Yellow-e Determines the Color Pattern of Larval Head and Tail Spots of the Silkworm Bombyx mori

Katsuhiko Ito,Susumu Katsuma,Kimiko Yamamoto,Keiko Kadono-Okuda,Kazuei Mita,Toru Shimada

doi:10.1074/jbc.m109.035741

Katsuhiko Ito, Susumu Katsuma + Show 4 more

Open Access

https://doi.org/10.1074/jbc.m109.035741

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Abstract

Yellow proteins form a large family in insects. In Drosophila melanogaster, there are 14 yellow genes in the genome. Previous studies have shown that the yellow gene is necessary for normal pigmentation; however, the roles of other yellow genes in body coloration are not known. Here, we provide the first evidence that yellow-e is required for normal body color pattern in insect larvae. In two mutant strains, bts and its allele bts2, of the silkworm Bombyx mori, the larval head cuticle and anal plates are reddish brown instead of the white color found in the wild type. Positional cloning revealed that deletions in the Bombyx homolog of the Drosophila yellow-e gene (Bmyellow-e) were responsible for the bts/bts2 phenotype. Bmyellow-e mRNA was strongly expressed in the trachea, testis, and integument, and expression markedly increased at the molting stages. This profile is quite similar to that of Bmyellow, a regulator of neonatal body color and body markings in Bombyx. Quantitative reverse transcription-PCR analysis showed that Bmyellow-e mRNA was heavily expressed in the integument of the head and tail in which the bts phenotype is observed. The present results suggest that Yellow-e plays a crucial role in the pigmentation process of lepidopteran larvae.

Highlights

That the products of two other yellow genes, Dmyellow-f and Dmyellow-f2, have dopachrome-conversion enzyme activity [6]
In the bts body color mutant strain of B. mori, the larval head cuticle and anal plates are reddish brown instead of the white color found in the wild type (Fig. 1)
To examine spatial expression of Bmyellow-e in larval integument, we performed Quantitative RT-PCR (qRT-PCR) analysis using cDNA prepared from the integument of five compartments (Fig. 6A), and we found that it was heavily expressed in head and anal plates, where reddish coloration occurs in the bts strain (Fig. 6B)

Summary

Introduction

That the products of two other yellow genes, Dmyellow-f and Dmyellow-f2, have dopachrome-conversion enzyme activity [6]. Linkage analysis and genomic studies revealed that Bombyx yellow and ebony are the genes responsible for the ch and so mutation, respectively [9]. Primer sets for PCR of 12 bts candidate genes (Chinese gene to a position between 1,490,311 bp of Bm_scaf92 and the models BGIBMGA007217, 007218, 007219, 007220, 007221, 007222, 007236, 007237, 007238, 007253, 007308, and 007309) are listed in supplemental Table 1.

Results

Conclusion