Leavening Ability of the Isolate Saccharomyces cerevisiae MF10003 in Bakery Dough

Halophytes are unique land plants that are capable of thriving in a high-salt environment. They are attracting public attention due to their ability to synthesize bioactive substances such as UV protectants or antioxidizing agents. To achieve unaffected growth under high salinity, halophytes may take advantage of the activities of cell growth factors such as expansins. Expansins are well-known cell wall proteins that are responsible for cell enlargement. They loosen cell walls, thereby contributing to actual plant growth. This study aimed to identify positive roles of expansins in the growth of halophytes. Three expansin cDNA clones were isolated from seedlings of Suaeda japonica. Comparing the deduced amino acid sequences of the expansin genes of S. japonica with those of other plant species suggested that the cDNA clones isolated from S. japonica belong to the EXPA (α-expansin) gene family. A phylogenetic tree based on the deduced amino acid sequences revealed that the expansins of S. japonica share a close evolutionary relationship with those of strawberry (Fragaria ananassa) and jujube (Ziziphus jujuba), both of which are woody dicots. SjEXPAs did not show any remarkable change in the gene expression level in different NaCl concentrations, providing a clue to the unaffected seedling growth of S. japonica in a high-salt environment. In conclusion, the present study presents the first report of expansin genes from halophytes and suggests a putative role for these genes in plant growth under high salinity.

Isolation and Characterization of Expansin Genes in a Halophyte, Suaeda japonica

Hwang¹,

Kim²,

Na³

et al. 2013

Gene Promoter Variation of Phosphoglycerate Kinase, a Glucose Metabolism Enzyme, is a Biomarker for Selection of Disease-resistant Sea Squirt, Halocynthia Roretzi

Cho¹,

Hur²,

Cheong

2013

The sea squirt, Halocynthia roretzi, has experienced mass mortality due to softness syndrome. The identification of disease-induced genes can provide insights into the development of this syndrome. To identify the genes, we performed differentially expressed gene (DEG) analysis. The expression of the phosphoglycerate kinase (HrPGK) gene was significantly decreased in diseased sea squirts compared to normal ones. We confirmed the result of the DEG analysis through RT-PCR and real-time PCR. In addition, we detected single nucleotide polymorphisms at position -106 (A/T) and -254 (G/T) in the HrPGK gene promoter by genotyping analysis. At the -106 site of the HrPGK gene, the frequency of the AA allele in disease-resistant sea squirts was about two-fold higher than that of sensitive ones, and the frequency of the TT allele in the disease-resistant sea squirts was about six-fold lower. At the -254 site of the HrPGK gene, the frequency of the GT and the GG allele was approximately two-fold higher and two-fold lower, respectively, in the disease-resistant sea squirts compared to the disease-sensitive ones. Analysis of the relationship between the genotypic variation at the -106/-254 promoter and the expression of HrPGK mRNA showed that HrPGK mRNA expression was higher in the -106/-254 AA/GT genotype samples than in the -106/254 TT/GG genotype ones. These results show that sea squirts harboring the AA/GT genotype may have more resistance to mortality than the sea squirts with other genotypes.

Presence of Leukemia-maintaining Cells in Differentiation-resistant Fraction of K562 Chronic Myelogenous Leukemia

Lee¹,

Kim²,

Ha³

et al. 2013

The present study investigated whether leukemia-maintaining cells reside in a differentiation-resistant fraction using a megakaryocytic differentiation model of K562 cells. Treatment with phorbol-12-myristate-13-acetate (PMA) significantly inhibited the colony-forming efficiency of the K562 cells. At a PMA concentration of 1 nM or higher, colony was not formed, but approximately 40% of K562 cells still survived in soft agar. Approximately 70% of colony-forming cells that were isolated following the removal of PMA after exposure to the agent were differentiated after treatment with 10 nM PMA for 3 days. The differentiation rate of the colony-forming cells was gradually increased and reached about 90% 6 weeks after colony isolation, which was comparable to the level of a PMA-treated K562 control. Meanwhile, imatinib-resistant variants from the K562 cells, including K562/R1, K562/R2, and K562/R3 cells, did not show any colony-forming activity, and most imatinib-resistant variants were CD44 positive. After 4 months of culture in drug-free medium, the surface level of CD44 was decreased in comparison with primary imatinib-resistant variants, and a few colonies were formed from K562/R3 cells. In these cells, Bcr-Abl, which was lost in the imatinib-resistant variants, was re-expressed, and the original phenotypes of the K562 cells were partially recovered. These results suggest that leukemia-maintaining cells might reside in a differentiation-resistant population. Differentiation therapy to eliminate leukemia-maintaining cells could be a successful treatment for leukemia if the leukemia-maintaining cells were exposed to a differentiation inducer for a long time and at a high dose.