Hyoscyamine, anisodamine and scopolamine are tropane alkaloids present in some Solanaceae species and used in modern medicine. L-Hyoscyamine is hydroxylated to 6</span><i><span style="font-family:V...Hyoscyamine, anisodamine and scopolamine are tropane alkaloids present in some Solanaceae species and used in modern medicine. L-Hyoscyamine is hydroxylated to 6</span><i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-hydroxyhyoscyamine (anisodamine) and then epoxidated to scopolamine by the dual action of hyoscyamine 6</span><i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-hydroxylase (H6H), a 2-o</span><span><span style="font-family:Verdana;">xoglutarate dependent dioxygenase. A natural mutation in the Gly-220 residue to Cys was previously shown to be associated with the loss of function of H6H in </span><i><span style="font-family:Verdana;">Mandragora</span></i> <i><span style="font-family:Verdana;">officinarum</span></i><span style="font-family:Verdana;">, preventing the accumulation of anisodamin</span></span><span style="font-family:Verdana;">e and scopolamine in these plants. We show here that a deliberate Gly220Cys mutation in the </span><i><span style="font-family:Verdana;">Datura innoxia</span></i><span style="font-family:Verdana;"> DiH6H protein caused a loss of both its enzymatic abilities and rendered it unable to hydroxylate L-hyoscyamine into anisodamine and to epoxidate anisodamine into scopolamine. By using protein modeling based on an available crystal structure of H6H from </span><i><span style="font-family:Verdana;">Datura metel</span></i><span style="font-family:Verdana;">, we show how the Cys220 residue causes a steric interference in the active site cavity impairing the interaction of both substrates, hyoscyamine and anisodamine with the active site of the protein</span></span><span style="font-family:Verdana;">.</span><span style="font-family:Verdana;"> We also address the enantiomeric preference of DiH6H based on molecular modeling.展开更多
The diet of ungulates is often characterized by low protein levels and the presence of indigestible and defensive compounds.It also often lacks micronutrients(vitamins and minerals)essential for growth,health and repr...The diet of ungulates is often characterized by low protein levels and the presence of indigestible and defensive compounds.It also often lacks micronutrients(vitamins and minerals)essential for growth,health and reproduction.Ungulates select rich plant organs to compensate for nutrient shortages and may consume soil,faeces and even bones.It is common for ungulates to incidentally ingest plant-dwelling insects(PDI)while feeding.It is well known that insects contain protein and essential nutrients that can feed livestock,potentially replacing conventional feed.Based on this,we propose the‘nutritional benefit of incidental ingestion'hypothesis,suggesting that ungulates may nutritionally benefit from ingesting PDI while foraging.Based on evidence from the literature on PDI ingestion by ungulates and on the nutritional properties of different insects,we discuss how and whether the ingestion of PDI while foraging might improve the nutrient balance of ungulates and recommend a set of controlled experiments to test it.We provide a new and unfamiliar dimension of nutritional ecology,which is relevant to various grazing ecosystems.We propose to modify“trivial”food web structures,as direct trophic interactions between ungulates and PDI may hold greater significance for ungulate performance and behaviour.展开更多
Aims Acorn weevils(Curculio spp.),endoparasitic granivorous insects,impede recruitment of fagaceous trees,and in turn affect community structure and ecosystem functioning.Previous studies have made considerable progre...Aims Acorn weevils(Curculio spp.),endoparasitic granivorous insects,impede recruitment of fagaceous trees,and in turn affect community structure and ecosystem functioning.Previous studies have made considerable progress in elucidating local factors that contribute to seed predation by acorn weevils,but it is still not clear how habitat configurations interplay with local factors in influencing Curculio predation.In this study,we assessed the roles of crop size,landscape configurations(area and isolation)and their interactions on the predation rate of seeds by acorn weevils.Methods We studied acorn weevils feeding on the seeds of Castanopsis sclerophylla(Fagaceae)on two peninsulas and nine islands with varying areas and isolation levels in the Thousand-island Lake in Chun’an County,Zhejiang Province of China.Overall,crop size was estimated for 130 trees and predation status was assessed for 26207 seeds from these trees during two years.Generalized linear mixed models were performed to clarify how island area and isolation interplayed with crop size to determine predation rate on a single tree.Important Findings A negative relationship was detected between crop size and seed predation rate,indicating predator satiation at the tree level.This suggests that acorn weevils tend to stay sedentary once they have arrived at a suitable habitat.Habitat fragmentation had significant effects on seed predation such that predation rate was higher on larger,less isolated islands.Furthermore,the relationship between crop size and predation rate was significantly changed by both island area and isolation.This finding highlighted that the effects of habitat isolation might be overlooked relative to those of habitat loss.展开更多
When forced to drop from the plant,flightless arboreal insects can avoid reaching the risky ground by maneuvering their body through the air.When wingless pea aphids(Acyrthosiphon pisum)are threatened by natural enemi...When forced to drop from the plant,flightless arboreal insects can avoid reaching the risky ground by maneuvering their body through the air.When wingless pea aphids(Acyrthosiphon pisum)are threatened by natural enemies,they often drop off their host plant while assuming a stereotypic posture that rotates them in mid-air,aligning them with their feet pointing downwards.This position may increase their chances of re-clinging onto lower plant parts and avoid facing the dangers on the ground,although its effectiveness in realistic field conditions has not been tested.We performed both laboratory and outdoor experiments,in which we dropped aphids upon host plants to quantify clinging success in plants with different characteristics such as height and leaf size.Live aphids had twofold higher clinging rates than dead ones,indicating that clinging success is indeed affected by the active aerial-righting of dropping aphids.The ability to cling was positively dependent on the plants’foliage cover as viewed in vertical direction from above.Therefore,we released aphids in commercial alfalfa(Medicago sativa)fields with varying plant heights and foliage cover and induced them to drop.Most(up to 75%)of the aphids avoided reaching the ground in taller plants(65 cm),and 17%in shorter plants(21 cm),demonstrating the efficiency of the aphids’response in averting risks:both those of an approaching enemy on the plant and the plethora of new risks on the ground.Evidently,even in complex field environment,the aerial-righting mechanism can substantially reduce the possible risks following escape from a predator.展开更多
文摘Hyoscyamine, anisodamine and scopolamine are tropane alkaloids present in some Solanaceae species and used in modern medicine. L-Hyoscyamine is hydroxylated to 6</span><i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-hydroxyhyoscyamine (anisodamine) and then epoxidated to scopolamine by the dual action of hyoscyamine 6</span><i><span style="font-family:Verdana;">β</span></i><span style="font-family:Verdana;">-hydroxylase (H6H), a 2-o</span><span><span style="font-family:Verdana;">xoglutarate dependent dioxygenase. A natural mutation in the Gly-220 residue to Cys was previously shown to be associated with the loss of function of H6H in </span><i><span style="font-family:Verdana;">Mandragora</span></i> <i><span style="font-family:Verdana;">officinarum</span></i><span style="font-family:Verdana;">, preventing the accumulation of anisodamin</span></span><span style="font-family:Verdana;">e and scopolamine in these plants. We show here that a deliberate Gly220Cys mutation in the </span><i><span style="font-family:Verdana;">Datura innoxia</span></i><span style="font-family:Verdana;"> DiH6H protein caused a loss of both its enzymatic abilities and rendered it unable to hydroxylate L-hyoscyamine into anisodamine and to epoxidate anisodamine into scopolamine. By using protein modeling based on an available crystal structure of H6H from </span><i><span style="font-family:Verdana;">Datura metel</span></i><span style="font-family:Verdana;">, we show how the Cys220 residue causes a steric interference in the active site cavity impairing the interaction of both substrates, hyoscyamine and anisodamine with the active site of the protein</span></span><span style="font-family:Verdana;">.</span><span style="font-family:Verdana;"> We also address the enantiomeric preference of DiH6H based on molecular modeling.
文摘The diet of ungulates is often characterized by low protein levels and the presence of indigestible and defensive compounds.It also often lacks micronutrients(vitamins and minerals)essential for growth,health and reproduction.Ungulates select rich plant organs to compensate for nutrient shortages and may consume soil,faeces and even bones.It is common for ungulates to incidentally ingest plant-dwelling insects(PDI)while feeding.It is well known that insects contain protein and essential nutrients that can feed livestock,potentially replacing conventional feed.Based on this,we propose the‘nutritional benefit of incidental ingestion'hypothesis,suggesting that ungulates may nutritionally benefit from ingesting PDI while foraging.Based on evidence from the literature on PDI ingestion by ungulates and on the nutritional properties of different insects,we discuss how and whether the ingestion of PDI while foraging might improve the nutrient balance of ungulates and recommend a set of controlled experiments to test it.We provide a new and unfamiliar dimension of nutritional ecology,which is relevant to various grazing ecosystems.We propose to modify“trivial”food web structures,as direct trophic interactions between ungulates and PDI may hold greater significance for ungulate performance and behaviour.
基金National Natural Science Foundation of China(31361123001)National Science Foundation(DEB-1342751 and DEB-1342757).
文摘Aims Acorn weevils(Curculio spp.),endoparasitic granivorous insects,impede recruitment of fagaceous trees,and in turn affect community structure and ecosystem functioning.Previous studies have made considerable progress in elucidating local factors that contribute to seed predation by acorn weevils,but it is still not clear how habitat configurations interplay with local factors in influencing Curculio predation.In this study,we assessed the roles of crop size,landscape configurations(area and isolation)and their interactions on the predation rate of seeds by acorn weevils.Methods We studied acorn weevils feeding on the seeds of Castanopsis sclerophylla(Fagaceae)on two peninsulas and nine islands with varying areas and isolation levels in the Thousand-island Lake in Chun’an County,Zhejiang Province of China.Overall,crop size was estimated for 130 trees and predation status was assessed for 26207 seeds from these trees during two years.Generalized linear mixed models were performed to clarify how island area and isolation interplayed with crop size to determine predation rate on a single tree.Important Findings A negative relationship was detected between crop size and seed predation rate,indicating predator satiation at the tree level.This suggests that acorn weevils tend to stay sedentary once they have arrived at a suitable habitat.Habitat fragmentation had significant effects on seed predation such that predation rate was higher on larger,less isolated islands.Furthermore,the relationship between crop size and predation rate was significantly changed by both island area and isolation.This finding highlighted that the effects of habitat isolation might be overlooked relative to those of habitat loss.
文摘When forced to drop from the plant,flightless arboreal insects can avoid reaching the risky ground by maneuvering their body through the air.When wingless pea aphids(Acyrthosiphon pisum)are threatened by natural enemies,they often drop off their host plant while assuming a stereotypic posture that rotates them in mid-air,aligning them with their feet pointing downwards.This position may increase their chances of re-clinging onto lower plant parts and avoid facing the dangers on the ground,although its effectiveness in realistic field conditions has not been tested.We performed both laboratory and outdoor experiments,in which we dropped aphids upon host plants to quantify clinging success in plants with different characteristics such as height and leaf size.Live aphids had twofold higher clinging rates than dead ones,indicating that clinging success is indeed affected by the active aerial-righting of dropping aphids.The ability to cling was positively dependent on the plants’foliage cover as viewed in vertical direction from above.Therefore,we released aphids in commercial alfalfa(Medicago sativa)fields with varying plant heights and foliage cover and induced them to drop.Most(up to 75%)of the aphids avoided reaching the ground in taller plants(65 cm),and 17%in shorter plants(21 cm),demonstrating the efficiency of the aphids’response in averting risks:both those of an approaching enemy on the plant and the plethora of new risks on the ground.Evidently,even in complex field environment,the aerial-righting mechanism can substantially reduce the possible risks following escape from a predator.
