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Ji X, Gao J, Wei T, Jin L, Xiao G. Fear-of-intimacy-mediated zinc transport is required for Drosophila fat body endoreplication. BMC Biol 2023; 21:88. [PMID: 37069617 PMCID: PMC10111752 DOI: 10.1186/s12915-023-01588-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Accepted: 04/03/2023] [Indexed: 04/19/2023] Open
Abstract
BACKGROUND Endoreplication is involved in the development and function of many organs, the pathologic process of several diseases. However, the metabolic underpinnings and regulation of endoreplication have yet to be well clarified. RESULTS Here, we showed that a zinc transporter fear-of-intimacy (foi) is necessary for Drosophila fat body endoreplication. foi knockdown in the fat body led to fat body cell nuclei failure to attain standard size, decreased fat body size and pupal lethality. These phenotypes could be modulated by either altered expression of genes involved in zinc metabolism or intervention of dietary zinc levels. Further studies indicated that the intracellular depletion of zinc caused by foi knockdown results in oxidative stress, which activates the ROS-JNK signaling pathway, and then inhibits the expression of Myc, which is required for tissue endoreplication and larval growth in Drosophila. CONCLUSIONS Our results indicated that FOI is critical in coordinating fat body endoreplication and larval growth in Drosophila. Our study provides a novel insight into the relationship between zinc and endoreplication in insects and may provide a reference for relevant mammalian studies.
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Affiliation(s)
- Xiaowen Ji
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, 230009, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China
| | - Jiajia Gao
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, 230009, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China
| | - Tian Wei
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, 230009, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China
- Department of Toxicology, School of Public Health, Anhui Medical University, Hefei, 230032, China
| | - Li Jin
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, 230009, China
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China
| | - Guiran Xiao
- China Light Industry Key Laboratory of Meat Microbial Control and Utilization, Hefei University of Technology, Hefei, 230009, China.
- School of Food and Biological Engineering, Hefei University of Technology, Hefei, 230009, China.
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Qian W, Guo M, Peng J, Zhao T, Li Z, Yang Y, Li H, Zhang X, King-Jones K, Cheng D. Decapentaplegic retards lipolysis during metamorphosis in Bombyx mori and Drosophila melanogaster. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2023; 155:103928. [PMID: 36870515 DOI: 10.1016/j.ibmb.2023.103928] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 01/29/2023] [Accepted: 03/01/2023] [Indexed: 05/10/2023]
Abstract
Insect morphogen decapentaplegic (Dpp) functions as one of the key extracellular ligands of the Bone Morphogenetic Protein (BMP) signaling pathway. Previous studies in insects mainly focused on the roles of Dpp during embryonic development and the formation of adult wings. In this study, we demonstrate a new role for Dpp in retarding lipolysis during metamorphosis in both Bombyx mori and Drosophila melanogaster. CRISPR/Cas9-mediated mutation of Bombyx dpp causes pupal lethality, induces an excessive and premature breakdown of lipids in the fat body, and upregulates the expressions of several lipolytic enzyme genes, including brummer (bmm), lipase 3 (lip3), and hormone-sensitive lipase (hsl), and lipid storage droplet 1 (lsd1), a lipid droplets (LD)-associated protein gene. Further investigation in Drosophila reveals that salivary gland-specific knockdown of the dpp gene and fat body-specific knockdown of Mad involved in Dpp signaling phenocopy the effects of Bombyx dpp mutation on pupal development and lipolysis. Taken together, our data indicate that the Dpp-mediated BMP signaling in the fat body maintains lipid homeostasis by retarding lipolysis, which is necessary for pupa-adult transition during insect metamorphosis.
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Affiliation(s)
- Wenliang Qian
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Mengge Guo
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Jian Peng
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Tujing Zhao
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Zheng Li
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Yan Yang
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Hao Li
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Xing Zhang
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Kirst King-Jones
- Department of Biological Sciences, University of Alberta, G-504 Biological Sciences Bldg., Edmonton, Alberta, T6G 2E9, Canada.
| | - Daojun Cheng
- State Key Laboratory of Silkworm Genome Biology, Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City & Southwest University, Biological Science Research Center, Southwest University, Chongqing, 400715, China; Chongqing Key Laboratory of Sericultural Science, Biological Science Research Center, Southwest University, Chongqing, 400715, China.
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3
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Variability of polyteny of giant chromosomes in Drosophila melanogaster salivary glands. Genetica 2023; 151:75-86. [PMID: 36163579 DOI: 10.1007/s10709-022-00168-4] [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: 07/20/2022] [Accepted: 09/13/2022] [Indexed: 02/01/2023]
Abstract
Polyteny is an effective mechanism for accelerating growth and enhancing gene expression in eukaryotes. The purpose of investigation was to study the genetic variability of polyteny degree of giant chromosomes in the salivary glands of Drosophila melanogaster Meig. in relation to the differential fitness of different genotypes. 16 strains, lines and hybrids of fruit flies were studied. This study demonstrates the significant influence of hereditary factors on the level of polytenization of giant chromosomes in Drosophila. This is manifested in the differences between strains and lines, the effect of inbreeding, chromosome isogenization, hybridization, adaptively significant selection, sexual differences, and varying degrees of individual variability of a trait in different strains, lines, and hybrids. The genetic component in the variability of the degree of chromosome polyteny in Drosophila salivary glands was 45.3%, the effect of sex was 9.5%. It has been shown that genetic distances during inbreeding, outbreeding or hybridization, which largely determine the selective value of different genotypes, also affect polyteny patterns. Genetic, humoral, and epigenetic aspects of endocycle regulation, which may underlie the variations in the degree of chromosome polyteny, as well as the biological significance of the phenomenon of endopolyploidy, are discussed.
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Qian W, Li H, Zhang X, Tang Y, Yuan D, Huang Z, Cheng D. Fzr regulates silk gland growth by promoting endoreplication and protein synthesis in the silkworm. PLoS Genet 2023; 19:e1010602. [PMID: 36652497 PMCID: PMC9886304 DOI: 10.1371/journal.pgen.1010602] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 01/30/2023] [Accepted: 01/06/2023] [Indexed: 01/19/2023] Open
Abstract
Silkworm silk gland cells undergo endoreplicating cycle and rapid growth during the larval period, and synthesize massive silk proteins for silk production. In this study, we demonstrated that a binary transgenic CRISPR/Cas9 approach-mediated Fzr mutation in silkworm posterior silk gland (PSG) cells caused an arrest of silk gland growth and a decrease in silk production. Mechanistically, PSG-specific Fzr mutation blocked endoreplication progression by inducing an expression dysregulation of several cyclin proteins and DNA replication-related regulators. Moreover, based on label-free quantitative proteome analysis, we showed in PSG cells that Fzr mutation-induced decrease in the levels of cyclin proteins and silk proteins was likely due to an inhibition of the ribosome biogenesis pathway associated with mRNA translation, and/or an enhance of the ubiquitin-mediated protein degradation pathway. Rbin-1 inhibitor-mediated blocking of ribosomal biogenesis pathway decreased DNA replication in PSG cells and silk production. Altogether, our results reveal that Fzr positively regulates PSG growth and silk production in silkworm by promoting endoreplication and protein synthesis in PSG cells.
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Affiliation(s)
- Wenliang Qian
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing engineering and technology research center for novel silk materials, Southwest University, Chongqing, China
- * E-mail: (WQ); (DC)
| | - Hao Li
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing engineering and technology research center for novel silk materials, Southwest University, Chongqing, China
| | - Xing Zhang
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing engineering and technology research center for novel silk materials, Southwest University, Chongqing, China
| | - Yaohao Tang
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing engineering and technology research center for novel silk materials, Southwest University, Chongqing, China
| | - Dongqin Yuan
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing engineering and technology research center for novel silk materials, Southwest University, Chongqing, China
| | - Zhu Huang
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing engineering and technology research center for novel silk materials, Southwest University, Chongqing, China
| | - Daojun Cheng
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, China
- Chongqing Key Laboratory of Sericultural Science, Chongqing engineering and technology research center for novel silk materials, Southwest University, Chongqing, China
- * E-mail: (WQ); (DC)
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Li Z, Qian W, Song W, Zhao T, Yang Y, Wang W, Wei L, Zhao D, Li Y, Perrimon N, Xia Q, Cheng D. A salivary gland-secreted peptide regulates insect systemic growth. Cell Rep 2022; 38:110397. [PMID: 35196492 DOI: 10.1016/j.celrep.2022.110397] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 11/10/2021] [Accepted: 01/26/2022] [Indexed: 11/03/2022] Open
Abstract
Insect salivary glands have been previously shown to function in pupal attachment and food lubrication by secreting factors into the lumen via an exocrine way. Here, we find in Drosophila that a salivary gland-derived secreted factor (Sgsf) peptide regulates systemic growth via an endocrine way. Sgsf is specifically expressed in salivary glands and secreted into the hemolymph. Sgsf knockout or salivary gland-specific Sgsf knockdown decrease the size of both the body and organs, phenocopying the effects of genetic ablation of salivary glands, while salivary gland-specific Sgsf overexpression increases their size. Sgsf promotes systemic growth by modulating the secretion of the insulin-like peptide Dilp2 from the brain insulin-producing cells (IPCs) and affecting mechanistic target of rapamycin (mTOR) signaling in the fat body. Altogether, our study demonstrates that Sgsf mediates the roles of salivary glands in Drosophila systemic growth, establishing an endocrine function of salivary glands.
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Affiliation(s)
- Zheng Li
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China
| | - Wenliang Qian
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China
| | - Wei Song
- Medical Research Institute, Wuhan University, Wuhan 430071, China; Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Tujing Zhao
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China
| | - Yan Yang
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China
| | - Weina Wang
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China
| | - Ling Wei
- School of Life Sciences, Southwest University, Chongqing 400715, China
| | - Dongchao Zhao
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China
| | - Yaoyao Li
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China
| | - Norbert Perrimon
- Department of Genetics, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA; Howard Hughes Medical Institute, Boston, MA 02115, USA.
| | - Qingyou Xia
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China.
| | - Daojun Cheng
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing 400715, China; Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing 400715, China.
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Guo MP, Qian WL, He XC, Peng J, Wang P, Wang WN, Xia QY, Cheng DJ. Genome-wide identification of target genes for transcription factor BR-C in the silkworm, Bombyx mori. INSECT SCIENCE 2021; 28:1530-1540. [PMID: 33372405 DOI: 10.1111/1744-7917.12893] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 10/23/2020] [Accepted: 11/22/2020] [Indexed: 06/12/2023]
Abstract
Transcription factor Broad Complex (BR-C) is an ecdysone primary response gene in insects and participates in the regulation of insect growth and development. In this study, we performed a genome-wide identification of BR-C target genes in silkworm (Bombyx mori) using chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-seq). As a result, a total of 1006 BR-C ChIP peaks were identified, and 15% of peaks were located in the promoter regions of 133 protein-coding genes. Functional annotation revealed that these ChIP peak-associated genes, as potential BR-C targets, were enriched in pathways related to biosynthetic process, metabolic process, and development. Transcriptome analysis and quantitative real-time polymerase chain reaction (PCR) examination revealed that developmental changes in expression patterns of a portion of potential BR-C targets, including HR96 and GC-α1, were similar to those of BR-C. ChIP-PCR examination confirmed that BR-C could directly bind to the promoters of potential targets. Further, dual luciferase assays demonstrated that HR96 promoter activity was significantly upregulated following BR-C overexpression, and this upregulation was abolished when the binding motif in the promoter was truncated. This study will be helpful for deciphering the regulatory roles of BR-C during insect growth and development.
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Affiliation(s)
- Meng-Pei Guo
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Wen-Liang Qian
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Xue-Chuan He
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Jian Peng
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Peng Wang
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Wei-Na Wang
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, China
| | - Qing-You Xia
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, China
- Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing, 400715, China
| | - Dao-Jun Cheng
- State Key Laboratory of Silkworm Genome Biology, Biological Science Research Center, Southwest University, Chongqing, 400715, China
- Chongqing Key Laboratory of Sericultural Science, Southwest University, Chongqing, 400715, China
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Histone H3K27 methylation-mediated repression of Hairy regulates insect developmental transition by modulating ecdysone biosynthesis. Proc Natl Acad Sci U S A 2021; 118:2101442118. [PMID: 34429358 DOI: 10.1073/pnas.2101442118] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Insect development is cooperatively orchestrated by the steroid hormone ecdysone and juvenile hormone (JH). The polycomb repressive complex 2 (PRC2)-mediated histone H3K27 trimethylation (H3K27me3) epigenetically silences gene transcription and is essential for a range of biological processes, but the functions of H3K27 methylation in insect hormone action are poorly understood. Here, we demonstrate that H3K27 methylation-mediated repression of Hairy transcription in the larval prothoracic gland (PG) is required for ecdysone biosynthesis in Bombyx and Drosophila H3K27me3 levels in the PG are dynamically increased during the last larval instar. H3K27me3 reduction induced by the down-regulation of PRC2 activity via inhibitor treatment in Bombyx or PG-specific knockdown of the PRC2 component Su(z)12 in Drosophila diminishes ecdysone biosynthesis and disturbs the larval-pupal transition. Mechanistically, H3K27 methylation targets the JH signal transducer Hairy to repress its transcription in the PG; PG-specific knockdown or overexpression of the Hairy gene disrupts ecdysone biosynthesis and developmental transition; and developmental defects caused by PG-specific Su(z)12 knockdown can be partially rescued by Hairy down-regulation. The application of JH mimic to the PG decreases both H3K27me3 levels and Su(z)12 expression. Altogether, our study reveals that PRC2-mediated H3K27 methylation at Hairy in the PG during the larval period is required for ecdysone biosynthesis and the larval-pupal transition and provides insights into epigenetic regulation of the crosstalk between JH and ecdysone during insect development.
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Enhanced Myc Expression in Silkworm Silk Gland Promotes DNA Replication and Silk Production. INSECTS 2021; 12:insects12040361. [PMID: 33919579 PMCID: PMC8073660 DOI: 10.3390/insects12040361] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Revised: 04/16/2021] [Accepted: 04/16/2021] [Indexed: 11/29/2022]
Abstract
Simple Summary Based on a transgenic approach, enhancing Myc expression in the silkworm posterior silk gland (PSG), which was driven by the promoter of the fibroin heavy chain (FibH) gene, was performed for investigating the biological functions of Myc in silk gland. Enhanced Myc expression elevated the cocoon size. This elevation might be resulted from the increasing of FibH expression and DNA content in the PSG cells by promoting the transcription of the genes that are involved in DNA replication. Abstract Silkworm is an economically important insect that synthetizes silk proteins for silk production in silk gland, and silk gland cells undergo endoreplication during larval period. Transcription factor Myc is essential for cell growth and proliferation. Although silkworm Myc gene has been identified previously, its biological functions in silkworm silk gland are still largely unknown. In this study, we examined whether enhanced Myc expression in silk gland could facilitate cell growth and silk production. Based on a transgenic approach, Myc was driven by the promoter of the fibroin heavy chain (FibH) gene to be successfully overexpressed in posterior silk gland. Enhanced Myc expression in the PSG elevated FibH expression by about 20% compared to the control, and also increased the weight and shell rate of the cocoon shell. Further investigation confirmed that Myc overexpression increased nucleus size and DNA content of the PSG cells by promoting the transcription of the genes involved in DNA replication. Therefore, we conclude that enhanced Myc expression promotes DNA replication and silk protein expression in endoreplicating silk gland cells, which subsequently raises silk yield.
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