Responses of Mentha suspension-cultured cells to 2,4-dichlorophenoxyacetic acid and accumulation of esterified phenolic acids in their cell walls.

Two distinct types of cell growth of suspension-cultured Mentha were formed when the cells maintained in the medium containing 1000 micrograms l-1 2,4-D were subcultured into different 2,4-D concentrations. Few cell elongation of Mentha (average cell length: 34-40 microns) was observed after division in the medium containing 1-200 micrograms l-1 2,4-D; and significant cell elongation (average cell length: 95-130 microns) was observed after cell division in the medium containing 500-2000 micrograms l-1 2,4-D. A close correlation between culture medium and water content in the cells indicated that 2,4-D promoted cell elongation by water uptake. Amounts of phenolic acid in cell walls were much higher in unelongated cell walls than in elongated ones during the cultivation, and there was a close correlation between the amounts and the level of PAL activity in elongated and unelongated cells. However, there was no significant difference in cell wall components and its neutral sugar composition between elongated and unelongated cells.     

Subunit composition of RNA polymerase II from the fission yeast Schizosaccharomyces pombe

The subunit composition of RNA polymerase II (polII) was compared between the budding yeast Saccharomyces cerevisiae and the fission yeast Schizosaccharomyces pombe. For this purpose, we partially purified the enzyme from S. pombe. Judging from the co-elution profiles in column chromatographies of both the RNA polymerase activity and the two large subunit polypeptides (subunit 1 (prokaryotic β' homologue) and subunit 2 (β homologue)), the minimum number of S. pombe polII-associated polypeptides was estimated to be ten, less than the proposed subunit number of the S. cerevisiae enzyme. These ten putative subunits of S. pombe polII correspond to subunits 1, 2, 3, 5, 6, 7, 8, 10, 11 and 12 of the S. cerevisiae counterparts     

Genetic determinants of plasma triglyceride levels in (OLETF x BN) x OLETF backcross rats

Altered lipid metabolism is closely associated with diabetes in humans, although predisposing genetic factors that affect hyperlipidemia have not yet been clarified. Our previously established OLETF strain is an obese rat model of type II diabetes, exhibiting hypertriglycemia as well as hyperinsulinemia, hyperglycemia, insulin resistance, and abundant abdominal fat. To identify genetic factors responsible for dyslipidemic phenotypes in OLETF rats, we performed a whole-genome scan using 293 male (OLETF x BN) x OLETF backcross rats. Our analysis identified two significant quantitative trait loci (QTLs), on rat chromosomes 1 and 8, that are related to fasting triglyceride levels. The chromosome 1 QTL colocalized with Dmo1 (diabetes mellitus, OLETF type 1), a locus previously shown to associate strongly with both fat levels and body weight. The other significant QTL localizes to the chromosome 8 marker D8Mit2, in a region where several apo-lipoprotein genes are clustered.     

The novel gene HOMOLOGOUS PAIRING ABERRATION IN RICE MEIOSIS1 of rice encodes a putative coiled-coil protein required for homologous chromosome pairing in meiosis

We have identified and characterized a novel gene, PAIR1 (HOMOLOGOUS PAIRING ABERRATION IN RICE MEIOSIS1), required for homologous chromosome pairing and cytokinesis in male and female meiocytes of rice (Oryza sativa). The pair1 mutation, tagged by the endogenous retrotransposon Tos17, exhibited meiosis-specific defects and resulted in complete sterility in male and female gametes. The PAIR1 gene encodes a 492-amino acid protein, which contains putative coiled-coil motifs in the middle, two basic regions at both termini, and a potential nuclear localization signal at the C terminus. Expression of the PAIR1 gene was detected in the early stages of flower development, in which the majority of the sporocytes had not entered meiosis. During prophase I of the pair1 meiocyte, all the chromosomes became entangled to form a compact sphere adhered to a nucleolus, and homologous pairing failed. At anaphase I and telophase I, chromosome nondisjunction and degenerated spindle formation resulted in multiple uneven spore production. However, chromosomal fragmentation frequent in plant meiotic mutants was never observed in all of the pair1 meiocytes. These observations clarify that the PAIR1 protein plays an essential role in establishment of homologous chromosome pairing in rice meiosis.