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Divergence of a Tandem Duplication of Manganese Superoxide Dismutase in Nosema bombycis
Author(s) -
Wang Ying,
Zhang Ruizhi,
Barandun Jonas,
Du Huihui,
Chen Deming,
Jia Yuping,
Song Yue,
Vossbrinck Bettina,
Li Chong,
Zhou Zeyang,
Vossbrinck Charles R.,
Xiang Heng
Publication year - 2017
Publication title -
journal of eukaryotic microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.067
H-Index - 77
eISSN - 1550-7408
pISSN - 1066-5234
DOI - 10.1111/jeu.12442
Subject(s) - biology , superoxide dismutase , nosema , bombyx mori , microbiology and biotechnology , gene , biochemistry , enzyme , spore , microsporidia
Manganese superoxide dismutase (Mn SOD ) is a key enzyme in the protection of cells from oxidative stress. A tandem duplication of the Mn SOD gene ( NbMn SOD 1 and NbMn SOD 2 ) in the genome of Nosema bombycis, a parasite of the silkworm Bombyx mori , was previously identified. Here, we compare the protein structures of NbMn SOD 1 and NbMn SOD 2 and characterize these two proteins in terms of cellular localization, timing of transcription, protein structure, and enzyme activity. Despite a similarity in the primary sequence of NbMn SOD 1 and NbMn SOD 2 , the latter shows a remarkable degree of amino acid sequence difference on the protein's surface and in the active site, where there is a substitution of a phenylalanine for a histidine in NbMn SOD 2 . Immuno‐electron microscopy demonstrates that NbMn SOD 1 is present in the cytosol of mature spores, whereas NbMn SOD 2 is localized on the polar tube and the spore wall. Immunofluorescence confirms the localization of NbMn SOD 2 on the polar tube of the germinated spore. Quantitative measurement of gene expression ( qRT ‐ PCR ) demonstrates production of both alleles during the first day of infection followed by a dramatic decrease during the second to fourth day of infection. From the fifth day onward, the two alleles show a complementary pattern of expression. The qRT ‐ PCR of the host manganese superoxide dismutase ( BmMn SOD ) shows a notable increase in transcription upon infection, leading to a three‐fold spike by the first day of infection, followed by a decrease in transcription. Measurement of overall Mn SOD activity shows a similar peak at day 1 followed by a decrease to a constant rate of enzyme activity. The differences in cellular localization and pattern of gene expression of NbMn SOD 2 compared to NbMn SOD 1 , as well as the differences in protein structure seen for NbMn SOD 2 compared to other microsporidial Mn SOD s, strongly suggest a unique, recently evolved role for NbMn SOD 2 .