Search PubMed⌕ Search

Biomedical subjects

Rie Komori

Publications and source records attributed to Rie Komori.

5 recordsLinked to original sources
PubMed2005

A new mutation in the timing of autogamy in Paramecium tetraurelia.

We have isolated a new type of Paramecium tetraurelia mutant, named rie-2, that has a long immaturity period until autogamy. We previously isolated such an autogamy mutant, designated rie-1. These two mutants had some additional common features such as dependence of the occurrence of autogamy on the temperature, involvement of a single recessive gene, lower fission rate and shorter clonal life span. However, rie-2 was considered a new type mutant distinguishable from rie-1 because of their different natures of temperature sensitivity. First, the temperature at which they resembled the wild-type phenotype was low (19 degrees C) in rie-2, although it was high (32 degrees C) in rie-1. Second, the clonal life span of rie-2 at 25 degrees C was similar to that of the wild-type, but it was extremely shorter at 32 degrees C than at 25 degrees C, although it was similarly shorter at both temperatures in rie-1. Third, the difference of the fission rate between mutant and wild-type was greater at 32 degrees C than at 25 degrees C in rie-2, although it was similar at both temperatures in rie-1. This report shows that a gene mutation to elongate the period until sexual maturation does not necessarily assure the long life span.

Animals↗
PubMed2004

A Paramecium tetraurelia mutant that has long autogamy immaturity period and short clonal life span.

We have isolated an unprecedented mutant of Paramecium tetraurelia that has a long immaturity period until autogamy. This mutant stock, d4-RK, screened for 0% autogamy at the age of 27 fissions, began to undergo autogamy around the age of 50 fissions in some clones and underwent autogamy scarcely even after the age of 100 fissions in others. d4-RK expressed its mutant phenotype at 25 degrees C, but resembled the wild-type phenotype at 32 degrees C. Genetic analyses indicated that a single recessive gene, named rie (remote immaturity exit), was responsible for the mutant phenotype. This is the first report to show a gene that elongates the time to sexual maturation in unicellular organisms. The clonal life span was shorter and fission rate was lower in the rie mutant than in the wild-type, both at 25 degrees C and 32 degrees C. Even in the fourth autogamous generation following the third backcross to the wild-type, the progeny with the elongated autogamy immaturity period still had a short clonal life span and low fission rate, while those with the wild-type phenotype in autogamy immaturity period showed the wild-type phenotypes in clonal life span and fission rate, too.

Animals↗
PubMed2002

Variability of autogamy-maturation pattern in genetically identical populations of Paramecium tetraurelia.

Autogamy in Paramecium tetraurelia is a form of sexual reproduction in a single cell that results in homozygosity in every genetic locus. Autogamy becomes inducible by natural starvation several fissions after the previous autogamy, and percent autogamy increases gradually with clonal age to reach 100%. We here report the degree of variability of the autogamy-maturation pattern, and how it is inherited through autogamous generations. We assessed the autogamy-maturation pattern by monitoring percent autogamy at the ages of 9, 18 and 27 fissions in the wild-type stock 51. To determine how the autogamy-maturation pattern is inherited, clones that showed the lowest and the highest percent autogamy at age 18 in a given autogamous generation (Gn) were examined for their percent autogamy in the next autogamous generation (Gn+1). This procedure was repeated through successive autogamous generations. We found that percent autogamy at ages 9 and 27 was rather stable (low and high, respectively), while it was extremely variable at age 18 ranging from 3% to 100%. We also found that percent autogamy at age 18 in the progeny clones was variable irrespective of percent autogamy at age 18 in the parental clones; there was no regular rule such as producing progeny with higher (or lower) percent autogamy from parents with lower (or higher) percent autogamy.

Animals↗
PubMedDate not supplied

Abrupt increase in UV sensitivity at late log-phase of growth in Paramecium tetraurelia.

In this study, changes in UV sensitivity, a parameter of the clonal aging that has been studied in the daily reisolation culture, were examined in the logarithmically growing Paramecium culture. Cells in logarithmically growing cultures are thought to change the internal states under rapidly changing external conditions. In contrast, cells in daily reisolation cultures gradually change the internal states, the process being called clonal development and aging, under the external conditions that are kept almost constant. Cells were sampled at regular intervals, irradiated with UV, and examined for UV sensitivity assessed by the clonal survival. We found that log-phase cells showed low sensitivity to UV until they reached 2,000-3,000 cells/ml, and beyond that cell density, abruptly became highly UV sensitive. The extent of this increase in UV sensitivity was similar to that between two age groups, 130 fissions of clonal age apart. When cells from a culture of 2,000-3,000 cells/ml were resuspended in culture medium at various cell densities, they changed to UV sensitive only when the cultures reached over approximately 2,600 cells/ml. These results suggest that paramecia become UV sensitive in response to change in the nutrient level when cell density exceeds 2,000-3,000 cells/ml.

Animals↗