Soon Young Kim

Effect of ethylene antagonists on auxin-induced inhibition of intact primary root elongation in maize (Zeamays L.)

Root elongation was measured in intact primary roots of maize(Zea mays L.) using a computerized root auxanometer. We examined the fact that root elongation was inhibited by auxin-induced ethylene production. Inhibition of root elongation was closely correlated with the concentrations of the exogenously applied auxin. Auxin-induced inhibition of root elongation was reversed by pretreatment or posttreatment of ethylene biosynthesis antagonists such as aminoethoxyvinylglycine (AVG) and silver ions (Ag2+). The magnitude of recovery effect was dependent on auxin concentrations. Root elongation was inhibited by adding ethylene producing agents such as 1-aminocyclopropane-l-carboxylic acid (ACC) and Ethephon. ACC- and Ethephon-induced inhibition of root elongation was reversed by blocking ethylene biosynthesis or activity. These data suggested that ethylene was involved in auxin-induced inhibition of root elongation and inhibition of root elongation by applied auxin, at least in part, was a reversible process.

Brassinosteroids affect ethylene production in the primary roots of maize (Zea mays L.)

To better understand the physiological roles of brassinosteroids (BRs) in the primary roots of maize, we examined their effect on ethylene production. Exogenously applied brassinolide (BL; 10-9 to 10-7 M) incrementally increased the level ethylene in a dose-dependent manner. This BL-induced production was enhanced in the presence of IAA, thereby implying a synergistic effect between BR and IAA. At 10-7 M BL, the level of free ACC was increased, but that of conjugated ACC was diminished. Moreover, greater concentrations of BL proportionally increased ACC oxidase activity. In contrast, higher levels of IAA increased the endogenous content of conjugated ACC as well as ACC synthase activity. Based on these results, we conclude that BR activates ethylene production mainly via ACC oxidase, and interacts with IAA to produce ethylene. However, the functional site for ethylene production is different for each hormone.

Anti-proliferative Activities of Solvent Fractions of Lees Extracts in Human Colorectal HCT116 Cells

In the present study, we prepared eighty-five different kinds of lees extracts and their solvent fractions and investigated their anti-proliferative activities against human colorectal cancer HCT116 cells. HCT116 cells were treated with eighty-five solvent fractions of lees extracts and then cell viability was measured using MTS assay. Among the treated solvent fractions, three solvent fractions (KSD-E1-3, KSD-E2-3, and KSD-E4-3) were selected based on cell viability assay. In addition, we performed an oligo DNA microarray analysis to analyze the gene expression changes by treatment of KSD-E1-3 in HCT116 cells. Among the up-regulated genes, we selected 4 genes (NAG-1, ATF3, p21, and DDIT3) and performed RT-PCR using gene-specific primers. Among the treated solvent fractions, KSD-E1-3 dramatically induced the expressions of the four selected genes. In addition, we investigated whether the up-regulations of those genes were dependent on the transcription factor p53’s presence using p53 null HCT116 cells. The results indicate that the up-regulations of NAG-1, ATF3, and DDIT3 are not dependent on the p53 presence, whereas p21 is dependent on the p53 presence. These findings may help to understand the molecular mechanisms of the anti-proliferative activity mediated by rice wine lees in human colorectal cancer cells.

Action of malformin A1 on gravitropic curvature in primary roots of maize (Zea mays L.)

Malformins, a small family of cyclic pentapeptides, are active plant growth regulators isolated from the fungusAspergillus niger. We purified malformin A1 from the crude malformin A mixture, and studied its action in the gravitropic response of maize roots. Intact primary roots that had been pretreated vertically with malformin A1 were placed in a humidified box in the horizontal position. Positive curvature (downward) was inhibited in the pretreated roots compared with the control. In addition, we measured the lateral transport of IAA in primary roots. Roots pretreated with malformin A, did not show asymmetric distribution of IAA between the upper and lower sides of the elongation zone. Malformin A, also stimulated ethylene production in maize root segments. Our results had suggested that malformin A1 might inhibit the lateral transport of IAA across the roots from the upper to the lower side because of an increased level of ethylene. Therefore, we placed more IAA on the upper side at the initial phase of gravistimulation. These results were consistent with malformin A1-pretreated roots showing inhibited positive gravitropic curvature.

Effect of auxin and ethylene on elongation of intact primary roots of maize (Zeamays L.)

We tested that the hypothesis that root elongation might be controlled by altering the level of ethylene in intact primary roots of maize(Zea mays L.). We measured root elongation in a short period using a computerized root auxanometer. Compounds which regulate ethylene production were applied to intact primary roots in different time periods. Root elongation was stimulated by the treatment with ethylene antagonists such as Co2+, aminoethoxyvinylglycine (AVG) and L-canaline. This result suggested that root elongation was closely related to ethylene level of intact primary roots. Furthermore, IAA- and 1-aminocyclopropane-1-carboxylic acid (ACC)-induced inhibition of root elongation was reversed by treatment with Co2+. The application of ACC to roots which have been exposed to IAA and Co2+ have no significant effect on root elongation. However, the inhibition of root elongation by ACC in roots previously treated with IAA and AVG became manifest when the applied IAA concentrations were lower. These results were consistent with the hypothesis that the level of ethylene in intact roots functions to moderate root elongation, and suggested that auxin-induced inhibition of root elongation results from auxin induced promotion of ethylene production.

Dose-dependent effects of malformin A1 on IAA-induced ethylene production in mung bean (Vigna radiate L.) hypocotyl segments

Purified malformin A1 (cyclo-D-Cys-D-Cys-L-Val-D-Leu-L-lle), a cyclicpentapeptide toxin fromAspergillus niger, was applied to the hypocotyl segments of mung bean (Vigna radiata L.) seedlings to investigate its role in regulating ethylene biosynthesis. Production of ethylene was induced by treating the plants with 0.1 mM indole-3-acetic acid (1AA). When 0.1 μM malformin A1 was then applied, ethylene production increased and the activities of two key enzymes for its biosynthesis, 1-aminocyclopropane-1-carboxylic acid (ACC)-synthase (ACS) and ACC-oxidase (ACO), were also stimulated. However, at levels of 1 or 10 μM malformin A1, both ethylene production and enzymatic activities were significantly reduced. In the case of ACO,in vitro activity was regulated by malformin A1, independent of ACS activity or the influence of IAA. Furthermore, the conjugate form of ACC, N-malonyl ACC, was significantly promoted by treatment with 0.1 μM malformin A1. These data suggest that malformin A1 can modulate ethylene production through diverse paths and that its effect depends on the concentration of the treatment administered.

Identification and bioavailability of a chromatin-binding peptide (Lunasin) from Korean Soybean

Lunasin is a novel peptide with great potential as a nontoxic chemopreventive drug. This compound might account for part of the anticancer effects reported from studies with soybean(Glycine max). We studied its isolation, purification and biological assay, and observed that both its band from soybean and one from synthetic lunasin were <5 kD in their molecular weights. Among all the crop varieties tested, only the soybean produced a lunasin band on our western blot. Levels of this peptide ranged from 0.045 mg per gram of seed for the Hanbatkong cultivar to 0.156 mg per gram seed for Poolunkong’. The effect on colony formation by lunasin from different soybean extracts was significantly higher than for either the positive control or the synthetic lunasin. When lunasin was present in those natural extracts, histone acetylation decreased 100% compared with cells that were treated with Na-butyrate.

Suppressive Effects of Lees from Sweet Potato Soju on LPS-induced Inflammatory Responses in RAW 264.7 Cells

In the current study, the ethanol extracts and their subsequent organic solvent fractions from lees of sweet potato soju were prepared and the prepared samples were designated as from KSD-E8-1 to KSD-E8-5. Their effects on cell viability and nitric oxide (NO) production in mouse macrophage RAW 264.7 cells were investigated. The results showed that the ethyl acetate fraction (KSD-E8-3) of lees ex-tracts from sweet potato soju significantly decreased nitric oxide (NO) production in LPS-activated RAW 264.7 cells, whereas they did not affect cell viabilities. The fraction KSD-E8-3 reduced the ex-pression of pro-inflammatory genes such as COX-2, iNOS and TNF-alpha and also decreased protein expression of iNOS in a dose dependent manner, which were detected with RT-PCR and Western blot analysis, respectively. In addition, we detected the expression of mitogen-activated protein kinases (MAPKs) such as p38, JNK, and ERK1/2 and their phosphorylated forms. The results indicated that the treatment of the fraction KSD-E8-3 did inhibit phosphorylation of p38, JNK, and ERK1/2 MAPKs, indicating that the fraction KSD-E8-3 regulates LPS-induced inflammatory response via suppressing MAPK signaling pathway. Overall, these results may contribute to understand the molecular mecha-nism of anti-inflammatory effects by the ethyl acetate fraction of lees extracts from sweet potato soju.

Up-Regulation of NAG-1 and p21 Genes by Sulforaphane

We investigated the anti-proliferative activity of sulforaphane and expression changes of NAG-1 and p21 genes in response to sulforaphane treatment in human colorectal HCT116 cells. The results showed that sulforaphane decreased cell viabilities in a dose-dependent manner and induced expression of NAG-1 and p21 proteins in a dose-dependent and time-dependent manner. In addition, we found that NAG-1 expression by sulforaphane was not dependent on the presence of p53, whereas p21 expression was dependent on p53 presence. The results indicated that up-regulation of NAG-1 was not related with the activity of a dietary histone deacetylase inhibitor of sulforaphane. ATF3 induction was detected from 2 hr after sulforaphane treatment, indicating that ATF3 could be a transcription factor to up-regulate NAG-1 expression. The results of this study may help to increase our understanding of the molecular mechanism of anti-cancer activity mediated by sulforaphane in human colorectal cancer cells.

Root Gravitropic Response of Phytochrome Mutant ( phyAB) in Arabidopsis

Phytochrome double mutant (phyAB) showed the delayed root gravitropic response compared to the wild type (WT) in Arabidopsis. After 8 hr of gravistimulation, the gravitropic response of mutant showed 48% of the WT. The delayed response started at 1.5 hr after gravistimulation. And we measured the ethylene production in the root segments of WT and mutant for 12 hr. Ethylene production of mutant decreased about 40% of the WT at 12 hr. This result suggested that the phytochrome might be linked with ethylene production in some way. Generally, ethylene inhibits the growth of plant organs including roots. We measured the root growth rate in the presence of ACC (1-aminocyclopropane-1-carboxylic acid), a precursor of ethylene. And WT showed the inhibition of root growth with ACC, but mutant did not show the inhibition as WT did. To confirm the relationship between the ethylene and gravitropic response, we measured the gravitropic response with ACC. In the presence of 10-6 M ACC, WT showed the 37.4% inhibition compared to the control (no ACC), whereas mutant showed the only 6.6% inhibition of control (no ACC). This research suggested the relationship between phytochrome and gravitropic response through an ethylene production.