Identification and Analysis of MicroRNAs Associated with Wing Polyphenism in the Brown Planthopper, Nilaparvata lugens.

Le Xu,Kang He,Mohamed A A Omar,Fei Li,Yaqin Wang,Wencai Jie,Jiao Zhang,Zhenghong Cao,Xingzhou Ma,Anran Zhan

doi:10.3390/ijms21249754

Abstract

Many insects are capable of developing two types of wings (i.e., wing polyphenism) to adapt to various environments. Though the roles of microRNAs (miRNAs) in regulating animal growth and development have been well studied, their potential roles in modulating wing polyphenism remain largely elusive. To identify wing polyphenism-related miRNAs, we isolated small RNAs from 1st to 5th instar nymphs of long-wing (LW) and short-wing (SW) strains of the brown planthopper (BPH), Nilaparvata lugens. Small RNA libraries were then constructed and sequenced, yielding 158 conserved and 96 novel miRNAs. Among these, 122 miRNAs were differentially expressed between the two BPH strains. Specifically, 47, 2, 27 and 41 miRNAs were more highly expressed in the 1st, 3rd, 4th and 5th instars, respectively, of the LW strain compared with the SW strain. In contrast, 47, 3, 29 and 25 miRNAs were more highly expressed in the 1st, 3rd, 4th and 5th instars, respectively, of the SW strain compared with the LW strain. Next, we predicted the targets of these miRNAs and carried out Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis. We found that a number of pathways might be involved in wing form determination, such as the insulin, MAPK, mTOR, FoxO and thyroid hormone signaling pathways and the thyroid hormone synthesis pathway. Thirty and 45 differentially expressed miRNAs targeted genes in the insulin signaling and insect hormone biosynthesis pathways, respectively, which are related to wing dimorphism. Among these miRNAs, Nlu-miR-14-3p, Nlu-miR-9a-5p and Nlu-miR-315-5p, were confirmed to interact with insulin receptors (NlInRs) in dual luciferase reporter assays. These discoveries are helpful for understanding the miRNA-mediated regulatory mechanism of wing polyphenism in BPHs and shed new light on how insects respond to environmental cues through developmental plasticity.

Highlights

Polyphenism, which occurs when organisms share the same genotype but exhibit two or more distinct phenotypes, is crucial for organisms to successfully deal with heterogeneous environments
To identify miRNAs associated with the development of wing morph plasticity, we first pooled 20 small RNA libraries constructed with RNA isolated from 1st to 5th instar nymphs of LW and SW brown planthopper (BPH) strains with two replicates per sample
The significance of miRNAs function in wing polymorphism will continue to grow as more genes and pathways identified to regulate the development of wing morphs

Summary

Introduction

Polyphenism, which occurs when organisms share the same genotype but exhibit two or more distinct phenotypes, is crucial for organisms to successfully deal with heterogeneous environments. This ecological phenomenon may be determined by multiple environmental conditions, including temperature, diet and population density [1]. Wing polyphenism is well known in insects, with distinct wing phenotypes conferring differential dispersal abilities [7,8,9]. Long-wing (LW) individuals with fully developed wings and flight muscles are capable of dispersing to new habitats, while short-wing (SW) or wingless individuals allocate resources to reproduction rather than to flight [1,10]

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Results

Conclusion