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Tao C, Li J, Du W, Qin X, Cao J, Liu C, Cheng T. Broad Complex-Z2 directly activates BmMBF2 to inhibit the silk protein synthesis in the silkworm, Bombyx mori. Int J Biol Macromol 2024; 277:134211. [PMID: 39069049 DOI: 10.1016/j.ijbiomac.2024.134211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2024] [Revised: 06/27/2024] [Accepted: 07/25/2024] [Indexed: 07/30/2024]
Abstract
Silk proteins, as natural macromolecules, have extensive applications in biomaterials and biomedicine. In the silkworm, the expression of silk protein genes is negatively associated with ecdysone during the molt stage, while it is positively correlated with juvenile hormone during the intermolt stage. In our previous study, overexpression of an isoform Z2 of Broad Complex (BmBrC-Z2), an ecdysone early response factor, significantly reduced the expression of silk protein genes. However, the underlying regulatory mechanism remains unclear. In this study, we conducted transcriptomic analysis and found that overexpressing BmBrC-Z2 significantly upregulated the expression level of multiprotein bridging factor 2 (BmMBF2), an inhibitor of fibroin heavy chain (FibH). Further investigations revealed that BmBrC-Z2 directly regulated BmMBF2 by binding to cis-regulatory elements, as demonstrated using Dual-Luciferase Reporter Gene Assay, EMSA, and ChIP-PCR assay. Additionally, when using the CRISPR/Cas9 system to knock out BmMBF2, silk protein genes were significantly upregulated during the molt stage of mutant larvae. These findings uncover the negative regulation of silk protein synthesis by the ecdysone signaling cascade, specifically through the manipulation of BmMBF2 expression during the molt stage. This study enhances to our understanding of the temporal regulatory mechanism governing silk protein synthesis and offers a potential strategy for improving silk yield.
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Affiliation(s)
- Cuicui Tao
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China
| | - Jiaojiao Li
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China
| | - Wenjie Du
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China
| | - Xiaodan Qin
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China
| | - Jun Cao
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China
| | - Chun Liu
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China.
| | - Tingcai Cheng
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400715, China.
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2
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Cao J, Tao C, Qin X, Wu K, Yang H, Liu C, Cheng T. PI3K-Akt-SGF1-Dimm pathway mediates the nutritional regulation of silk protein synthesis in Bombyx mori. Int J Biol Macromol 2024; 278:134650. [PMID: 39128739 DOI: 10.1016/j.ijbiomac.2024.134650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2024] [Revised: 08/04/2024] [Accepted: 08/08/2024] [Indexed: 08/13/2024]
Abstract
The efficient synthesis of silk protein is heavily reliant on the ingestion of massive nutrients during the peak growth phase in the silkworm. However, the molecular mechanism of nutritional regulation of silk protein synthesis remains unknown. In this study, we investigated the impact of nutrient deficiency on the synthesis of silk protein. Nutritional deficiency led to a reduction in silk yield, accompanied by decreased levels of silk proteins and fibroin heavy chain (FibH)-activating transcription factors SGF1 and Dimm. Furthermore, insulin enhanced the protein levels of SGF1 and Dimm, which can be attenuated by specific inhibitors of PI3K. Co-immunoprecipitation analysis showed that the nutrient pathway factor protein kinase B (Akt) could interact with SGF1 protein. Knockdown of Akt reduced the phosphorylation level of SGF1 and impedes its nuclear translocation. Further studies revealed that SGF1 was directly bound to Fkh site in the 22-43 region upstream of ATG of Dimm gene to activate its transcription. In conclusion, during the peak growth phase, nutrition promotes the massive synthesis of silk protein through the PI3K-Akt-SGF1-Dimm pathway. This study offers valuable insights into the efficient synthesis of silk proteins and establishes a theoretical foundation for improving silk yield.
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Affiliation(s)
- Jun Cao
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400716, China
| | - Cuicui Tao
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400716, China
| | - Xiaodan Qin
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400716, China
| | - Keli Wu
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400716, China
| | - Hongguo Yang
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400716, China
| | - Chun Liu
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400716, China.
| | - Tingcai Cheng
- State Key Laboratory of Resource Insects, Southwest University, Chongqing 400716, China.
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3
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Ma Y, Li Q, Tang Y, Zhang Z, Liu R, Luo Q, Wang Y, Hu J, Chen Y, Li Z, Zhao C, Ran Y, Mu Y, Li Y, Xu X, Gong Y, He Z, Ba Y, Guo K, Dong K, Li X, Tan W, Zhu Y, Xiang Z, Xu H. The architecture of silk-secreting organs during the final larval stage of silkworms revealed by single-nucleus and spatial transcriptomics. Cell Rep 2024; 43:114460. [PMID: 38996068 DOI: 10.1016/j.celrep.2024.114460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 04/26/2024] [Accepted: 06/22/2024] [Indexed: 07/14/2024] Open
Abstract
Natural silks are renewable proteins with impressive mechanical properties and biocompatibility that are useful in various fields. However, the cellular and spatial organization of silk-secreting organs remains unclear. Here, we combined single-nucleus and spatially resolved transcriptomics to systematically map the cellular and spatial composition of the silk glands (SGs) of mulberry silkworms late in larval development. This approach allowed us to profile SG cell types and cell state dynamics and identify regulatory networks and cell-cell communication related to efficient silk protein synthesis; key markers were validated via transgenic approaches. Notably, we demonstrated the indispensable role of the ecdysone receptor (ultraspiracle) in regulating endoreplication in SG cells. Our atlas presents the results of spatiotemporal analysis of silk-secreting organ architecture late in larval development; this atlas provides a valuable reference for elucidating the mechanism of efficient silk protein synthesis and developing sustainable products made from natural silk.
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Affiliation(s)
- Yan Ma
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Qingjun Li
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Yiyun Tang
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Zhiyong Zhang
- Beijing SeekGene BioSciences Co., Ltd., Beijing 102206, China
| | - Rongpeng Liu
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Qin Luo
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Yuting Wang
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Jie Hu
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Yuqin Chen
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Zhiwei Li
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Chen Zhao
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Yiting Ran
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Yuanyuan Mu
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Yinghao Li
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Xiaoqing Xu
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Yuyan Gong
- Beijing SeekGene BioSciences Co., Ltd., Beijing 102206, China
| | - Zihan He
- Beijing SeekGene BioSciences Co., Ltd., Beijing 102206, China
| | - Yongbing Ba
- Shanghai OE Biotech. Co., Ltd., Shanghai 201212, China
| | - Kaiqi Guo
- Shanghai OE Biotech. Co., Ltd., Shanghai 201212, China
| | - Keshu Dong
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Xiao Li
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Wei Tan
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Yumeng Zhu
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Zhonghuai Xiang
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Hanfu Xu
- State Key Laboratory of Resource Insects, College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China.
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Zhang X, Yang L, Gan Q, Jiang S, Liang D, Gao J, Meng Y. BmTBP upregulates the transcription of BmSuc1 in silkworm (Bombyx mori) by binding to BmTfΙΙA-S. INSECT SCIENCE 2023; 30:1405-1419. [PMID: 36585848 DOI: 10.1111/1744-7917.13168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Revised: 12/06/2022] [Accepted: 12/11/2022] [Indexed: 06/17/2023]
Abstract
The BmSuc1 gene, which encodes a novel animal-type β-fructofuranosidase (EC 3.2.1.26), was first cloned and identified in silkworm (Bombyx mori). As an essential sucrase, the activity of BmSUC1 is unaffected by alkaloidal sugar mimics in mulberry leaves. This enzyme may also directly regulate the degree of sucrose hydrolysis in the silkworm midgut. In addition, BmSUC1 is involved in the synthesis of sericin 1 in the silk gland tissue. However, the mechanism underlying the regulation of BmSuc1 transcription remains unclear. In this study, we analyzed the BmSuc1 promoter activity using a dual-luciferase reporter assay and identified 4 regions that are critical for transcriptional activation. The gene encoding a predicted transcription factor (TATA-box-binding protein; BmTBP) capable of binding to the core promoter regions was cloned. A quantitative real-time polymerase chain reaction analysis indicated the gene was highly expressed in the midgut. Downregulating BmTBP expression via RNA interference decreased the expression of BmSuc1 at the transcript and protein levels. An electrophoretic mobility shift analysis and chromatin immunoprecipitation indicated that BmTBP can bind to the TATA-box cis-regulatory element in the BmSuc1 promoter. Furthermore, a bioinformatics-based analysis and a far-western blot revealed the interaction between BmTBP and another transcription factor (BmTfIIA-S). The luciferase reporter gene assay results confirmed that the BmTBP-BmTfIIA-S complex increases the BmSuc1 promoter activity. Considered together, these findings suggest that BmTBP regulates BmSuc1 expression through its interaction with BmTfIIA-S.
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Affiliation(s)
- Xinwei Zhang
- School of Life Sciences, Anhui Agricultural University, Hefei, China
- Department of Pathology, Henan Provincial People's Hospital, Zhengzhou, China
| | - Liangli Yang
- School of Life Sciences, Anhui Agricultural University, Hefei, China
- Anhui International Joint Research and Development Center of Sericulture Resources Utilization, Hefei, China
| | - Quan Gan
- Anhui Academy of Agricultural Sciences, Hefei, China
| | - Song Jiang
- School of Life Sciences, Anhui Agricultural University, Hefei, China
- Anhui International Joint Research and Development Center of Sericulture Resources Utilization, Hefei, China
| | - Dan Liang
- School of Life Sciences, Anhui Agricultural University, Hefei, China
- Anhui International Joint Research and Development Center of Sericulture Resources Utilization, Hefei, China
| | - Junshan Gao
- School of Life Sciences, Anhui Agricultural University, Hefei, China
| | - Yan Meng
- School of Life Sciences, Anhui Agricultural University, Hefei, China
- Anhui International Joint Research and Development Center of Sericulture Resources Utilization, Hefei, China
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5
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Zhang Q, Hua X, Sun Y, Lin Z, Cao Y, Zhao P, Xia Q. Dynamic chromatin conformation and accessibility changes mediate the spatial-specific gene regulatory network in Bombyx mori. Int J Biol Macromol 2023; 240:124415. [PMID: 37060980 DOI: 10.1016/j.ijbiomac.2023.124415] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2023] [Revised: 04/06/2023] [Accepted: 04/07/2023] [Indexed: 04/17/2023]
Abstract
Silk gland genes of Bombyx mori can have strict spatial expression patterns, which impact their functions and silk quality; however, our understanding of their regulation mechanisms is currently insufficient. To address this, the middle silk gland (MSG) and posterior silk gland (PSG) of the silkworm were investigated. Gene ontology annotation showed that spatially specific expressed genes were involved in the formation of H3k9me and chromatin topology. Chromatin conformation data generated by Hi-C showed that the topologically associated domain boundaries around FibL and Sericin1 genes were significantly different between MSG and PSG. Changes in chromatin conformation led to changes in chromatin activity, which significantly affected the expression of nearby genes in silkworm. Chromatin accessibility regions of MSG and PSG were analyzed using FAIRE-seq, and 1006 transcription factor motifs were identified in open chromatin regions. Furthermore, the spatial-specific expression patterns of silk gland genes were mainly associated with homeobox-contained transcription factors, such as POU-M2, which was specifically bound and relatively highly expressed in the MSG. The regulatory network mediated by POU-M2 regulated most of the spatial-specific expressed genes in MSG, such as ADH1. These results can aid in improving silk performance, optimizing silkworm breeding, and improving the gene spatial regulatory model research for insects.
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Affiliation(s)
- Quan Zhang
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, 400715 Chongqing, China; Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, 400715 Chongqing, China; Engineering Laboratory of Sericultural and Functional Genome and Biotechnology, Development and Reform Commission, 400715 Chongqing, China
| | - Xiaoting Hua
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, 400715 Chongqing, China; Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, 400715 Chongqing, China; Engineering Laboratory of Sericultural and Functional Genome and Biotechnology, Development and Reform Commission, 400715 Chongqing, China
| | - Yueting Sun
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, 400715 Chongqing, China; Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, 400715 Chongqing, China
| | - Zhongying Lin
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, 400715 Chongqing, China
| | - Yang Cao
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, 400715 Chongqing, China; Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, 400715 Chongqing, China; Engineering Laboratory of Sericultural and Functional Genome and Biotechnology, Development and Reform Commission, 400715 Chongqing, China.
| | - Ping Zhao
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, 400715 Chongqing, China; Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, 400715 Chongqing, China; Engineering Laboratory of Sericultural and Functional Genome and Biotechnology, Development and Reform Commission, 400715 Chongqing, China.
| | - Qingyou Xia
- Biological Science Research Center, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Southwest University, 400715 Chongqing, China; Key Laboratory for Germplasm Creation in Upper Reaches of the Yangtze River, Ministry of Agriculture and Rural Affairs, 400715 Chongqing, China; Engineering Laboratory of Sericultural and Functional Genome and Biotechnology, Development and Reform Commission, 400715 Chongqing, China.
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6
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Lu W, Ma S, Sun L, Zhang T, Wang X, Feng M, Wang A, Shi R, Jia L, Xia Q. Combined CRISPR toolkits reveal the domestication landscape and function of the ultra-long and highly repetitive silk genes. Acta Biomater 2023; 158:190-202. [PMID: 36603730 DOI: 10.1016/j.actbio.2022.12.063] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 12/23/2022] [Accepted: 12/27/2022] [Indexed: 01/04/2023]
Abstract
Highly repetitive sequences play a major structural and function role in the genome. In the present study, we developed Cas9-assisted cloning and SMRT sequencing of long repetitive sequences (CACS) to sequence and manipulate highly repetitive genes from eukaryotic genomes. CACS combined Cas9-mediated cleavage of a target segment from an intact genome, Gibson assembly cloning, and PacBio SMRT sequencing. Applying CACS, we directly cloned and sequenced the complete sequences of fibroin heavy chain (FibH) genes from 17 domesticated (Bombyx mori) and 7 wild (Bombyx mandarina) silkworms. Our analysis revealed the unique fine structure organization, genetic variations, and domestication dynamics of FibH. We also demonstrated that the length of the repetitive regions determined the mechanical properties of silk fiber, which was further confirmed by Cas9 editing of FibH. CACS is a simple, robust, and efficient approach, providing affordable accessibility to highly repetitive regions of a genome. STATEMENT OF SIGNIFICANCE: Silkworm silk is the earliest and most widely used animal fiber, and its excellent performance mainly depends on the fibroin heavy chain (FibH) protein. The FibH gene is the main breakthrough in understanding the formation mechanism and improvement of silk fiber. In the study, we developed a CACS method for characterizing the fine structure and domestication landscape of 24 silkworm FibH genes. We used CRISPR/Cas9 to edit the repetitive sequence of FibH genes, revealing the relationship between FibH genes and mechanical properties of silkworm silk. Our study is helpful in modifying silk genes to manipulate other valuable highly repetitive sequences, and provides insight for silkworm breeding.
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Affiliation(s)
- Wei Lu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China
| | - Sanyuan Ma
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China.
| | - Le Sun
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China
| | - Tong Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China
| | - Xiaogang Wang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Chinese Medicine & Health Science, Chongqing Academy of Chinese Materia Medica, Chongqing 400065, China
| | - Min Feng
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; College of Sericulture, Textile and Biomass Sciences, Southwest University, Chongqing 400715, China
| | - Aoming Wang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China
| | - Run Shi
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China
| | - Ling Jia
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China
| | - Qingyou Xia
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China; Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericulture, Southwest University, Chongqing 400715, China.
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7
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Lu W, Zhang T, Zhang Q, Zhang N, Jia L, Ma S, Xia Q. FibH Gene Complete Sequences (FibHome) Revealed Silkworm Pedigree. INSECTS 2023; 14:244. [PMID: 36975929 PMCID: PMC10055898 DOI: 10.3390/insects14030244] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2023] [Revised: 02/23/2023] [Accepted: 02/24/2023] [Indexed: 06/18/2023]
Abstract
The highly repetitive and variable fibroin heavy chain (FibH) gene can be used as a silkworm identification; however, only a few complete FibH sequences are known. In this study, we extracted and examined 264 FibH gene complete sequences (FibHome) from a high-resolution silkworm pan-genome. The average FibH lengths of the wild silkworm, local, and improved strains were 19,698 bp, 16,427 bp, and 15,795 bp, respectively. All FibH sequences had a conserved 5' and 3' terminal non-repetitive (5' and 3' TNR, 99.74% and 99.99% identity, respectively) sequence and a variable repetitive core (RC). The RCs differed greatly, but they all shared the same motif. During domestication or breeding, the FibH gene mutated with hexanucleotide (GGTGCT) as the core unit. Numerous variations existed that were not unique to wild and domesticated silkworms. However, the transcriptional factor binding sites, such as fibroin modulator-binding protein, were highly conserved and had 100% identity in the FibH gene's intron and upstream sequences. The local and improved strains with the same FibH gene were divided into four families using this gene as a marker. Family I contained a maximum of 62 strains with the optional FibH (Opti-FibH, 15,960 bp) gene. This study provides new insights into FibH variations and silkworm breeding.
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Affiliation(s)
- Wei Lu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
- Biological Science Research Center, Southwest University, Chongqing 400715, China
- Integrative Science Center of Gerplasm Greation in Western China (CHONGQING) Science City & Southwest University, Chongqing 400715, China
| | - Tong Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
- Biological Science Research Center, Southwest University, Chongqing 400715, China
- Integrative Science Center of Gerplasm Greation in Western China (CHONGQING) Science City & Southwest University, Chongqing 400715, China
| | - Quan Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
- Biological Science Research Center, Southwest University, Chongqing 400715, China
- Integrative Science Center of Gerplasm Greation in Western China (CHONGQING) Science City & Southwest University, Chongqing 400715, China
| | - Na Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
- Biological Science Research Center, Southwest University, Chongqing 400715, China
- Integrative Science Center of Gerplasm Greation in Western China (CHONGQING) Science City & Southwest University, Chongqing 400715, China
| | - Ling Jia
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
- Biological Science Research Center, Southwest University, Chongqing 400715, China
- Integrative Science Center of Gerplasm Greation in Western China (CHONGQING) Science City & Southwest University, Chongqing 400715, China
| | - Sanyuan Ma
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
- Biological Science Research Center, Southwest University, Chongqing 400715, China
- Integrative Science Center of Gerplasm Greation in Western China (CHONGQING) Science City & Southwest University, Chongqing 400715, China
| | - Qingyou Xia
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing 400715, China
- Biological Science Research Center, Southwest University, Chongqing 400715, China
- Integrative Science Center of Gerplasm Greation in Western China (CHONGQING) Science City & Southwest University, Chongqing 400715, China
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8
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Cao J, Zheng HS, Zhang R, Xu YP, Pan H, Li S, Liu C, Cheng TC. Dimmed gene knockout shortens larval growth and reduces silk yield in the silkworm, Bombyx mori. INSECT MOLECULAR BIOLOGY 2023; 32:26-35. [PMID: 36082617 DOI: 10.1111/imb.12810] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 08/30/2022] [Indexed: 06/15/2023]
Abstract
The bHLH domain transcription factor, Bombyx mori-derived dimmed (Bmdimm), is directly regulated by the JH-BmMet/BmSRC-BmKr-h1 pathway and plays a key role in regulating the expression of FibH, which codes the main component of silk protein. However, the other roles of Bmdimm in silk protein synthesis remain unclear. Here, we established a Bmdimm knockout (KO) line containing a 7-bp deletion via CRISPR/Cas9 system, which led to the absence of the bHLH domain. The expression level of silk protein genes and silk yield decreased significantly in the Bmdimm KO line. Moreover, knocking out Bmdimm led to shortened larval stages and significant weight loss in larvae and adults. Bmdimm was found to be highly expressed in the silk gland, but it was also expressed in the fat body. The expression level of Bmkr-h1 in the fat body was significantly downregulated in the Bmdimm KO line. Exogenous JHA treatment upregulated Bmkr-h1 and rescued the phenotype of larval growth in the Bmdimm KO line. In conclusion, knocking out Bmdimm led to a shortened larval stage via the inhibition of Bmkr-h1 expression, then reduced silk yield. These findings help to elucidate the regulatory mechanism of fibroin synthesis and larval development in silkworms.
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Affiliation(s)
- Jun Cao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Hong-Sheng Zheng
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Ran Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Yong-Ping Xu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Huan Pan
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Shan Li
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - Chun Liu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Cancer Center, Medical Research Institute, Southwest University, Chongqing, China
| | - Ting-Cai Cheng
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Cancer Center, Medical Research Institute, Southwest University, Chongqing, China
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Masuoka Y, Cao W, Jouraku A, Sakai H, Sezutsu H, Yokoi K. Co-Expression Network and Time-Course Expression Analyses to Identify Silk Protein Regulatory Factors in Bombyx mori. INSECTS 2022; 13:insects13020131. [PMID: 35206705 PMCID: PMC8924882 DOI: 10.3390/insects13020131] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/24/2021] [Revised: 01/25/2022] [Accepted: 01/25/2022] [Indexed: 02/04/2023]
Abstract
Simple Summary Previous studies have reported how the silk production ability of Bombyx mori can be enhanced, but the mechanism that regulates silk protein genes remains unclear. We performed co-expression network analysis using networkz, an in-house program, which led to the identification of 91 transcription factors were co-expressed with silk protein genes. Of them, 13 transcripts were identified to be novel regulatory factors by time-course expression analysis during the fifth instar larvae stage. Their expression patterns were highly relevant to those of silk protein genes. Our results suggest that the two-step expression screening was robust and highly sensitive to screen relative genes, and a complex mechanism regulates silk protein production in B. mori. The novel candidates that were identified herein can serve as key genes to develop methods to enhance the silk protein production ability of B. mori. Abstract Bombyx mori is an important economic insect and an animal model in pharmacomedical research. Although its physiology has been studied for many years, the mechanism via which silk protein genes are regulated remains unclear. In this study, we performed two-step expression screening, namely co-expression network and time-course expression analyses to screen silk protein regulation factors. A co-expression network analysis using RNA-seq data that were obtained from various tissues, including the silk glands of B. mori, was performed to identify novel silk protein regulatory factors. Overall, 91 transcription factors, including some known ones, were found to be co-expressed with silk protein genes. Furthermore, time-course expression analysis during the fifth instar larvae stage revealed that the expression pattern of 13 novel transcription factors was highly relevant to that of silk protein genes and their known regulatory factor genes. In particular, the expression peak of several transcription factors (TFs) was detected before the expression of silk protein genes peak. These results indicated that a larger number of genes than expected may be involved in silk protein regulation in B. mori. Functional analyses of function-unknown transcription factors should enhance our understanding of this system.
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Affiliation(s)
- Yudai Masuoka
- Insect Design Technology Module, Division of Insect Advanced Technology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 1-2 Owashi, Tsukuba 305-8634, Ibaraki, Japan;
- Research Center for Agricultural Information Technology (RCAIT), National Agriculture and Food Research Organization (NARO), 1-31-1 Kannondai, Tsukuba 305-0856, Ibaraki, Japan;
- Correspondence: (Y.M.); (K.Y.); Tel.: +81-29-838-6129 (Y.M. & K.Y.)
| | - Wei Cao
- Research Center for Agricultural Information Technology (RCAIT), National Agriculture and Food Research Organization (NARO), 1-31-1 Kannondai, Tsukuba 305-0856, Ibaraki, Japan;
| | - Akiya Jouraku
- Insect Design Technology Module, Division of Insect Advanced Technology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 1-2 Owashi, Tsukuba 305-8634, Ibaraki, Japan;
| | - Hiroki Sakai
- Silkworm Research Module, Division of Silk-Producing Insect Biotechnology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 1-2 Owashi, Tsukuba 305-8634, Ibaraki, Japan; (H.S.); (H.S.)
| | - Hideki Sezutsu
- Silkworm Research Module, Division of Silk-Producing Insect Biotechnology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 1-2 Owashi, Tsukuba 305-8634, Ibaraki, Japan; (H.S.); (H.S.)
| | - Kakeru Yokoi
- Insect Design Technology Module, Division of Insect Advanced Technology, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), 1-2 Owashi, Tsukuba 305-8634, Ibaraki, Japan;
- Research Center for Agricultural Information Technology (RCAIT), National Agriculture and Food Research Organization (NARO), 1-31-1 Kannondai, Tsukuba 305-0856, Ibaraki, Japan;
- Correspondence: (Y.M.); (K.Y.); Tel.: +81-29-838-6129 (Y.M. & K.Y.)
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Multilayer fibroin/chitosan oligosaccharide lactate and pullulan immunomodulatory patch for treatment of hernia and prevention of intraperitoneal adhesion. Carbohydr Polym 2021; 265:118066. [PMID: 33966830 DOI: 10.1016/j.carbpol.2021.118066] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Revised: 03/26/2021] [Accepted: 04/08/2021] [Indexed: 11/20/2022]
Abstract
This study aims to develop a novel intraperitoneal two- or three-layered patch with immunomodulatory property for treatment of hernia, regeneration of abdominal wall and prevention of intraperitoneal adhesions. Polypropylene (PP) mesh, middle layer, was intended to provide mechanical support whereas pullulan (PUL) hydrogel coating layer was designed to prevent intraperitoneal adhesions. Fibroin/chitosan oligosaccharide lactate (F/COS) layer electrospun on one side of pullulan was chosen for immunomodulation and abdominal wall regeneration. Physical and mechanical properties and regenerative capacity of intraperitoneal patches were determined. Immunomodulatory property of electrospun layer and whole patch was studied by determining nitric oxide amount produced by RAW 264.7 macrophages. 25 % (w/v) PUL hydrogel and F/COS with 90:10 (w/w) ratio yielded optimal results. Here, we report that fabricated intraperitoneal patches successfully prevented cell adhesion on one side and increased cell viability and proliferation on other side, along with immunomodulation, in vitro.
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Hou S, Sun Y, Wu Y, Cheng T, Liu C. Bmsage is involved in the determination of cell number in the silk gland of Bombyx mori. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2019; 113:103205. [PMID: 31421207 DOI: 10.1016/j.ibmb.2019.103205] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/10/2019] [Accepted: 07/15/2019] [Indexed: 06/10/2023]
Abstract
The number of cells in tissues is under strict genetic control, and research on the determination of cell number is of great importance to understand the growth and development of organs. Bmsage, a bHLH transcription factor, is involved in the development of the silk gland during the embryonic stage in Bombyx mori. However, the mechanism by which it influences silk gland development is unclear. In the present study, we determined via immunofluorescence staining during the embryonic stage of Bombyx mori that Bmsage is expressed in silk gland cells from the beginning of development of the silk gland until its complete formation. By comparing different silkworm strains, we found that Bmsage expression is positively correlated with the number of silk gland cells. Bmsage knockdown by RNAi resulted in shorter silk glands and lower cell numbers, especially in the posterior silk gland. The silk gland lumen also shriveled, and the silk protein content was significantly lower than that in the control. Further investigation revealed that all cyclins decreased after knock down of Bmsage, and cyclin B and cyclin 3 were significantly down-regulated. Bmsage may be involved in the regulation of the cyclin pathway to control silk gland development. Taken together, it can be concluded from our results that Bmsage is involved in the determination of cell number in silk glands. Our results help clarify the process of cell number determination in silk gland and identify a potential target for silkworm breeding.
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Affiliation(s)
- Sihan Hou
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Yan Sun
- Biotechnology College, Southwest University, Chongqing, 400716, China
| | - Yangchun Wu
- Jiangsu Key Laboratory of Sericultural Biology and Biotechnology, School of Biotechnology, Jiangsu University of Science and Technology, Zhenjiang, Jiangsu, 212018, China; The Key Laboratory of Silkworm and Mulberry Genetic Improvement, Ministry of Agriculture, Sericultural Research Institute, Chinese Academy of Agricultural Science, Zhenjiang, Jiangsu, 212018, China
| | - Tingcai Cheng
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China
| | - Chun Liu
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, China.
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Chen Y, Bai B, Yan H, Wen F, Qin D, Jander G, Xia Q, Wang G. Systemic disruption of the homeostasis of transfer RNA isopentenyltransferase causes growth and development abnormalities in Bombyx mori. INSECT MOLECULAR BIOLOGY 2019; 28:380-391. [PMID: 30548717 DOI: 10.1111/imb.12561] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Isopentenylation at A37 (i6 A37) of some transfer RNAs (tRNAs) plays a vital role in regulating the efficiency and fidelity of protein synthesis. However, whether insects, which are well known for their highly efficient protein synthesis machinery, employ this regulatory mechanism remains uninvestigated. In the current study, a candidate tRNA isopentenyltransferase (IPT) gene with three alternative splicing isoforms (BmIPT1-BmIPT3) was identified in Bombyx mori (silkworm). Only BmIPT1 could complement a yeast mutant lacking tRNA IPT. Phylogenetic analysis showed that silkworm tRNA IPT is conserved in the Lepidoptera. BmIPT was expressed in all B. mori tissues and organs that were investigated, but was expressed at a significantly higher level in silk glands of the fourth instar compared to the first day of the fifth instar. Interestingly, BmIPT was expressed at a significantly higher level in the domesticated silkworm, B. mori, than in wild Bombyx mandarina in multiple tissues and organs. Knock-down of BmIPT by RNA interference caused severe abnormalities in silk spinning and metamorphosis. Constitutive overexpression of BmIPT1 using a cytoplasmic actin 4 promoter in B. mori raised its messenger RNA level more than sixfold compared with nontransgenic insects and led to significant decreases in the body weight and cocoon shell ratio. Together, these results confirm the first functional tRNA IPT in insects and show that a suitable expression level of tRNA IPT is vital for silk spinning, normal growth, and metamorphosis. Thus, i6 A modification at position A37 in tRNA probably plays an important role in B. mori protein synthesis.
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Affiliation(s)
- Y Chen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - B Bai
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - H Yan
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - F Wen
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - D Qin
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
| | - G Jander
- Boyce Thompson Institute, Ithaca, NY, USA
| | - Q Xia
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing Engineering and Technology Research Center for Novel Silk Materials, Southwest University, Chongqing, China
| | - G Wang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing Engineering and Technology Research Center for Novel Silk Materials, Southwest University, Chongqing, China
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Guo Z, Qin J, Zhou X, Zhang Y. Insect Transcription Factors: A Landscape of Their Structures and Biological Functions in Drosophila and beyond. Int J Mol Sci 2018; 19:ijms19113691. [PMID: 30469390 PMCID: PMC6274879 DOI: 10.3390/ijms19113691] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Revised: 11/16/2018] [Accepted: 11/16/2018] [Indexed: 12/17/2022] Open
Abstract
Transcription factors (TFs) play essential roles in the transcriptional regulation of functional genes, and are involved in diverse physiological processes in living organisms. The fruit fly Drosophila melanogaster, a simple and easily manipulated organismal model, has been extensively applied to study the biological functions of TFs and their related transcriptional regulation mechanisms. It is noteworthy that with the development of genetic tools such as CRISPR/Cas9 and the next-generation genome sequencing techniques in recent years, identification and dissection the complex genetic regulatory networks of TFs have also made great progress in other insects beyond Drosophila. However, unfortunately, there is no comprehensive review that systematically summarizes the structures and biological functions of TFs in both model and non-model insects. Here, we spend extensive effort in collecting vast related studies, and attempt to provide an impartial overview of the progress of the structure and biological functions of current documented TFs in insects, as well as the classical and emerging research methods for studying their regulatory functions. Consequently, considering the importance of versatile TFs in orchestrating diverse insect physiological processes, this review will assist a growing number of entomologists to interrogate this understudied field, and to propel the progress of their contributions to pest control and even human health.
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Affiliation(s)
- Zhaojiang Guo
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
| | - Jianying Qin
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
- Longping Branch, Graduate School of Hunan University, Changsha 410125, China.
| | - Xiaomao Zhou
- Longping Branch, Graduate School of Hunan University, Changsha 410125, China.
| | - Youjun Zhang
- Department of Plant Protection, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing 100081, China.
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Zhang X, Chang H, Dong Z, Zhang Y, Zhao D, Ye L, Xia Q, Zhao P. Comparative Proteome Analysis Reveals that Cuticular Proteins Analogous to Peritrophin-Motif Proteins are Involved in the Regeneration of Chitin Layer in the Silk Gland of Bombyx mori at the Molting Stage. Proteomics 2018; 18:e1700389. [PMID: 29687606 DOI: 10.1002/pmic.201700389] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Revised: 01/20/2018] [Indexed: 11/07/2022]
Abstract
The silk gland of silkworm produces silk proteins during larval development. Many studies have long focused on the silk gland of the fifth instar larvae, but few have investigated this gland at other larval stages. In the present study, the silk gland proteomes of the fourth instar and fourth molt are analyzed using liquid chromatography-tandem mass spectrometry. In total, 2654 proteins are identified from the silk gland. A high abundance of ribosomal proteins and RR-motif chitin-binding proteins is identified during day 2 of the fourth instar (IV-2) larval developmental stage, and the expression of cuticular proteins analogous to peritrophin (CPAP)-motif chitin-binding proteins is higher during the fourth molt (IV-M). In all, nine enzymes are found to be involved in the chitin regeneration pathway in the silk gland. Among them, two chitinase and two chitin deacetylases are identified as CPAP-motif proteins. Furthermore, the expression of CPAP3-G, the most abundant CPAP-motif cuticular protein in the silk gland during the IV-M stage, is investigated using western blot and immunofluorescence analyses; CPAP3-G shows a reverse changing trend with chitin in the silk gland. The findings of this study suggest that CPAP-motif chitin-binding proteins are involved in the degradation of the chitin layer in the silk gland. The data have been deposited to the ProteomeXchange with identifier PXD008677.
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Affiliation(s)
- Xiaolu Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, P. R. China
| | - Huaipu Chang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, P. R. China
| | - Zhaoming Dong
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, P. R. China.,Chongqing Engineering and Technology Research Center for Novel Silk Materials, Chongqing, 400716, P. R. China
| | - Yan Zhang
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, P. R. China.,Chongqing Engineering and Technology Research Center for Novel Silk Materials, Chongqing, 400716, P. R. China.,College of Biotechnology, Southwest University, Chongqing, 400716, China
| | - Dongchao Zhao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, P. R. China
| | - Lin Ye
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, P. R. China
| | - Qingyou Xia
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, P. R. China.,Chongqing Engineering and Technology Research Center for Novel Silk Materials, Chongqing, 400716, P. R. China
| | - Ping Zhao
- State Key Laboratory of Silkworm Genome Biology, Southwest University, Chongqing, 400716, P. R. China.,Chongqing Engineering and Technology Research Center for Novel Silk Materials, Chongqing, 400716, P. R. China
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Nuclear hormone receptor BmFTZ-F1 is involved in regulating the fibroin heavy chain gene in the silkworm, Bombyx mori. Biochim Biophys Acta Gen Subj 2016; 1860:2529-2536. [PMID: 27475001 DOI: 10.1016/j.bbagen.2016.07.025] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 06/28/2016] [Accepted: 07/25/2016] [Indexed: 11/24/2022]
Abstract
BACKGROUND The synthesis of silk protein is controlled by hormones. The expression of the nuclear hormone Bmftz-f1 in the posterior silk gland (PSG) is induced by 20-hydroxyecdysone in vivo and in vitro. However, whether Bmftz-f1 regulates silk protein expression is unknown. METHODS In our study, western blotting and quantitative polymerase chain reactions were conducted to detect the expression of FTZ-F1 in the PSG. Electrophoretic mobility shift, chromatin immunoprecipitation, far-western blotting, bimolecular fluorescence complementation, and dual luciferase reporter assays were performed to investigate the effect of FTZ-F1 on the fibH promoter. RESULTS (1) The expression of the hormone receptor BmFTZ-F1 was opposite to that of fibH. It was highly expressed in the PSG during the fourth molting stage and the beginning of the fifth instar, and then its expression decreased gradually until it disappeared at the end of the fifth instar and the wandering stage. (2) We identified a FTZ-F1 response element 390bp upstream of the transcription initiation site of the fibH promoter. (3) BmFTZ-F1 interacted with the basic helix-loop-helix transcription factor Bmdimm. (4) BmFTZ-F1 down-regulated fibH promoter activity and counteracted the effect of Bmdimm on fibH expression. CONCLUSIONS Integrating these results, we conclude that BmFTZ-F1 regulates the transcription of fibH by binding to the FTZ-F1 response element in the fibH promoter and counteracts the effect of Bmdimm on fibH expression. GENERAL SIGNIFICANCE These findings provide new insights into the mechanism of regulation of the silk protein gene.
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