1
|
Xiang Y, Tsuchiya D, Yu Z, Zhao X, McKinney S, Unruh J, Slaughter B, Lake CM, Hawley RS. Multiple reorganizations of the lateral elements of the synaptonemal complex facilitate homolog segregation in Bombyx mori oocytes. Curr Biol 2024; 34:352-360.e4. [PMID: 38176417 DOI: 10.1016/j.cub.2023.12.018] [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: 10/03/2023] [Revised: 11/29/2023] [Accepted: 12/07/2023] [Indexed: 01/06/2024]
Abstract
Although Lepidopteran females build a synaptonemal complex (SC) in pachytene, homologs do not crossover, necessitating an alternative method of homolog conjunction. In Bombyx mori oocytes, the SC breaks down at the end of pachytene, and homolog associations are maintained by a large oocyte-specific structure, which we call the bivalent bridge (BB), connecting paired homologs. The BB is derived from at least some components of the SC lateral elements (LEs). It contains the HORMAD protein HOP1 and the LE protein SYCP2 and is formed by the fusion of the two LE derivatives. As diplotene progresses, the BB increases in width and acquires a layered structure with a thick band of HOP1 separating two layers of SYCP2. The HOP1 interacting protein, PCH2, joins the BB in mid-diplotene, and by late-diplotene, it lies in the middle of the HOP1 filament. This structure is maintained through metaphase I. SYCP2 and PCH2 are lost at anaphase I, and the BB no longer connects the separating homologs. However, a key component of the BB, HOP1, remains at the metaphase I plate. These changes in organization of the BB occur simultaneously with the movement of the kinetochore protein, DSN1, from within the BB at mid-diplotene to the edge of the homologs facing the poles by metaphase I. We view these data in context of models in which SC components and regulators can be repurposed to achieve different functions, a fascinating example of evolution achieving homolog conjunction in an alternative way with recycling of SC proteins.
Collapse
Affiliation(s)
- Youbin Xiang
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Dai Tsuchiya
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Zulin Yu
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Xia Zhao
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Sean McKinney
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Jay Unruh
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Brian Slaughter
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - Cathleen M Lake
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA
| | - R Scott Hawley
- Stowers Institute for Medical Research, 1000 E. 50th Street, Kansas City, MO 64110, USA; Department of Molecular and Integrative Physiology, University of Kansas Medical Center, 3901 Rainbow Boulevard, Kansas City, MO 66160, USA.
| |
Collapse
|
2
|
Sakai H, Yokoyama T, Tomita S. Observing silkworm embryos at the fertilization stage using a tissue clearing reagent. JOURNAL OF INSECT PHYSIOLOGY 2022; 139:104386. [PMID: 35358539 DOI: 10.1016/j.jinsphys.2022.104386] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 03/02/2022] [Accepted: 03/25/2022] [Indexed: 06/14/2023]
Abstract
There are various reports on embryogenesis in silkworm, Bombyx mori, a model organism for lepidopteran insects. New tissue observation methods have been developed with the development of biological science. Applying these methods to silkworm eggs makes it possible to capture morphological and histological features that have not been observed until now. Tissue transparency technology is a method of observation that has advanced remarkably recently. This study emphasized the CUBIC (Clear, Unobstructed Brain/Body Imaging Cocktails and Computational analysis) method. The tissue clearing reagent used in CUBIC is water-soluble, containing urea and amino alcohol, which easily and effectively clears animal tissue by immersing the sample in the reagent. This study showed that silkworm eggs are made transparent using the modified CUBIC method at the fertilization stage. Furthermore, we observed the behavior of egg nucleus, polar body nuclei, and sperm nuclei at the fertilization stage.
Collapse
Affiliation(s)
- Hiroki Sakai
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan.
| | - Takeshi Yokoyama
- Department of United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan
| | - Shuichiro Tomita
- Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 1-2 Owashi, Tsukuba, Ibaraki 305-8634, Japan.
| |
Collapse
|
3
|
Kiuchi T, Katsuma S. Functional Characterization of Silkworm PIWI Proteins by Embryonic RNAi. METHODS IN MOLECULAR BIOLOGY (CLIFTON, N.J.) 2021; 2360:19-31. [PMID: 34495504 DOI: 10.1007/978-1-0716-1633-8_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 09/29/2022]
Abstract
The molecular mechanisms of sex-determination systems among insect orders and species are diverse. Therefore, genes involved in sex determination are strong candidates for insect pest management. Even though lepidopterans are major agricultural insect pests that cause widespread economic damage to various crops, their sex-determination systems have not been fully elucidated, even in the silkworm (Bombyx mori), a model lepidopteran insect. In 2014, we found that a female-specific W chromosome-derived PIWI-interacting RNA (piRNA) determines femaleness in silkworms. To analyze the function of two core silkworm piRNA biogenesis pathway genes, Siwi and BmAgo3, in the sex-determination system, we developed a genomic DNA and total RNA extraction strategy for a siRNA-injected single embryo. The siRNA-injected embryo can be molecularly sexed by W chromosome-specific DNA markers. Using complementary DNA (cDNA) reverse transcribed from the sexed RNA, we evaluated the knockdown effect of the PIWI protein-coding genes on a sexual development-related gene, Bombyx mori doublesex.
Collapse
Affiliation(s)
- Takashi Kiuchi
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
| | - Susumu Katsuma
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan
| |
Collapse
|
4
|
Sakai H, Sumitani M, Chikami Y, Yahata K, Uchino K, Kiuchi T, Katsuma S, Aoki F, Sezutsu H, Suzuki MG. Transgenic Expression of the piRNA-Resistant Masculinizer Gene Induces Female-Specific Lethality and Partial Female-to-Male Sex Reversal in the Silkworm, Bombyx mori. PLoS Genet 2016; 12:e1006203. [PMID: 27579676 PMCID: PMC5007099 DOI: 10.1371/journal.pgen.1006203] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 06/28/2016] [Indexed: 12/12/2022] Open
Abstract
In Bombyx mori (B. mori), Fem piRNA originates from the W chromosome and is responsible for femaleness. The Fem piRNA-PIWI complex targets and cleaves mRNAs transcribed from the Masc gene. Masc encodes a novel CCCH type zinc-finger protein and is required for male-specific splicing of B. mori doublesex (Bmdsx) transcripts. In the present study, several silkworm strains carrying a transgene, which encodes a Fem piRNA-resistant Masc mRNA (Masc-R), were generated. Forced expression of the Masc-R transgene caused female-specific lethality during the larval stages. One of the Masc-R strains weakly expressed Masc-R in various tissues. Females heterozygous for the transgene expressed male-specific isoform of the Bombyx homolog of insulin-like growth factor II mRNA-binding protein (ImpM) and Bmdsx. All examined females showed a lower inducibility of vitellogenin synthesis and exhibited abnormalities in the ovaries. Testis-like tissues were observed in abnormal ovaries and, notably, the tissues contained considerable numbers of sperm bundles. Homozygous expression of the transgene resulted in formation of the male-specific abdominal segment in adult females and caused partial male differentiation in female genitalia. These results strongly suggest that Masc is an important regulatory gene of maleness in B. mori.
Collapse
Affiliation(s)
- Hiroki Sakai
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Megumi Sumitani
- Transgenic Silkworm Research Unit, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Owashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Yasuhiko Chikami
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Kensuke Yahata
- Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
| | - Keiro Uchino
- Transgenic Silkworm Research Unit, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Owashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Takashi Kiuchi
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Susumu Katsuma
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Fugaku Aoki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
| | - Hideki Sezutsu
- Transgenic Silkworm Research Unit, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization (NARO), Owashi, Tsukuba, Ibaraki 305-8634, Japan
| | - Masataka G. Suzuki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba 277-8562, Japan
- * E-mail:
| |
Collapse
|
5
|
Sakai H, Kirino Y, Katsuma S, Aoki F, Suzuki MG. Morphological and histomorphological structures of testes and ovaries in early developmental stages of the silkworm, Bombyx mori. JOURNAL OF INSECT BIOTECHNOLOGY AND SERICOLOGY 2016; 85:15-20. [PMID: 28943775 DOI: 10.11416/jibs.85.1_015] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The gonad develops as a testis in male or an ovary in female. In the silkworm, B. mori, little is known about testis and ovary in the embryonic stages and early larval stages. In this study, we performed morphological and histomorphological observations of ovaries and testes from the late embryonic stage to the 1st instar larval stage. Results obtained with lack of accurate information on sex of examined individuals may be misleading, thus we performed phenotypic observations of gonads by utilizing sex-limited strain that enables us to easily discriminate female embryos from male ones based on those egg colors. In testis, four testicular follicles were clearly observed in the testis at the first instar larval stage, and boundary layers were formed between the testicular follicles. At the late embryonic stage, the testis consisted of four testicular follicles, while the boundary layers were still obscure. In ovary, four ovarioles were easily recognizable in the ovary at the first instar larval stage, and boundary layers were formed between the ovarioles. However, in the late embryonic stage, it was quite difficult to identify four ovarioles. Morphological characteristics were almost similar between testis and ovary in early developmental stages. Our present study demonstrates that the most reliable difference between testis and ovary in early developmental stages is the attaching point of the duct. Formation and development of the duct may be sensitive to the sex-determining signal and display sexual dimorphism in early embryonic stages.
Collapse
Affiliation(s)
- Hiroki Sakai
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan
| | - Yohei Kirino
- Computational Medicine Center, Sidney Kimmel Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
| | - Susumu Katsuma
- Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan
| | - Fugaku Aoki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan
| | - Masataka G Suzuki
- Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8562, Japan
| |
Collapse
|
6
|
Sakai H, Sakaguchi H, Aoki F, Suzuki MG. Functional analysis of sex-determination genes by gene silencing with LNA–DNA gapmers in the silkworm, Bombyx mori. Mech Dev 2015; 137:45-52. [DOI: 10.1016/j.mod.2015.03.002] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2015] [Revised: 03/20/2015] [Accepted: 03/23/2015] [Indexed: 02/02/2023]
|
7
|
A single female-specific piRNA is the primary determiner of sex in the silkworm. Nature 2014; 509:633-6. [PMID: 24828047 DOI: 10.1038/nature13315] [Citation(s) in RCA: 320] [Impact Index Per Article: 32.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2013] [Accepted: 04/08/2014] [Indexed: 11/08/2022]
Abstract
The silkworm Bombyx mori uses a WZ sex determination system that is analogous to the one found in birds and some reptiles. In this system, males have two Z sex chromosomes, whereas females have Z and W sex chromosomes. The silkworm W chromosome has a dominant role in female determination, suggesting the existence of a dominant feminizing gene in this chromosome. However, the W chromosome is almost fully occupied by transposable element sequences, and no functional protein-coding gene has been identified so far. Female-enriched PIWI-interacting RNAs (piRNAs) are the only known transcripts that are produced from the sex-determining region of the W chromosome, but the function(s) of these piRNAs are unknown. Here we show that a W-chromosome-derived, female-specific piRNA is the feminizing factor of B. mori. This piRNA is produced from a piRNA precursor which we named Fem. Fem sequences were arranged in tandem in the sex-determining region of the W chromosome. Inhibition of Fem-derived piRNA-mediated signalling in female embryos led to the production of the male-specific splice variants of B. mori doublesex (Bmdsx), a gene which acts at the downstream end of the sex differentiation cascade. A target gene of Fem-derived piRNA was identified on the Z chromosome of B. mori. This gene, which we named Masc, encoded a CCCH-type zinc finger protein. We show that the silencing of Masc messenger RNA by Fem piRNA is required for the production of female-specific isoforms of Bmdsx in female embryos, and that Masc protein controls both dosage compensation and masculinization in male embryos. Our study characterizes a single small RNA that is responsible for primary sex determination in the WZ sex determination system.
Collapse
|
8
|
Sakai H, Aoki F, Suzuki MG. Identification of the key stages for sex determination in the silkworm, Bombyx mori. Dev Genes Evol 2013; 224:119-23. [PMID: 24346480 PMCID: PMC3940855 DOI: 10.1007/s00427-013-0461-9] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2013] [Accepted: 12/02/2013] [Indexed: 11/25/2022]
Abstract
In general, the master switch gene for sex determination is expressed for a limited period during the early embryonic stage. To increase our understanding of the sex determination mechanism in Bombyx mori, it is important to understand when sex determination takes place. To examine the key stages for sex determination in this insect, we focused on the expression patterns of Bmdsx (a double-switch gene in the sex determination cascade of B. mori) and BmIMP (a gene expressed specifically in males involved in male-specific splicing of Bmdsx). Reverse transcription PCR (RT-PCR) analysis revealed that male-type Bmdsx expression was observed in females at 27 and 29 h after oviposition (hao), and finally disappeared at 32 hao. Moreover, BmIMP mRNA was also expressed in these females, and its expression level was comparable to that of the male-type Bmdsx mRNA. These results demonstrated that female embryos before 32 hao can show male-type expression of Bmdsx and BmIMP, suggesting that sex determination occurs between 29 and 32 hao, which correspond to the developmental stages from the head lobe differentiation to spoon-shaped embryo stages. This also suggests that the master switch gene for sex determination of B. mori is expressed in females during this period and represses the male-specific mode of expression in sex-determining genes.
Collapse
Affiliation(s)
- Hiroki Sakai
- Division of Biological Sciences, Department of Integrated Biosciences, Graduate School of Frontier Sciences, The University of Tokyo, 302 Bioscience-Bldg, 5-1-5 Kashiwanoha, Kashiwa-shi, Chiba-ken, 277-8562, Japan
| | | | | |
Collapse
|