![]() ![]() mori irrespective of the number of Z chromosomes. 3) In addition, Haruo Hasimoto reported that the W chromosome determines the femaleness of B. mori females are heterogametic (WZ), whereas B. As mentioned above, Yoshimaro Tanaka discovered that B. The WZ sex determination system is found in a diverse range of animals, such as birds, reptiles, and lepidopteran insects. DSX is a transcription factor that potentially binds to thousands of genome loci, leading to sex-specific gene expression and subsequent sexual differentiation. 8) dsx is sex-specifically spliced and translated into sex-specific DSX proteins. melanogaster and is called as doublesex ( dsx). However, in contrast to primary factors, the gene acting at the downstream end for sex differentiation is common between insects. 7) These discoveries revealed that the primary factors for insect sex determination cascades are also diverse. 3, 4) Recent progress in molecular biological techniques, such as deep sequencing by next-generation sequencers and genome editing methods, has enabled the identification of the primary genes involved the in sex determination cascades in various insects, including a small RNA, 5) a small protein (56 amino acid-long peptide), 6) and an RNA-binding protein. 2) In lepidopteran insects, the W chromosome is known to possess a strong feminizing factor in the silkworm Bombyx mori. 1) On the other hand, in hymenopteran insects, haploids and diploids become male and female, respectively. In dipterans, the signal for sex determination in Drosophila melanogaster is the number of X chromosomes, which reflects the dose of X-linked signaling elements. The mechanisms of sex determination in insects are surprisingly diverse. mori.ĭiversity and conservation in insect sex determination In this review, we summarize the history, current status, and perspective of studies on sex determination and related topics in B. These findings showed that the piRNA-mediated interaction between the two sex chromosomes is the primary signal for the sex determination cascade in B. Fem-derived piRNA binds to PIWI protein, and this complex then cleaves the mRNA of the Z-linked Masculinizer ( Masc) gene, which encodes a protein required for both masculinization and dosage compensation. In 2014, we discovered that Fem is a precursor of a single W chromosome-derived PIWI-interacting RNA (piRNA). Classical genetic studies revealed that a gene(s) with a strong feminizing activity is located on the W chromosome, but this W-linked feminizing gene, called Feminizer ( Fem), had not been cloned despite more than 80 years of study. mori has played an important role in the field of genetics. In addition to its contribution to sericulture, B. The silkworm Bombyx mori has been used for silk production for over 5,000 years. ![]()
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