Hyun-Ah So

Hypolipidemic effect of Salicornia herbacea in animal model of type 2 diabetes mellitus

To control blood glucose level as close to normal is a major goal of treatment of diabetes mellitus. Hyperglycemia and hyperlipidemia are the major risk factors for cardiovascular complications, the major cause of immature death among the patients with type 2 diabetes. The purpose of this study is to determine the hypoglycemic and hypolipidemic effects of Salicornia herbacea in animal model of type 2 diabetes and to investigate the possible mechanisms for the beneficial effects of S. herbacea. S. herbacea was extracted with 70% ethanol and desalted with 100% ethanol. Three week-old db/db mice (C57BL/KsJ, n=16) were fed AIN-93G semipurified diet or diet containing 1% desalted ethanol extract of S. herbacea for 6 weeks after 1 week of adaptation. Fasting plasma glucose, triglyceride, and total cholesterol were measured by enzymatic methods and blood glycated hemoglobin (HbA1C) by the chromatographic method. Body weight and food intake of S. herbacea group were not significantly different from those of the control group. Fasting plasma glucose and blood glycated hemoglobin levels tended to be lowered by S. herbacea treatment. Consumption of S. herbacea extract significantly decreased plasma triglyceride and cholesterol levels (p<0.05). The inhibition of S. herbacea extract against yeast α-glucosidase was 31.9% of that of acarbose at the concentration of 0.5 mg/mL in vitro. The inhibitory activity of ethanol extract of S. herbacea against porcine pancreatic lipase was 59.0% of that of orlistat at the concentration of 0.25 mg/mL in vitro. Thus, these results suggest that S. herbacea could be effective in controlling hyperlipidemia by inhibition of pancreatic lipase in animal model of type 2 diabetes.

Molecular Cloning and Characterization of Soybean Cinnamoyl CoA Reductase Induced by Abiotic Stresses

National Academy of Agricultural Science, RDA, Suwon 441-707, Korea (Received on August 10, 2010; Accepted on October 26, 2010)Suppression subtractive hybridization was used toisolate wound-induced genes from soybean. One of thewound-induced genes, gmwi143 designated as GmCCR,showed high homology with genes encoding cinnamoyl-CoA reductase (CCR; EC 1.2.1.44). Deduced aminoacid sequences encoded by GmCCR showed the highestidentity (77%) with those of Acacia CCR. There are 2CCR genes highly homologous to GmCCR in soybeangenome based on Phytozome DB analysis. RNA expre-ssion of GmCCR was specifically induced by local andsystemic wounding, drought, high salinity or by ultra-violet stress. Our study suggests that GmCCR may beinvolved in resistance mechanism during abiotic stressesin plants. Keywords :cinnamoyl-coA reductase, lignin, soybean, wound-ing, UVLignin, a major component of secondary cell walls, isdeposited mainly in the vascular tissues during plantdevelopment and environmental signals (Boerjan et al.,2003). Lignins contribute to major functions in plants, suchas stem rigidity, water transport in xylem and are alsoinvolved in defense reactions against wounding, predatorsor pathogens (Vance et al., 1980). It has been reported thatlignin biosynthesis is regulated by developmental signal inthe vascular tissues and by defense responses in plant(Lauvergeat et al., 2001).The biosynthesis of lignins begins with the commonphenylpropanoid pathway, starting from phenylalanine andleading to cinnamoyl CoAs which are the common pre-cursors of a wide range of phenolic compounds. These CoAesters subsequently are changed to monolignols via tworeductive steps catalyzed by cinnamoyl CoA:NADP oxido-reductase (CCR, EC 1.2.1.44) and cinnamyl alcohol de-hydrogenase (CAD, EC 1.1.1.195). Lignins result from theoxidative polymerization of monolignols. Several genes encoding CCR have been shown to betranscriptionally induced by developing xylem tissues or bybiotic stress (Kim et al., 2000; Lacombe et al., 1997;Lauvergeat et al., 2001). Lacombe et al. (1997) showed thatEucalyptus CCR transcript was expressed in lignified organssuch as leaves, stems and roots. By in situ hybridizationtechnique, EuCCR was strongly expressed in the differ-entiating xylem zone but was not present in the secondaryphloem fibers or in the young periderm (Lacombe et al.,1997). Rice OsCCR1 RNA expression was induced insuspension cell cultures treated with sphingolipid elicitorpurified from rice blast Magnaporthe grisea (Kawasaki etal., 2006). Previously, soybean chip analysis showed thatRNA expression of CCR invovled in phenylpropanoidpathway were induced in the syncytia laser microdissectedsoybean roots infected with soybean cyst nematode (Klinket al., 2009).There are 11 putative CCR homologues sharing homo-logy identities raging from 82.8 to 32.8% in Arabidopsisgenome (Costa et al., 2003). Arabidopsis AtCCR1 transcriptwas expressed in the stem and floral tissues (Lauvergeat etal., 2001) and the irregular xylem4 mutant (irx4) defectivein the AtCCR1 gene showed severely reduced lignin con-tents (50%) compared to the wild type (Jones et al., 2001).Lauvergeat et al. (2001) suggested that AtCCR2 responsiveto pathogen infection of Xanthomonas campestris pv.campestris may play a role in the formation of phenoliccompounds associated with HR in Arabidopsis (Lauvergeatet al., 2001). In the present study, we have isolated the full-lengthcDNA of GmCCR encoding CCR-like protein regulated byabiotic stresses. We propose that the GmCCR is involved indefense responses during environmental stresses in plants.

Molecular characterization of a 2-Cys peroxiredoxin induced by abiotic stress in mungbean

A mungbean low temperature-inducible VrPrx1 encoding 2-Cys peroxiredoxin (2-Cys Prx) was cloned by subtractive suppression hybridization. The deduced VrPrx1 amino acid sequence showed highest sequence homology to 2-Cys Prxs of Phaseolus vulgaris (95%), Pisum sativum (89%), and Arabidopsis thaliana (87%). VrPrx1 RNA and protein levels were increased by low temperature, hydrogen peroxide (H2O2), and wounding but decreased by high salinity, drought, and exogenous abscisic acid. Recombinant His-tagged VrPrx1 recombinant protein protected DNA and glutamine synthetase activity from degradation via the thiol/Fe(III) oxygen mixed-function oxidation system, and exhibited peroxidase activity to H2O2 in the presence of the reducing agent dithiothreitol (DTT) in vitro. The oxidized dimers and oligomers of the VrPrx1 recombinant protein were reduced to monomers by DTT or thioredoxin. Subcellular localization studies confirmed that VrPrx1-GFP was targeted to the plastid. To evaluate the function of VrPrx1in planta, the antioxidant activities and photosynthetic efficiency were investigated in VrPrx1-overexpressing Arabidopsis plants. VrPrx1 ectopic expression conferred improved photosynthetic efficiency under oxidative stress conditions. Hence, mungbean VrPrx1 may play an important role in protecting the photosynthetic apparatus against oxidative and abiotic stress conditions.

RsERF1 derived from wild radish (Raphanus sativus) confers salt stress tolerance in Arabidopsis

The change in environmental parameters affects normal growth of plants, eventually reduces agricultural production. Ethylene plays vital roles in plant stress responses, germination, fruit ripening, organ abscission, pathogen response, and senescence. Expression of an ethylene-responsive transcription factor (ERF) was induced in Korean halophyte, Raphanus sativus var. hortensis f. raphanistroides (wild radish) by 200-mM sodium chloride (NaCl). Raphanus sativus ethylene-responsive transcription factor 1 (RsERF1) is also localized to nucleus, similar to other transcription factors. In yeast, RsERF1 showed transcriptional activation property, by expressing the reporter gene. Being a TF, RsERF1 specifically bound to the cis-acting elements, GCC box and DRE/CRT in vitro, to initiate transcription. Homozygous T3 transgenic Arabidopsis, overexpressing RsERF1, showed significant tolerance against salt stress in soil-grown conditions. The tolerance was also marked by an increased germination rate of RsERF1 transgenics in salt-containing media. In RsERF1 overexpression lines, abiotic stress-related genes such as ABF3, ABF4, ADH, Rab18, and SUS1 were upregulated by 200-mM NaCl. ERFs have been studied and proven for their tolerance potential against various abiotic stresses, but RsERF1 belongs to an ERF subgroup called ethylene-responsive transcription factor related to AP2 (ERF-RAP2). Thus, this is a first report for ERF-RAP2 from Korean halophyte cDNA library. We believe that extensive posttranslational modification studies will reveal the role and location of RsERF1 in stress tolerance pathway.

Molecular cloning and characterization of RNA binding protein genes from the wild radish

Two cDNA clones encoding RNA binding proteins (RBPs) were isolated from a cDNA library constructed from salt-treated leaf tissues of wild radish (Raphanus sativus var. hortensis for raphanistroide). The deduced amino acid sequence of either RsRBP1 or RsGRP1 contains an RNA-recognition motif (RRM) at the carboxy or amino terminal. Comparative sequence analysis of RsRBP1 reveals extensive homology (63–84%) to known RBPs from other plants. RsGRP1 was shown to be most homologous to AtGRP7 (93%) out of eight members of Arabidopsis glycine-rich RBPs. Transcript levels of RsRBP1 was up-regulated slowly and reached its maximum at 9 h during salt stress. On the other hand, RNA expression of RsGRP1 was up-regulated rapidly but significantly was reduced at 9 h after salt stress. The RsRBP1 and RsGRP1 proteins were detected in the nucleus and cytoplasm. Characterization of the transgenic Arabidopsis plants overexpressing RsRBP1 and RsGRP1 revealed that both transgenic lines displayed enhanced growth under the osmotic stress conditions. Overexpression of RsGRP1 resulted in delayed germination rates under the osmotic stress conditions, whereas RsRBP1 overexpression Arabidopsis did not display any difference in germination rates during osmotic stress. These results suggest that RsRBP1 and RsGRP1 may be involved in the responses to osmotic stress in plant.