Ontogenetic changes in digestive enzyme activities and the amino acid(AA) profile of starry flounder,Platichthys stellatus,were investigated and limiting amino acids were estimated compared with the essential AA profi...Ontogenetic changes in digestive enzyme activities and the amino acid(AA) profile of starry flounder,Platichthys stellatus,were investigated and limiting amino acids were estimated compared with the essential AA profile between larvae and live food to clarify starry flounder larval nutritional requirements.Larvae were collected at the egg stage and 0,2,4,7,12,17,24 days after hatching(DAH)for analysis.Larvae grew from 1.91 mm at hatching to 12.13 mm at 24 DAH.Trypsin and chymotrypsin activities changed slightly by 4 DAH and then increased significantly 4 DAH.Pepsin activity increased sharply beginning 17 DAH.Lipase activity increased significantly 4 DAH and increased progressively with larval growth.Amylase activity was also detected in newly hatched larvae and increased 7 DAH followed by a gradual decrease.High free amino acid(FAA) content was detected in starry flounder eggs(110.72mg/g dry weight).Total FAA content dropped to 43.29 mg/g in 4-DAH larvae and then decreased gradually to 13.74 mg/g in 24-DAH larvae.Most FAAs(except lysine and methionine) decreased >50%in 4-DAH larvae compared with those in eggs and then decreased to the lowest values in 24-DAH larvae.Changes in the protein amino acid(PAA) profile were much milder than those observed for FAAs.Most PAAs increased gradually during larval development,except lysine and phenylalanine.The percentages of free threonine,valine,isoleucine,and leucine decreased until the end of the trial,whereas the protein forms of these four AAs followed the opposite trend.A comparison of the essential AA composition of live food(rotifers,Artemia nauplii,and Artemia metanauplii) and larvae suggested that methionine was potentially the first limiting AA.These results may help develop starry flounder larviculture methods by solving the AA imbalance in live food.Moreover,the increased digestive enzyme activities indicate the possibility of introducing artificial compound feed.展开更多
Insects produce silk to form cocoons,nests,and webs,which are important for their survival and reproduction.However,little is known about the molecular mecha-nism of silk protein synthesis at the translation level.The...Insects produce silk to form cocoons,nests,and webs,which are important for their survival and reproduction.However,little is known about the molecular mecha-nism of silk protein synthesis at the translation level.The solute carrier family 7(SLC7)genes are involved in activating the target of rapamycin complex 1(TORC1)signaling pathway and protein translation process,but the physiological roles of SLC7 genes in silk-producing insects have not been reported.Here,we found that amino acid signaling regulates silk protein synthesis and larval development via the L-type amino acid trans-porter 1(LAT1;also known as SLC7A5)in Bombyx mori.A total of 12 SLC7 homologs were identified in the silkworm genome,among which BmSLC7A5 was found to be a silk gland-enriched gene and may be involved in leucine transport.Bioinformatics analy-sis indicated that SLC7A5 displays high homology and a close phylogenetic relationship in silk-producing insects.Subsequently,we found that leucine treatment significantly in-creased silk protein synthesis by improving the transcription and protein levels of silk genes.Furthermore,systemic and silk gland-specific knockout of BmSLC7A5 led to de-creased silk protein synthesis by inhibiting TORC1 signaling,and somatic mutation also resulted in arrested development from the 5th instar to the early pupal stage.Altogether,our study reveals that BmSLC7A5 is involved in regulating silk protein synthesis and larval development by affecting the TORC1 signaling pathway,which provides a new strategy and target for improving silk yield.展开更多
基金Supported by the Scientific and Technological Development Plan Project of Yantai City(No.2013ZH348)the Aquatic Animal Nutrition and Feed Research and Innovation Demonstration Platform(No.201301001)the National Special Research Fund for Non-Profit Marine Sector(No.1205025)
文摘Ontogenetic changes in digestive enzyme activities and the amino acid(AA) profile of starry flounder,Platichthys stellatus,were investigated and limiting amino acids were estimated compared with the essential AA profile between larvae and live food to clarify starry flounder larval nutritional requirements.Larvae were collected at the egg stage and 0,2,4,7,12,17,24 days after hatching(DAH)for analysis.Larvae grew from 1.91 mm at hatching to 12.13 mm at 24 DAH.Trypsin and chymotrypsin activities changed slightly by 4 DAH and then increased significantly 4 DAH.Pepsin activity increased sharply beginning 17 DAH.Lipase activity increased significantly 4 DAH and increased progressively with larval growth.Amylase activity was also detected in newly hatched larvae and increased 7 DAH followed by a gradual decrease.High free amino acid(FAA) content was detected in starry flounder eggs(110.72mg/g dry weight).Total FAA content dropped to 43.29 mg/g in 4-DAH larvae and then decreased gradually to 13.74 mg/g in 24-DAH larvae.Most FAAs(except lysine and methionine) decreased >50%in 4-DAH larvae compared with those in eggs and then decreased to the lowest values in 24-DAH larvae.Changes in the protein amino acid(PAA) profile were much milder than those observed for FAAs.Most PAAs increased gradually during larval development,except lysine and phenylalanine.The percentages of free threonine,valine,isoleucine,and leucine decreased until the end of the trial,whereas the protein forms of these four AAs followed the opposite trend.A comparison of the essential AA composition of live food(rotifers,Artemia nauplii,and Artemia metanauplii) and larvae suggested that methionine was potentially the first limiting AA.These results may help develop starry flounder larviculture methods by solving the AA imbalance in live food.Moreover,the increased digestive enzyme activities indicate the possibility of introducing artificial compound feed.
基金Thiswork was supported bygrants fromthe NationalNaturalScience FoundationofChina(31772532)the China Postdoctoral Science Foundation(2022MD713704)the Chongqing Science and Technology Bureau(cstc2021ljcyj-bshX0222 and jbky20210004).
文摘Insects produce silk to form cocoons,nests,and webs,which are important for their survival and reproduction.However,little is known about the molecular mecha-nism of silk protein synthesis at the translation level.The solute carrier family 7(SLC7)genes are involved in activating the target of rapamycin complex 1(TORC1)signaling pathway and protein translation process,but the physiological roles of SLC7 genes in silk-producing insects have not been reported.Here,we found that amino acid signaling regulates silk protein synthesis and larval development via the L-type amino acid trans-porter 1(LAT1;also known as SLC7A5)in Bombyx mori.A total of 12 SLC7 homologs were identified in the silkworm genome,among which BmSLC7A5 was found to be a silk gland-enriched gene and may be involved in leucine transport.Bioinformatics analy-sis indicated that SLC7A5 displays high homology and a close phylogenetic relationship in silk-producing insects.Subsequently,we found that leucine treatment significantly in-creased silk protein synthesis by improving the transcription and protein levels of silk genes.Furthermore,systemic and silk gland-specific knockout of BmSLC7A5 led to de-creased silk protein synthesis by inhibiting TORC1 signaling,and somatic mutation also resulted in arrested development from the 5th instar to the early pupal stage.Altogether,our study reveals that BmSLC7A5 is involved in regulating silk protein synthesis and larval development by affecting the TORC1 signaling pathway,which provides a new strategy and target for improving silk yield.
