# A Maternal Gene Regulator CPEB2 Is Involved in Mating-Induced Egg Maturation in the Cnaphalocrocis medinalis

## TL;DR

This study shows that the CPEB2 gene is crucial for egg maturation in rice leaf roller moths, especially after mating and under the influence of juvenile hormone.

## Contribution

The study reveals CPEB2's role in insect reproduction, particularly its juvenile hormone-dependent regulation of egg maturation and oviposition in Cnaphalocrocis medinalis.

## Key findings

- CmCPEB2 is highly expressed in ovaries after mating and is regulated by the juvenile hormone pathway.
- Knockdown of CmCPEB2 leads to reduced vitellogenin deposition, ovarian defects, and lower fecundity.
- CmCPEB2 regulates genes involved in chorion formation and epithelial cell development.

## Abstract

Cytoplasmic polyadenylation element binding protein 2 (CPEB2) is a key protein in regulating oocyte maturation. However, its role in insect reproduction is not fully understood. In this study, a CPEB2 gene was identified in the rice leaf roller Cnaphalocrocis medinalis, an important agricultural pest insect. The analysis at both transcriptional and protein levels showed that CmCPEB2 was highly expressed in the ovaries after male–female mating and was upregulated by the juvenile hormone pathway. The potent knockdown of CmCPEB2 by liposome-facilitated RNA interference led to abnormal ovarian development and consequently reduced vitellogenin deposition and oviposition. Moreover, the expression levels of the genes associated with eggshells’ formation were significantly downregulated after the knockdown of CmCPEB2 as revealed by comparative transcriptomics analysis and moth-based assay. Overall, our study suggested that CmCPEB2 plays a crucial role in mating-induced egg maturation in C. medinalis.

Cytoplasmic polyadenylation element-binding proteins (CPEBs) are critical regulators of maternal mRNA translation during oogenesis, yet their roles in insect reproduction remain underexplored. Here, we characterized CmCPEB2, a CPEB homolog in the rice leaf roller Cnaphalocrocis medinalis, a destructive lepidopteran pest insect, and elucidated its role in mating-induced oviposition. The CmCPEB2 protein harbored conserved RNA recognition motifs and a ZZ-type zinc finger domain and was phylogenetically clustered with lepidopteran orthologs. Spatiotemporal expression profiling revealed CmCPEB2 was predominantly expressed in ovaries post-mating, peaking at 12 h with a 6.75-fold increase in transcript levels. Liposome-mediated RNA interference targeting CmCPEB2 resulted in a 52% reduction in transcript abundance, leading to significant defects in ovarian maturation, diminished vitellogenin deposition, and a 36.7% decline in fecundity. The transcriptomic analysis of RNAi-treated ovaries identified 512 differentially expressed genes, with downregulated genes enriched in chorion formation and epithelial cell development. Tissue culture-based hormonal assays demonstrated the juvenile hormone-dependent regulation of CmCPEB2, as JH treatment induced its transcription, while knockdown of the JH-responsive transcription factor CmKr-h1 in the moths suppressed CmCPEB2 expression post-mating. These findings established CmCPEB2 as a juvenile hormone-dependent regulator of mating-induced oviposition that orchestrates vitellogenesis through yolk protein synthesis and ovarian deposition and choriogenesis via transcriptional control of chorion-related genes. This study provides novel evidence of CPEB2-mediated reproductive regulation in Lepidoptera, highlighting its dual role in nutrient allocation and structural eggshell formation during insect oogenesis and oviposition.