Transcription factors constitute numerous signal transduction networks and play a central role in gene expression regulation. Recent studies have shown that a limited portion of transcription factors are anchored in t...Transcription factors constitute numerous signal transduction networks and play a central role in gene expression regulation. Recent studies have shown that a limited portion of transcription factors are anchored in the cellular membrane, storing as dormant forms. Upon exposure to environmental and developmental cues, these transcription factors are released from the membrane and translocated to the nucleus, where they regulate associated target genes. As this process skips both transcriptional and translational regulations, it guarantees prompt response to external and internal signals. Membrane- bound transcription factors （MTFs） undergo several unique steps that are not involved in the action of canonical nuclear transcription factors： proteolytic processing and intracellular movement. Recently, alternative splicing has also emerged as a mechanism to liberate MTFs from the cellular membranes, establishing an additional activation scheme independent of proteolytic processing. Multiple layers of MTF regulation add complexity to transcriptional regulatory scheme and ensure elaborate action of MTFs. In this review, we provide an overview of recent findings on MTFs in plants and highlight the molecular mechanisms underlying MTF liberation from cellular membranes with an emphasis on intracellular movement.展开更多
The Arabidopsis （Arabidopsis thaliana L.） genome encodes for four distinct classes of homeodomain leucinezipper （HD-ZIP） transcription factors （HD-ZIPI to HD-ZIPIV）, which are all organized in multi-gene familie...The Arabidopsis （Arabidopsis thaliana L.） genome encodes for four distinct classes of homeodomain leucinezipper （HD-ZIP） transcription factors （HD-ZIPI to HD-ZIPIV）, which are all organized in multi-gene families. HD-ZIP transcription factors act as sequence-specific DNA-binding proteins that are able to control the expression level of target genes. While HD-ZIPI and HD-ZIPII proteins are mainly associated with environmental responses, HD-ZIPIII and HD- ZIPIV are primarily known to act as patterning factors. Recent studies have challenged this view. It appears that several of the different HD-ZlP families interact genetically to align both morphogenesis and environmental responses, most likely by modulating phytohormone-signaling networks.展开更多
This experiment was to investigate the effects of dietary leucine supplementation on the gene expression of mammalian target of rapamycin(mTOR) signaling pathway and intestinal development of broilers. A total of 384 ...This experiment was to investigate the effects of dietary leucine supplementation on the gene expression of mammalian target of rapamycin(mTOR) signaling pathway and intestinal development of broilers. A total of 384 one-day-old broilers were randomly assigned into 4 treatments with 6 replicates(16 broilers per replicate). Broilers in these treatment groups were offered the following diets with 1.37,1.77,2.17 and2.57% of leucine. These diet treatments were named 1.37 TM, 1.77 TM, 2.17 TM, and 2.57 TM. The experiment lasted 21 days and all birds had free access to feed and water. Results indicated that there was no significant difference in body weight, average daily gain and average feed intake among all treatments(P > 0.05). The broiler duodenal villus height in 2.57 TM was the lowest, but the highest occurred in1.37 TM on d 7 and 14(P < 0.05). The villus height in the jejunum and ileum increased along with leucine level from 1.37 to 2.17%. The villus height of jejunum was significantly higher in 2.17 TM than in 1.37 TM on d 7 and 14, and the ratio of villus height to crypt depth(V:C) in the duodenum, jejunum and ileum increased significantly(P < 0.05) on d 21. The gene expression level of mTOR in the duodenum decreased with increasing leucine level and was higher in 1.37 TM than in 2.57 TM on d 7 and 14(P < 0.05). On d 14 and 21 of the trial, the expression of S6 K1 in the duodenum was higher in 1.37 TM than in 2.57 TM(P < 0.05), and the expression of mTOR, S6 K1 in the jejunum and ileum increased with increasing leucine level form 1.37 to 2.17%, whereas a significant difference occurred between 1.37 TM and 2.17 TM(P< 0.05).In conclusion, the addition of leucine fails to enhance the growth performance of broilers. However,leucine can improve intestinal development by enhancing villus height and V:C ratio in the jejunum and ileum. Moreover, the expression of mTOR, S6 K1 increased as the level of dietary leucine was elevated from 1.37 to 2.17%.展开更多
Neonatal growth is characterized by a high protein synthesis rate that is largely due to an enhanced sensitivity to the postprandial rise in insulin and amino acids, especially leucine. The mechanism of leucine＇s act...Neonatal growth is characterized by a high protein synthesis rate that is largely due to an enhanced sensitivity to the postprandial rise in insulin and amino acids, especially leucine. The mechanism of leucine＇s action in vivo is not well understood. In this study, we investigated the effect of leucine infusion on protein synthesis in skeletal muscle and liver of neonatal pigs. To evaluate the mode of action of leucine, we used rapamycin, an inhibitor of mammalian target of rapamycin （mTOR） complex-1 （mTORC1）. Overnight-fasted 7-day-old piglets were treated with rapamycin for 1 hour and then infused with leucine （400 μmol·kg^-1·h^-1） for 1 hour. Leucine infusion increased the rate of protein synthesis, and ribosomal protein S6 kinase 1 （S6K1） and eukaryotic initiation factor （elF） 4E-binding protein-1 （4E-BP1） phosphorylation in gastrocnemius and masseter muscles （P 〈 0.05）, but not in the liver. The leucine-induced stimulation of protein synthesis and S6K1 and 4E-BP1 phosphorylation were completely blocked by rapamycin, suggesting that leucine action is by an mTORC1-dependent mechanism. Neither leucine nor rapamycin had any effect on the activation of the upstream mTQRC1 regulators, AMP-activated protein kinase and protein kinase B, in skeletal muscle or liver. The activation of elF2α and elongation factor 2 was not affected by leucine or rapamycin, indicating that these two pathways are not limiting steps of leucine-induced protein synthesis. These results suggest that leucine stimulates muscle protein synthesis in neonatal pigs by inducing the activation of mTORC1 and its downstream pathway leading to mRNA translation.展开更多
基金supported by Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Education(NRF-2013R1A1A1004831)research funds of Chonbuk National University in 2012
文摘Transcription factors constitute numerous signal transduction networks and play a central role in gene expression regulation. Recent studies have shown that a limited portion of transcription factors are anchored in the cellular membrane, storing as dormant forms. Upon exposure to environmental and developmental cues, these transcription factors are released from the membrane and translocated to the nucleus, where they regulate associated target genes. As this process skips both transcriptional and translational regulations, it guarantees prompt response to external and internal signals. Membrane- bound transcription factors （MTFs） undergo several unique steps that are not involved in the action of canonical nuclear transcription factors： proteolytic processing and intracellular movement. Recently, alternative splicing has also emerged as a mechanism to liberate MTFs from the cellular membranes, establishing an additional activation scheme independent of proteolytic processing. Multiple layers of MTF regulation add complexity to transcriptional regulatory scheme and ensure elaborate action of MTFs. In this review, we provide an overview of recent findings on MTFs in plants and highlight the molecular mechanisms underlying MTF liberation from cellular membranes with an emphasis on intracellular movement.
基金funded by the Deutsche Forschungsgemeinschaft, an International Reintegration Grant of the European Union, the European Research Council and the German Ministry for Agriculture
文摘The Arabidopsis （Arabidopsis thaliana L.） genome encodes for four distinct classes of homeodomain leucinezipper （HD-ZIP） transcription factors （HD-ZIPI to HD-ZIPIV）, which are all organized in multi-gene families. HD-ZIP transcription factors act as sequence-specific DNA-binding proteins that are able to control the expression level of target genes. While HD-ZIPI and HD-ZIPII proteins are mainly associated with environmental responses, HD-ZIPIII and HD- ZIPIV are primarily known to act as patterning factors. Recent studies have challenged this view. It appears that several of the different HD-ZlP families interact genetically to align both morphogenesis and environmental responses, most likely by modulating phytohormone-signaling networks.
基金supported by China Agriculture Research System(CARS-42)
文摘This experiment was to investigate the effects of dietary leucine supplementation on the gene expression of mammalian target of rapamycin(mTOR) signaling pathway and intestinal development of broilers. A total of 384 one-day-old broilers were randomly assigned into 4 treatments with 6 replicates(16 broilers per replicate). Broilers in these treatment groups were offered the following diets with 1.37,1.77,2.17 and2.57% of leucine. These diet treatments were named 1.37 TM, 1.77 TM, 2.17 TM, and 2.57 TM. The experiment lasted 21 days and all birds had free access to feed and water. Results indicated that there was no significant difference in body weight, average daily gain and average feed intake among all treatments(P > 0.05). The broiler duodenal villus height in 2.57 TM was the lowest, but the highest occurred in1.37 TM on d 7 and 14(P < 0.05). The villus height in the jejunum and ileum increased along with leucine level from 1.37 to 2.17%. The villus height of jejunum was significantly higher in 2.17 TM than in 1.37 TM on d 7 and 14, and the ratio of villus height to crypt depth(V:C) in the duodenum, jejunum and ileum increased significantly(P < 0.05) on d 21. The gene expression level of mTOR in the duodenum decreased with increasing leucine level and was higher in 1.37 TM than in 2.57 TM on d 7 and 14(P < 0.05). On d 14 and 21 of the trial, the expression of S6 K1 in the duodenum was higher in 1.37 TM than in 2.57 TM(P < 0.05), and the expression of mTOR, S6 K1 in the jejunum and ileum increased with increasing leucine level form 1.37 to 2.17%, whereas a significant difference occurred between 1.37 TM and 2.17 TM(P< 0.05).In conclusion, the addition of leucine fails to enhance the growth performance of broilers. However,leucine can improve intestinal development by enhancing villus height and V:C ratio in the jejunum and ileum. Moreover, the expression of mTOR, S6 K1 increased as the level of dietary leucine was elevated from 1.37 to 2.17%.
文摘Neonatal growth is characterized by a high protein synthesis rate that is largely due to an enhanced sensitivity to the postprandial rise in insulin and amino acids, especially leucine. The mechanism of leucine＇s action in vivo is not well understood. In this study, we investigated the effect of leucine infusion on protein synthesis in skeletal muscle and liver of neonatal pigs. To evaluate the mode of action of leucine, we used rapamycin, an inhibitor of mammalian target of rapamycin （mTOR） complex-1 （mTORC1）. Overnight-fasted 7-day-old piglets were treated with rapamycin for 1 hour and then infused with leucine （400 μmol·kg^-1·h^-1） for 1 hour. Leucine infusion increased the rate of protein synthesis, and ribosomal protein S6 kinase 1 （S6K1） and eukaryotic initiation factor （elF） 4E-binding protein-1 （4E-BP1） phosphorylation in gastrocnemius and masseter muscles （P 〈 0.05）, but not in the liver. The leucine-induced stimulation of protein synthesis and S6K1 and 4E-BP1 phosphorylation were completely blocked by rapamycin, suggesting that leucine action is by an mTORC1-dependent mechanism. Neither leucine nor rapamycin had any effect on the activation of the upstream mTQRC1 regulators, AMP-activated protein kinase and protein kinase B, in skeletal muscle or liver. The activation of elF2α and elongation factor 2 was not affected by leucine or rapamycin, indicating that these two pathways are not limiting steps of leucine-induced protein synthesis. These results suggest that leucine stimulates muscle protein synthesis in neonatal pigs by inducing the activation of mTORC1 and its downstream pathway leading to mRNA translation.
