Comparative analysis of testis transcriptome between a genetic male sterile line (GMS) and its wild-type 898WB in silkworm, Bombyx mori

BmC/EBPZ gene is essential for the larval growth and development of silkworm, Bombyx mori

The genetic male sterile line (GMS) of the silkworm Bombyx mori is a recessive mutant that is naturally mutated from the wild-type 898WB strain. One of the major characteristics of the GMS mutant is its small larvae. Through positional cloning, candidate genes for the GMS mutant were located in a region approximately 800.5 kb long on the 24th linkage group of the silkworm. One of the genes was Bombyx mori CCAAT/enhancer-binding protein zeta (BmC/EBPZ), which is a member of the basic region-leucine zipper transcription factor family. Compared with the wild-type 898WB strain, the GMS mutant features a 9 bp insertion in the 3'end of open reading frame sequence of BmC/EBPZ gene. Moreover, the high expression level of the BmC/EBPZ gene in the testis suggests that the gene is involved in the regulation of reproduction-related genes. Using the CRISPR/Cas9-mediated knockout system, we found that the BmC/EBPZ knockout strains had the same phenotypes as the GMS mutant, that is, the larvae were small. However, the larvae of BmC/EBPZ knockout strains died during the development of the third instar. Therefore, the BmC/EBPZ gene was identified as the major gene responsible for GMS mutation.

Comparative multi-tissue analyses identify testis-specific serine/threonine protein kinase (TSSK) genes involved in male fertility in the melon fly Zeugodacus cucurbitae

BACKGROUND

Zeugodacus cucurbitae is an agricultural pest species with robust reproductive capabilities capable of causing extensive damage. The advent of novel male fertility-related pest control strategies has been an area of active entomological research focused on the sterile insect technique (SIT) strategy.

RESULTS

RNA-sequencing analyses were conducted using 16 tissue samples from adult male Z. cucurbitae, leading to the identification of 5338 genes that were differentially expressed between the testes and three other analyzed tissue types. Of these genes, 808 exhibited high levels of testis expression. A quantitative polymerase chain reaction (qPCR) approach was used to validate the expression of ten of these genes selected at random, including ZcTSSK1 and ZcTSSK3, which are testis-specific serine/threonine protein kinase (TSSK) genes. Evaluation via a loss-of-function-based knockdown assay showed that the down-regulation of either of these two genes in males was associated with significantly decreased egg hatching rates. In situ hybridization analyses revealed the expression of both of these transcripts in the transformation zone, and significant decreases in Z. cucurbitae sperm numbers were observed following double-stranded RNA treatment. Together, these results suggested that inhibiting ZcTSSK1 and ZcTSSK3 expression was sufficient to alter male fertility in Z. cucurbitae.

CONCLUSION

These transcriptional sequencing results provide a foundation for further efforts to clarify the regulators of Z. cucurbitae male fertility. These preliminary analyses of the functions of ZcTSSK family genes as regulators of spermatogenesis underscore their importance in the processes integral to male fecundity and their potential as targets for pest control efforts centered on the genetic manipulation of males. © 2023 Society of Chemical Industry.