Molecular and genetic analyses of the B type surface protein gene from Paramecium tetraurelia.
The gene encoding the B type variable surface protein from Paramecium tetraurelia stock 51 has been cloned and sequenced. The 7,182 nucleotide open reading frame contains no introns and encodes a cysteine-rich protein that has a periodic structure including three nearly perfect tandem repeats in the central region. Interestingly, the B gene is located near a macronuclear telomere as was shown previously for two other paramecium surface protein genes. In this paper, we characterize four independent mutants with complete macronuclear deletions of the B gene. Previous analysis of different macronuclear deletion mutants of the A surface protein gene demonstrated two types of inheritance: typical Mendelian segregation (as illustrated by d12) and cytoplasmic inheritance (shown by d48). F1 analysis of four B- mutants crossed with wild-type cells reveals heterozygous F1 cell lines derived from both parental cytoplasms contain approximately the same copy number of the B gene, as expected for a recessive Mendelian mutation. Analysis of F2 progeny from three of these four B- mutant crosses indicates that one of the three exhibits a Mendelian 1:1 segregation ratio of B+ and B- cell lines. The other two show a preponderance of B+ cells, but this is not correlated with the parental cytoplasmic type. In addition to having a large number of B+ individuals, the d12.144, A-, B- mutant produced some F2 progeny that stably maintain less than normal macronuclear amounts of the A gene and/or the B gene.
Department of Biochemistry, Purdue University, West Lafayette, Indiana 47907.
J
J
Scott
C
C
Leeck
J
J
Forney
D000818:Animals; D000953:Antigens, Protozoan / Q000235:genetics; D001483:Base Sequence; D003001:Cloning, Molecular; D003433:Crosses, Genetic; D016054:DNA, Protozoan / Q000235:genetics; D017125:Genes, Protozoan; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D016805:Paramecium tetraurelia / Q000235:genetics* / Q000276:immunology; D015800:Protozoan Proteins / Q000235:genetics* / Q000276:immunology; D015183:Restriction Mapping; D017384:Sequence Deletion
D000953:Antigens, Protozoan; D016054:DNA, Protozoan; D008565:Membrane Proteins; D015800:Protozoan Proteins