A self-fertile mutant of Phalaris produces an S protein with reduced thioredoxin activity |
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Authors: | Xinmin Li Jan Nield David Hayman Peter Langridge |
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Institution: | Centre for Cereal Biotechnology, Waite Institute, University of Adelaide, Glen Osmond, SA 5064, Australia;Department of Genetics, University of Adelaide, Adelaide, SA 5005, Australia |
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Abstract: | Gametophytic self-incompatibility in the Phalaris coerulescens is controlled by two unlinked genes, S and Z . Isolation of the S gene from the pollen of this grass species indicated that the C terminus has significant hemology with thioredoxin H proteins. The protein from the C terminus, expressed in Escherichia coli , exhibits thioredoxin-like activity. This paper demonstrates that the C terminus of the S protein from an S complete mutant shows significant reduction in thioredoxin activity when compared with the wild-type form. Both pollen and stigma have lost self-incompatibility in this mutant. Close examination of the lesions, which were found only in the C terminus of the mutant gene suggests that the substitution of a serine by an arginine is responsible for the reduced enzymatic activity. The association between reduced activity and the loss of the self-incompatibility provides evidence for a role of thioredoxin activity in the self-incompatibility reaction of this species. |
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