A self-fertile mutant of Phalaris produces an S protein with reduced thioredoxin activity.
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 homology with thioredoxin H proteins. The protein from the C terminus, expressed in Escherichia coli, exhibits thioredoxin-life 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-compatibility 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.
Li
X
X
Centre for Cereal Biotechnology, Waite Institute, University of Adelaide, Glen Osmond, Australia.
Nield
J
J
Hayman
D
D
Langridge
P
P
D000595:Amino Acid Sequence; D001483:Base Sequence; D004229:Dithiothreitol / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics*; D007328:Insulin / Q000378:metabolism; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010940:Plant Proteins; D006109:Poaceae / Q000235:genetics* / Q000502:physiology; D017354:Point Mutation / Q000235:genetics*; D011058:Pollen; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D012098:Reproduction; D013879:Thioredoxins / Q000235:genetics* / Q000378:metabolism*
D007328:Insulin; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C103488:S protein, Phalaris; D013879:Thioredoxins; D004229:Dithiothreitol