Lepidopteran wing scales contain abundant cross-linked film-forming histidine-rich cuticular proteins

Jianqiu Liu,Li Peng,Yingdan Xiao,Judith H Willis,Qingyou Xia,Jiwei Zhang,Wanshun Li,Zhiwei Chen,K P Gopinathan ,Ping Zhao,Yan Zhang,Kallare P Arunkumar,Marian R Goldsmith,Shenglong Li,Ningjia He,Tsunaki Asano,Enxiang Chen,Xiaoling Tong,Keiko Kadono-Okuda,Kazuei Mita

doi:10.1038/s42003-021-01996-4

Abstract

Scales are symbolic characteristic of Lepidoptera; however, nothing is known about the contribution of cuticular proteins (CPs) to the complex patterning of lepidopteran scales. This is because scales are resistant to solubilization, thus hindering molecular studies. Here we succeeded in dissolving developing wing scales from Bombyx mori, allowing analysis of their protein composition. We identified a distinctive class of histidine rich (His-rich) CPs (6%–45%) from developing lepidopteran scales by LC-MS/MS. Functional studies using RNAi revealed CPs with different histidine content play distinct and critical roles in constructing the microstructure of the scale surface. Moreover, we successfully synthesized films in vitro by crosslinking a 45% His-rich CP (BmorCPR152) with laccase2 using N-acetyl- dopamine or N-β-alanyl-dopamine as the substrate. This molecular study of scales provides fundamental information about how such a fine microstructure is constructed and insights into the potential application of CPs as new biomaterials.

Highlights

Scales are symbolic characteristic of Lepidoptera; nothing is known about the contribution of cuticular proteins (CPs) to the complex patterning of lepidopteran scales
LC-MS/MS of the soluble scale proteins allowed us to identify the CPs and enzymes related to cuticular sclerotization, which revealed a possible mechanism of scale formation
The size and shape of scales in P-5 became similar to the mature ones; they remained soft and even dissolved partially in phosphate buffered saline (PBS)

Summary

Introduction

Scales are symbolic characteristic of Lepidoptera; nothing is known about the contribution of cuticular proteins (CPs) to the complex patterning of lepidopteran scales. We carried out liquid chromatograph-tandem mass spectrometry (LC-MS/MS) analysis of extracts from P-6 and P-8 wing scales which detected peptides (Supplementary Data 1–4) originating from 1257 and 1090 proteins. The detection of Arp2/3 (Gene009685) at P-6 (Supplementary Data 1–2) in our study suggested re-organization of F-actin may occur in B. mori scales.

Results

Conclusion