Spliceosomal Protein Gene BmSPX Regulates Reproductive Organ Development in Bombyx mori.

Yao Wang,Qin Zhao,Kai-Xuan Wang,Xing-Fu Zha,Qiu-Xing Wan,Juan Li

doi:10.3390/ijms21072579

Yao Wang, Qin Zhao + Show 4 more

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https://doi.org/10.3390/ijms21072579

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Abstract

Sex determination and differentiation are nearly universal to all eukaryotic organisms, encompassing diverse systems and mechanisms. Here, we identified a spliceosomal protein gene BmSPX involved in sex determination of the lepidopeteran insect, Bombyx mori. In a transgenic silkworm line that overexpressed the BmSPX gene, transgenic silkworm males exhibited differences in their external genitalia compared to wild-type males, but normal internal genitalia. Additionally, transgenic silkworm females exhibited a developmental disorder of the reproductive organs. Upregulation of BmSPX significantly increased the expression levels of sex-determining genes (BmMasc and BmIMP) and reduced the female-type splice isoform of Bmdsx, which is a key switch gene downstream of the sex-determination pathway. Additionally, co-immunoprecipitation assays confirmed an interaction between the BmSPX protein and BmPSI, an upstream regulatory factor of Bmdsx. Quantitative real-time PCR showed that BmSPX over-expression upregulated the expression of the Hox gene abdominal-B (Adb-B), which is required for specification of the posterior abdomen, external genitalia, and gonads of insects, as well as the genes in the Receptor Tyrosine Kinase (RTK) signaling pathway. In conclusion, our study suggested the involvement of BmSPX, identified as a novel regulatory factor, in the sex-determination pathway and regulation of reproductive organ development in silkworms.

Highlights

Sex determination is a fundamental process, in almost all eukaryotic organisms, that controls morphological, physiological, and behavioral differences between the sexes
To determine whether BmSPX participates in sex determination of the silkworm, the piggyback-BmSPX vector and helper vector were micro-injected into silkworm embryos (Figure 1A)
Sequence analysis showed that transgenic BmSPX was located in chromosome 11, and the insert site was located in the intergenic region (Table 1)

Summary

Introduction

Sex determination is a fundamental process, in almost all eukaryotic organisms, that controls morphological, physiological, and behavioral differences between the sexes. Females and males are determined by diverse mechanisms in many taxa, such as insects [1,2]. The bottom of sex determination systems in insects are conserved, and there are diverse primary signals at the top of the sex determination pathway [3]. The primary signal that triggers sex determination is processed by a cascade of genes, ending with the conserved switch gene doublesex (dsx) that controls sexual differentiation. In Drosophila, the process is controlled by the primary signal, the number of X chromosomes [4], and a regulatory cascade involving key genes such as Sex lethal, transformer (tra), and dsx [5]. The underlying mechanism of silkworm sex determination is clearly different from that of Drosophila

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