BmHen1 is essential for eupyrene sperm development in Bombyx mori but PIWI proteins are not

Xu Yang; Dongbin Chen; Shirui Zheng; Meiyan Yi; Zulian Liu; Yongjian Liu; Dehong Yang; Yujia Liu; Linmeng Tang; Chenxu Zhu; Yongping Huang

doi:10.1016/j.ibmb.2022.103874

BmHen1 is essential for eupyrene sperm development in Bombyx mori but PIWI proteins are not

Insect Biochem Mol Biol. 2022 Dec:151:103874. doi: 10.1016/j.ibmb.2022.103874. Epub 2022 Nov 12.

Authors

Affiliations

¹ Key Laboratory of Insect Developmental and Evolutionary Biology, Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 200032, Shanghai, China; University of Chinese Academy of Sciences, 100049, Beijing, China.
² Key Laboratory of Insect Developmental and Evolutionary Biology, Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 200032, Shanghai, China.
³ Key Laboratory of Insect Developmental and Evolutionary Biology, Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 200032, Shanghai, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, 100049, China.
⁴ Key Laboratory of Insect Developmental and Evolutionary Biology, Center for Excellence in Molecular Plant Sciences, Shanghai Institute of Plant Physiology and Ecology, Chinese Academy of Sciences, 200032, Shanghai, China; CAS Center for Excellence in Biotic Interactions, University of Chinese Academy of Sciences, Beijing, 100049, China. Electronic address: yphuang@sibs.ac.cn.

PMID: 36375757
DOI: 10.1016/j.ibmb.2022.103874

Abstract

In lepidopteran insects, sperm dimorphism is a remarkable feature, in which males exhibit two different types of sperms. Both sperm morphs are essential for fertilization: Eupyrene sperm carry DNA and fertilize eggs, whereas apyrene sperm, which do not have nuclei, are necessary for transport of eupyrene sperm into eggs. In this study, we showed that the gene BmHen1, which encodes a methyltransferase that modifies piRNAs, is necessary for eupyrene sperm development in the lepidopteran model insect, Bombyx mori. Loss-of-function mutants of BmHen1 of both sexes were sterile. BmHen1 female mutants laid fewer eggs than wild-type females, and the eggs laid had morphological defects. Immunofluorescence analysis of BmHen1 male mutants revealed that nuclei formation in the eupyrene sperm was defective, whereas apyrene sperm were normal. In mice, worms, and flies, the components in piRNA biogenesis pathway play an important role in gonad development; therefore, we constructed mutations in genes encoding core elements in the piRNA biogenesis pathway, Siwi, and BmAgo3. To our surprise, no obvious phenotypes were observed in the male reproduction system in the Siwi and BmAgo3 mutants, which demonstrated that sperm development in B. mori does not depend on piRNAs. As the sperm development phenotype in BmHen1 mutants mimics the phenotype of the BmPnldc1 mutants, we then performed RNA sequencing analysis of sperm bundles from both mutants. We found that the defects in eupyrene sperm resulted from dysregulation of the expression of genes involved in energy metabolism. Taken together, our findings demonstrate the crucial functions of BmHen1 in the development of eupyrene sperm and provide evidence that spermatogenesis in B. mori is PIWI-independent. Our results suggest potential targets for lepidopteran pest control and broaden our knowledge of the reproduction in this order of insects.

Keywords: Bombyx mori; Dimorphic sperm; Hen1; PIWI proteins; piRNA biogenesis.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Animals
Bombyx* / genetics
Female
Male
Mice
RNA, Small Interfering / metabolism
Semen
Spermatogenesis / genetics
Spermatozoa / metabolism

Substances

RNA, Small Interfering