecular patterns observed in other insect lineages. Furthermore, we used RT-qPCR to test whether differing tissue-specific expression patterns of the discovered alternative gene copies can explain the different sensitivities to cardiac glycosides of the gut, brain and excretory system of P. bufonius observed in the physiological studies of Al-Robai and coworkers [26][27][28]. Lastly, we introduced the substitutions and insertions observed in the first extracellular loop of the two pyrgomorphid Na,K-ATPase α genes into a Drosophila expression construct to demonstrate their functional effect on the enzyme's sensitivity to cardiac glycosides.…”

Section: Introductionmentioning

confidence: 99%

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New ways to acquire resistance: imperfect convergence in insect adaptations to a potent plant toxin

et al. 2019

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Evolution of insensitivity to the toxic effects of cardiac glycosides has become a model in the study of convergent evolution, as five taxonomic orders of insects use the same few similar amino acid substitutions in the otherwise highly conserved Na,K-ATPase α. We show here that insensitivity in pyrgomorphid grasshoppers evolved along a slightly divergent path. As in other lineages, duplication of the Na,K-ATPase α gene paved the way for subfunctionalization: one copy maintains the ancestral, sensitive state, while the other copy is resistant. Nonetheless, in contrast with all other investigated insects, the grasshoppers' resistant copy shows length variation by two amino acids in the first extracellular loop, the main part of the cardiac glycoside-binding pocket. RT-qPCR analyses confirmed that this copy is predominantly expressed in tissues exposed to the toxins, while the ancestral copy predominates in the nervous tissue. Functional tests with genetically engineered Drosophila Na,K-ATPases bearing the first extracellular loop of the pyrgomorphid genes showed the derived form to be highly resistant, while the ancestral state is sensitive. Thus, we report convergence in gene duplication and in the gene targets for toxin insensitivity; however, the means to the phenotypic end have been novel in pyrgomorphid grasshoppers.

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Section: Discussioncontrasting

confidence: 47%

Section: Introductionmentioning

confidence: 99%

New ways to acquire resistance: imperfect convergence in insect adaptations to a potent plant toxin

et al. 2019

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“…Enzyme assays first demonstrated that some of these species possess Na,K‐ATPases that are strongly resistant to the blocking effect of cardenolides (Vaughan and Jungreis ; Moore and Scudder ; Al‐Robai et al. ). As mutagenesis experiments in vertebrates revealed, such lowered sensitivity can be achieved by amino acid substitutions in the enzyme's binding pocket for cardenolides (Price and Lingrel ; Burns and Price ; Croyle et al.…”

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confidence: 99%

“…In many cases these insects even sequester the plant-derived toxins in their bodies for defense against their predators (Malcolm 1991;Dobler et al 2011;Petschenka et al 2011;Agrawal et al 2012;Petschenka and Agrawal 2016). Enzyme assays first demonstrated that some of these species possess Na,K-ATPases that are strongly resistant to the blocking effect of cardenolides (Vaughan and Jungreis 1977;Moore and Scudder 1986;Al-Robai et al 1990). As mutagenesis experiments in vertebrates revealed, such lowered sensitivity can be achieved by amino acid substitutions in the enzyme's binding pocket for cardenolides (Price and Lingrel 1988;Burns and Price 1993;Croyle et al 1997;Qiu et al 2005Qiu et al , 2006.…”

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confidence: 99%

Gene duplications circumvent trade-offs in enzyme function: Insect adaptation to toxic host plants

Dalla¹,

Dobler²

2016

Evolution

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Herbivorous insects and their adaptations against plant toxins provide striking opportunities to investigate the genetic basis of traits involved in coevolutionary interactions. Target site insensitivity to cardenolides has evolved convergently across six orders of insects, involving identical substitutions in the Na,K-ATPase gene and repeated convergent gene duplications. The large milkweed bug, Oncopeltus fasciatus, has three copies of the Na,K-ATPase α-subunit gene that bear differing numbers of amino acid substitutions in the binding pocket for cardenolides. To analyze the effect of these substitutions on cardenolide resistance and to infer possible trade-offs in gene function, we expressed the cardenolide-sensitive Na,K-ATPase of Drosophila melanogaster in vitro and introduced four distinct combinations of substitutions observed in the three gene copies of O. fasciatus. With an increasing number of substitutions, the sensitivity of the Na,K-ATPase to a standard cardenolide decreased in a stepwise manner. At the same time, the enzyme's overall activity decreased significantly with increasing cardenolide resistance and only the least substituted mimic of the Na,K-ATPase α1C copy maintained activity similar to the wild-type enzyme. Our results suggest that the Na,K-ATPase copies in O. fasciatus have diverged in function, enabling specific adaptations to dietary cardenolides while maintaining the functionality of this critical ion carrier.

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“…Insects in at least five orders (Diptera: Agromyzidae, Lepidoptera: Danaidae, Coleoptera: Chrysomelidae, Heteroptera: Lygaeidae, Sternorrhyncha: Aphididae, and Caelifera: Pyrgomorphidae) sequester and show adaptations to cope with cardenolides. These species possess a modified form of Na + /K + -ATPase that is resistant to cardenolides, due to a few amino acid substitutions, a phenomenon referred to as target site insensitivity [ 15 , 16 , 24 , 25 , 26 , 27 ]. In some cases, the evolution of this trait seems to be associated with the ability to sequester cardenolides for defense [ 28 ].…”

Section: Introductionmentioning

confidence: 99%

Defense of Milkweed Bugs (Heteroptera: Lygaeinae) against Predatory Lacewing Larvae Depends on Structural Differences of Sequestered Cardenolides

Pokharel

Sippel

Vilcinskas

et al. 2020

Insects

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Predators and parasitoids regulate insect populations and select defense mechanisms such as the sequestration of plant toxins. Sequestration is common among herbivorous insects, yet how the structural variation of plant toxins affects defenses against predators remains largely unknown. The palearctic milkweed bug Lygaeus equestris (Heteroptera: Lygaeinae) was recently shown to sequester cardenolides from Adonis vernalis (Ranunculaceae), while its relative Horvathiolus superbus also obtains cardenolides but from Digitalis purpurea (Plantaginaceae). Remarkably, toxin sequestration protects both species against insectivorous birds, but only H. superbus gains protection against predatory lacewing larvae. Here, we used a full factorial design to test whether this difference was mediated by the differences in plant chemistry or by the insect species. We raised both species of milkweed bugs on seeds from both species of host plants and carried out predation assays using the larvae of the lacewing Chrysoperla carnea. In addition, we analyzed the toxins sequestered by the bugs via liquid chromatography (HPLC). We found that both insect species gained protection by sequestering cardenolides from D. purpurea but not from A. vernalis. Since the total amount of toxins stored was not different between the plant species in H. superbus and even lower in L. equestris from D. purpurea compared to A. vernalis, the effect is most likely mediated by structural differences of the sequestered toxins. Our findings indicate that predator–prey interactions are highly context-specific and that the host plant choice can affect the levels of protection to various predator types based on structural differences within the same class of chemical compounds.

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Properties of ouabain-resistant ATPase from the excretory system of Poekilocerus bufonius

Cited by 16 publications

References 22 publications

New ways to acquire resistance: imperfect convergence in insect adaptations to a potent plant toxin

New ways to acquire resistance: imperfect convergence in insect adaptations to a potent plant toxin

Gene duplications circumvent trade-offs in enzyme function: Insect adaptation to toxic host plants

Defense of Milkweed Bugs (Heteroptera: Lygaeinae) against Predatory Lacewing Larvae Depends on Structural Differences of Sequestered Cardenolides

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