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BmMBNL Knockout Disrupts Molting of Silkworm, Bombyx mori, Through Inhibiting Expressions of Chitin Synthetase and Chitinase
by
and
Huan Dong
,
Zihan Meng
,
Mengyao He
,
Yujuan Zhou
,
Ding Tu
,
He Wang
,
Xian Li
,
Yiwen Liang
,
Wenjuan Fan
,
Chaopin Zhu
,
Qingyou Xia
and
Feng Wang
*
Integrative Science Center of Germplasm Creation in Western China (CHONGQING) Science City, Biological Science Research Center, Southwest University, Chongqing 400715, China
*
Author to whom correspondence should be addressed.
Insects 2026, 17(8), 849; https://doi.org/10.3390/insects17080849
Submission received: 14 July 2026
/
Revised: 7 August 2026
/
Accepted: 12 August 2026
/
Published: 14 August 2026
(This article belongs to the Special Issue Recent Studies on Resource Insects)
Simple Summary
Insects rely on molting to replace their old cuticle for growth, a process tightly regulated at the molecular level. However, the role of miRNA processing in this event remains poorly understood. In this study, we investigated the function of Muscleblind-like (MBNL) protein in the silkworm Bombyx mori, which is involved in miRNA biogenesis. We found that BmMBNL is highly expressed in the epidermis and upregulated during molting. CRISPR/Cas9 knockout of BmMBNL caused severe molting defects, reduced body size, and larval lethality, accompanied by decreased ecdysone titers and impaired chitin layer formation. Mechanistically, loss of BmMBNL led to the upregulation of several miRNAs (miR-1, -71, -263, -8-5p, -2a-3p), which suppressed chitinase expression and disrupted normal molting. These findings reveal a novel miRNA-mediated regulatory axis that controls insect molting. Our work not only advances fundamental understanding of insect development but also provides potential targets for pest management and strategies to improve sericulture productivity, thus offering both ecological and economic benefits to society.
Abstract
Insects periodically undergo molting to replace their old epidermis for growth and morphological adaptation. Muscleblind-like (MBNL) is a multifunctional protein involved in miRNA processing. To explore the role of miRNA processing in insect molting, we characterized BmMBNL in Bombyx mori. BmMBNL exhibited spatiotemporal expression across tissues and developmental stages, with the highest levels in the epidermis and upregulation during molting. CRISPR/Cas9-mediated knockout of BmMBNL (BmMBNL-KO) caused molting defects at the 3rd and 4th instar larvae, resulting in reduced size and eventual lethality. Moreover, BmMBNL-KO individuals showed a thinner chitin layer between the new and old epidermises. RT-PCR and transcriptome analyses revealed upregulation of miR-1, miR-71, miR-263, miR-8-5p, and miR-2a-3p, which suppressed chitinase expression, ultimately leading to molting failure. This study provides novel insights into the potential correlation between BmMBNL, miRNA abundance and insect molting in Bombyx mori.
Keywords:
Bombyx mori; BmMBNL; CRISPR/Cas9; molting; chitinase; chitin synthase
