Albino (al) is a tetrahydrobiopterin (BH4)-deficient mutant of the silkworm Bombyx mori

Tsuguru Fujii, Hiroaki Abe, Munetaka Kawamoto, Susumu Katsuma, Yutaka Banno, Toru Shimada

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15 Citations (Scopus)

Abstract

Albino (al) is a lethal mutant of Bombyx mori that exhibits a colourless cuticle after the first ecdysis and dies without feeding on mulberry. Previous studies have indicated that sclerotisation was insufficient because of defective phenylalanine and tyrosine metabolism in albino larvae. However, the genetic mechanism underlying the albino phenotype has not been determined. Dopamine plays a central role in insect cuticle colouration and sclerotisation. The pathway for dopamine biosynthesis from phenylalanine involves phenylalanine hydroxylase (PAH; EC 1.14.16.1) and tyrosine hydroxylase (TH; EC 1.14.16.2). Tetrahydrobiopterin (BH4) is an essential cofactor of aromatic amino acid hydroxylases, including PAH and TH. Thus, BH4 is indispensable for cuticle colouration and sclerotisation. Here we report on identifying mutations in the gene that encodes for the Bombyx homolog of 6-pyruvoyl-tetrahydropterin synthase (PTS) which is involved in the biosynthesis of BH4, in 2 strains with different al alleles. In strain a60 (al), a transposable element was inserted in exon 2 of BmPTS. In strain a61 (al2), an 11-bp deletion was identified in the exon 2 region of BmPTS. After oral administration of BH4 to the al2 larvae, the survival rate was effectively increased and the larval integument was pigmented. These results indicated that BmPTS was responsible for the albino mutants of B.mori. We conclude that (i) a mutation in BmPTS leads to an insufficient supply of BH4 and results in defective dopamine biosynthesis and (ii) lack of dopamine results in cuticle colouration and sclerotisation failure. Lemon (lem) is a BH4-deficient mutant. It has been reported that de novo synthesis of zygotic BH4 was indispensable for viability of the embryo in eggs laid by lem (lem/leml) females. We found that lem/lem, al2/al2 larvae produced by lem (lem/lem) females were viable during the first instar stage, suggesting that al2/al2 embryo could synthesis BH4 by using maternally transmitted BmPTS.

Original languageEnglish
Pages (from-to)594-600
Number of pages7
JournalInsect Biochemistry and Molecular Biology
Volume43
Issue number7
DOIs
Publication statusPublished - Jul 1 2013

Fingerprint

Bombyx
lemons
Bombyx mori
silkworms
albino
Dopamine
Biosynthesis
Phenylalanine Hydroxylase
Larva
sclerotization
Morus
mutants
Polycyclic aromatic hydrocarbons
dopamine
phenylalanine 4-monooxygenase
Phenylalanine
tyrosine 3-monooxygenase
Exons
Embryonic Structures
Molting

All Science Journal Classification (ASJC) codes

  • Biochemistry
  • Molecular Biology
  • Insect Science

Cite this

Albino (al) is a tetrahydrobiopterin (BH4)-deficient mutant of the silkworm Bombyx mori. / Fujii, Tsuguru; Abe, Hiroaki; Kawamoto, Munetaka; Katsuma, Susumu; Banno, Yutaka; Shimada, Toru.

In: Insect Biochemistry and Molecular Biology, Vol. 43, No. 7, 01.07.2013, p. 594-600.

Research output: Contribution to journalArticle

Fujii, Tsuguru ; Abe, Hiroaki ; Kawamoto, Munetaka ; Katsuma, Susumu ; Banno, Yutaka ; Shimada, Toru. / Albino (al) is a tetrahydrobiopterin (BH4)-deficient mutant of the silkworm Bombyx mori. In: Insect Biochemistry and Molecular Biology. 2013 ; Vol. 43, No. 7. pp. 594-600.
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AU - Abe, Hiroaki

AU - Kawamoto, Munetaka

AU - Katsuma, Susumu

AU - Banno, Yutaka

AU - Shimada, Toru

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AB - Albino (al) is a lethal mutant of Bombyx mori that exhibits a colourless cuticle after the first ecdysis and dies without feeding on mulberry. Previous studies have indicated that sclerotisation was insufficient because of defective phenylalanine and tyrosine metabolism in albino larvae. However, the genetic mechanism underlying the albino phenotype has not been determined. Dopamine plays a central role in insect cuticle colouration and sclerotisation. The pathway for dopamine biosynthesis from phenylalanine involves phenylalanine hydroxylase (PAH; EC 1.14.16.1) and tyrosine hydroxylase (TH; EC 1.14.16.2). Tetrahydrobiopterin (BH4) is an essential cofactor of aromatic amino acid hydroxylases, including PAH and TH. Thus, BH4 is indispensable for cuticle colouration and sclerotisation. Here we report on identifying mutations in the gene that encodes for the Bombyx homolog of 6-pyruvoyl-tetrahydropterin synthase (PTS) which is involved in the biosynthesis of BH4, in 2 strains with different al alleles. In strain a60 (al), a transposable element was inserted in exon 2 of BmPTS. In strain a61 (al2), an 11-bp deletion was identified in the exon 2 region of BmPTS. After oral administration of BH4 to the al2 larvae, the survival rate was effectively increased and the larval integument was pigmented. These results indicated that BmPTS was responsible for the albino mutants of B.mori. We conclude that (i) a mutation in BmPTS leads to an insufficient supply of BH4 and results in defective dopamine biosynthesis and (ii) lack of dopamine results in cuticle colouration and sclerotisation failure. Lemon (lem) is a BH4-deficient mutant. It has been reported that de novo synthesis of zygotic BH4 was indispensable for viability of the embryo in eggs laid by lem (lem/leml) females. We found that lem/lem, al2/al2 larvae produced by lem (lem/lem) females were viable during the first instar stage, suggesting that al2/al2 embryo could synthesis BH4 by using maternally transmitted BmPTS.

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