γΊ ΌΆCc i2001j
To determine the contribution of various compatible solutes to an increasein freezing tolerance in detail, accumulation of sugars, praline and glycine
betaine in leaves of three wheat cultivars was characterized and compared during cold acclimation. We have found that the concentration of sugars was much
greater than that of proline or glycine betaine after cold acclimation and accumulation of proline occurred earlier than that of glycine betaine during the
course of cold acclimation. There was a positive relationship between the extent of freezing tolerance and the sum of the concentration of sugars, proline
and glycine betaine after cold acclimation, while the contribution of these three compatible solutes to the increased osmolality in leaves seemed not to be
correlated with freezing tolerance during cold acclimation. Thus, these results suggest that the accumulation of compatible solutes has multiple roles in
increasing the freezing tolerance in plants.
K.-J. Wang, Y. Takahata, K. Ito, Y. Zhao, K. Tsutsumi and N. Kaizuma (2001)
Genetic characterization of a novel soybean kunitz trypsin inhibitor.
Breeding Sci. 51: 185-190.
Genetic and nucleotide sequence studies were performed on a new variant of soybean Kunitz trypsin inhibitor (SKTI) detected in wild soybean
(Glycine soja) and showing a slightly slower electrophoretic mobility than the Tia type. The segregation analysis of SKTI bands in F
2 seeds from crosses of the new variant type with Tia or Tib type showed that the variant type is controlled
by an allele codominant to Tia and Tib at an SKTI locus. Nucleotide sequence analysis showed that this variant has 217 amino acids composed
of 181 amino acid residues of mature SKTI and extra 25 and 11 amino acids at N- and C- terminal regions, respectively. This sequence was identical to that
of Tia (= KTi3), except that a G ¨ A transitional mutation occurred at position 500 of Tia, which results in the translational change
from Arg to Lys. The result of isoelectric focusing-PAGE coincided with this change. In addition, three nucleotides GCT were inserted at the N-terminus,
which leads to an Ala addition in the precursor of this SKTI protein. From these results, we propose the genetic symbol Tie for the new variant of
K. Otsu, K. Ito, T. Kuzumaki and Y. Iuchi (2001)
Differential regulation of liver-specific and ubiquitously expressed genesin primary rat hepatocytes by the extracellular matrix. Cell. Physiol.Biochem.
Primary rat hepatocytes were cultured with an extracellular matrix (ECM) overlay, in order to investigate the effect of an ECM on gene expression in
hepatocytes. When hepatocytes, isolated by the collagenase-perfusion method, were cultured on type I collagen-coated dishes, the mRNA levels of
liver-specific genes (aldolase B, tyrosine aminotransferase and albumin) decreased continuously, while those of ubiquitously-expressed genes
(glyceraldehyde 3-phosphate dehydrogenase gene andΐ-actin) increased.When a dilute ECM derived from the Engelbreth-Holm-Swarm mouse sarcoma (anEHS gel)
was added to the above hepatocytes 3 days after plating, the mRNA levels of liver-specific genes increased, while those of ubiquitously-expressed genes
decreased. The effects of a rat liver biomatrix (a physiological ECM for rat hepatocytes) on gene expression inprimary hepatocytes were similar to those
of the EHS gel. A nuclear run-on assay, and 5, 6-dichloro-1-ΐ-d-ribofuranosylbenzimidazole or actinomcin D treatments revealed that the transcriptional
rates of liver-specific genes were enhanced by the EHS gel overlay, while the apparent stability of the corresponding mRNAs were unchanged. In contrast,
the transcriptional rates of ubiquitously-expressed genes were not greatly affected by an EHS gel overlay, while the apparent stability of their mRNAs were
decreased. These data suggest that the ECM plays an important role in the maintenance of the differentiated characteristics of liver-specific genes and,
also, by destabilizing the mRNAs of ubiquitously-expressed genes.