Chung-Kyoon Auh

Phylogenetic analysis and inflow route of Tomato yellow leaf curl virus (TYLCV) and Bemisia tabaci in Korea

Tomato yellow leaf curl virus (TYLCV) is a member of the genus Begomovirus of the family Geminiviridae, members of which are characterized by closed circular single-stranded DNA genomes of 2.7-2.8 kb in length, and include viruses transmitted by the Bemisia tabaci whitefly. No reports of TYLCV in Korea are available prior to 2008, after which TYLCV spread rapidly to most regions of the southern Korean peninsula (Gyeongsang-Do, Jeolla-Do and Jeju-Do). Fifty full sequences of TYLCV were analyzed in this study, and the AC1, AV1, IR, and full sequences were analyzed via the muscle program and bayesian analysis. Phylogenetic analysis demonstrated that the Korea TYLCVs were divided into two subgroups. The TYLCV Korea 1 group (Masan) originated from TYLCV Japan (Miyazaki) and the TYLCV Korea 2 group (Jeju/Jeonju) from TYLCV Japan (Tosa/Haruno). A B. tabaci phylogenetic tree was constructed with 16S rRNA and mitochondria cytochrome oxidase I (MtCOI) sequences using the muscle program and MEGA 4.0 in the neighbor-joining algorithm. The sequence data of 16S rRNA revealed that Korea B. tabaci was closely aligned to B. tabaci isolated in Iran and Nigeria. The Q type of B. tabaci, which was originally identified as a viruliferous insect in 2008, was initially isolated in Korea as a non-viruliferous insect in 2005. Therefore, we suggest that two TYLCV Japan isolates were introduced to Korea via different routes, and then transmitted by native B. tabaci.

Expression Analysis of Proline Metabolism‐related Genes From Halophyte Arabis stelleri under Osmotic Stress Conditions

Arabis stelleri var. japonica evidenced stronger osmotic stress tolerance than Arabidopsis thaliana. Using an A. thaliana microarray chip, we determined changes in the expression of approximately 2 800 genes between A. stelleri plants treated with 0.2 M mannitol versus mock-treated plants. The most significant changes in the gene expression patterns were in genes defining cellular components or in genes associated with the endomembrane system, stimulus response, stress response, chemical stimulus response, and defense response. The expression patterns of three de novo proline biosynthesis enzymes were evaluated in A. stelleri var. japonica seedlings treated with 0.2 M mannitol, 0.2 M sorbitol, and 0.2 M NaCl. The expression of Δ¹ -pyrroline-5-carboxylate synthetase was not affected by NaCl stress but was similarly induced by mannitol and sorbitol. The proline dehydrogenase gene, which is known to be repressed by dehydration stress and induced by free L-proline, was induced at an early stage by mannitol treatment, but the level of proline dehydrogenase was increased later by treatment with both mannitol and NaCl. The level of free L-proline accumulation increased progressively in response to treatments with mannitol, sorbitol, and NaCl. Mannitol induced L-proline accumulation more rapidly than NaCl or sorbitol. These findings demonstrate that the osmotic tolerance of the novel halophyte, Arabis stelleri, is associated with the accumulation of L-proline.

RNA virus accumulation is inhibited by ribonuclease activity of 3D8 scFv in transgenic Nicotiana tabacum

Plant viruses continue to cause diseases on economically important crops. Therefore, numerous attempts to produce virus resistant plants have been reported by using the mechanisms such as host mediated protection and virus mediated protection. Here, a novel strategy of targeting viral RNA itself, rather than viral gene products, is presented to generate virus-resistant transgenic plants. A catalytic single chain variable antibody, 3D8 scFv, which has RNase activities, was functionally expressed in the cytosol of Nicotiana tabacum. We found that progenies of the transgenic tobacco plant acquired complete resistances against four ss-RNA tobamoviruses and one cucumovirus tested without viral accumulation and delayed onset of disease symptoms. The results showed that the resistance observed in 3D8 scFv transgenic plants was caused by the RNase activity of 3D8 scFv itself, not by RNA-mediated gene silencing mechanism. Taken together, we suggested that newly gained resistance of the 3D8 scFv transgenic plants to five ss-RNA viruses most likely resulted from the RNase activity of 3D8 scFv.

A nucleic acid hydrolyzing recombinant antibody confers resistance to curtovirus infection in tobacco

A catalytic single chain variable antibody (scFv), 3D8 scFv, which has DNase activities, was functionally expressed in Nicotiana tabacum. The subcellular localization of the GFP-fused 3D8 indicated that the 3D8 protein was expressed in the cytosol of the N. tabacum protoplasts. Progenies of the transgenic tobacco plants exhibited complete resistance against two single stranded (ss) DNA geminiviruses, including the Beet curly top virus and the Beet severe curly top virus, without viral accumulation or disease symptoms. We presented a novel strategy for targeting the viral DNA itself in a sequence non-specific manner, rather than the viral proteins or RNAs, in order to generate virus-resistant transgenic plants. No noticeable adverse effects on the growth and reproduction of the transgenic plants were observed. Our results demonstrated that targeting viral DNA is an effective strategy for protecting plants from ssDNA viruses.

Identification of natural weed hosts of Tomato chlorosis virus in Korea by RT-PCR with root tissues

Tomato chlorosis virus (ToCV) is a whitefly-transmitted crinivirus that causes interveinal chlorosis and bronzing on tomato leaves. Although outbreaks of ToCV have been reported in many countries, the virus was not reported in Korea until 2013. To identify weed hosts of ToCV that may serve as virus reservoirs, we analyzed various weeds that were growing together with ToCV-infected tomatoes and viruliferous Bemisia tabaci in a tomato greenhouse. We performed reverse transcription-polymerase chain reaction (RT-PCR) analysis of root samples from 148 samples of 61 species from 24 families of plants grown in the greenhouse to avoid possible ToCV contamination by whiteflies on leaves. Seventeen weed species were identified as ToCV hosts based on RT-PCR results of root samples: Conyza canadensis, Erigeron annuus, Sonchus asper, Youngia japonica, Trigonotis peduncularis, Cardamine flexuosa, Cerastium glomeratum, Stellaria media, Chenopodium album, Ipomoea hederacea, Quamoclit coccinea, Vicia angustifolia var. segetilis, V. tetrasperma, Phytolacca americana, Mazus pumilus, Solanum americanum and S. nigrum. The amplicons obtained by RT-PCR were confirmed as ToCV by sequence analysis. Life cycle analysis of the weeds indicated that each weed could play an important role as a “green bridge” or virus reservoir between tomato cultivation seasons. This is the first report documenting the possible occurrence of ToCV in tomato plants based on weed life cycles.

Agroinoculation of Nicotiana benthamiana with cloned honeysuckle yellow vein virus isolated from Lonicera japonica

A new honeysuckle yellow vein geminivirus (HYVV) isolate (2,763 nucleotides) and the HYVV-β satellite (1,227 nucleotides) from Korea were cloned and characterized from symptomatic leaves of Lonicera japonica with a yellow net mosaic appearance. Phylogenetic analysis of HYVV and 13 other begomoviruses revealed that HYVV has the highest nucleotide sequence homology to HYVV-UK2. Grafting challenge of a virus-free L. japonica (scion) on an HYVV-infected L. japonica (stock) resulted in the appearance of typical HYVV disease symptoms on the newly developed leaves of the scion. Two pMon521 plasmids containing 1.3 copies and 2.0 copies of the cloned HYVV isolate, respectively, were infectious and produced disease symptoms in Nicotiana benthamiana after agroinoculation. We conclude that the causal agent of yellow net mosaic in L. japonica is a new Korean isolate of HYVV, based on sequence comparisons, agroinoculation-induced disease symptoms, electron microscopy, and phylogenetic analysis.

Mineral-rich Solar Sea Salt Generates Less Oxidative Stress in Rats than Mineral-deficient Salt

Certain solar sea salts have a high content of essential minerals other than NaCl. The effects of minerals in sea salts on oxidative stress in rats were investigated. Mineral-rich salt (MRS) and mineral-deficient salt (MDS) did not scavenge DPPH radicals. When MRS and MDS (equivalent to 1.8 g NaCl/kg/day) and a saline control were orally administered to rats for 7 weeks, MRS group rats showed lower levels of plasma lipid oxidation than MDS group rats. MRS group rats exhibited significantly lower levels of protein carbonyls and 8-hydroxy-2′-deoxyguanosine in the liver than MDS group rats. MRS group rats showed lower protein expression of NF-κB p65 in adipose tissue than MDS group rats. Intake of MRS may generate less oxidative stress than intake of MDS.

Phylogenetic lineage of Tobacco leaf curl virus in Korea and estimation of recombination events implicated in their sequence variation

New strains of Tobacco leaf curl virus (TbLCV) were isolated from tomato plants in four different local communities of Korea, and hence were designated TbLCV-Kr. Phylogenetic analysis of the sequences of the whole genome and of individual ORFs of these viruses indicated that they are closely related to the Tobacco leaf curl Japan virus (TbLCJV) cluster, which includes Honeysuckle yellow vein virus (HYVV), Honeysuckle yellow vein mosaic virus (HYVMV), and TbLCJV isolates. Four putative recombination events were recognized within these virus sequences, suggesting that the sequence variations observed in these viruses may be attributable to intraspecific and interspecific recombination events involving some TbLCV-Kr isolates, Papaya leaf curl virus (PaLCV), and a local isolate of Tomato yellow leaf curl virus (TYLCV).

Phenolic Contents and Antioxida nt Activities of Six Edible Seaweeds

Abstract Phenolic contents and antioxidant activities were determined in the water and ethanol extracts from six species ofedible seaweeds, Phaeophyceae ( Laminaria japonica, Hizikia fusiformis and Undaria pinnatifida ), Rhodophyceae ( Porphyra tenera and Gracilaria verrucosa ) and Chlorophyceae ( Ulva lactuca ). The highest extraction yield was observed in water extract (pH 8.0) of G. verrucosa (44.23 %) and phenolic content was the highest in ethanolic (75%) extract of H. fusiformis (52.82 μg/mg). 25 % ethanolic extract from U. lactuca was found to have the highest DPPH radicals scavenging activity(19.29 %) and superoxide anion scavenging activitiy was higher in water extract (pH 8.0) from H. fusiformis (81.20 %) than that other seaweeds. Phenolic contents were strongly correlated with antioxidant activity in the six edible seaweeds extracts (R 2 =0.852). Taken together, these results indicate that H fusiformis may be a excellentsource for development of natural antioxidants. Key Words :

Expression analysis of D-type cyclin in potato (Solanum tuberosum L.) under different culture conditions

Key messageTaken together, this study suggests that potato D-type cyclin genes are expressed differentially between in vitro and planta caused by intrinsic differences in physiology and gene action at the cellular and whole organism levels.AbstractCyclin performs a pivotal role in control of the cell cycle by forming a complex with cyclin-dependent kinases (CDKs). In this study, the potato cyclin D3 genes (StCycD3.1, StCycD3.2, and StCycD3.3) were isolated and analyzed. A sequence analysis showed that the potato cyclin D3 genes shared high levels of sequence homology with tomato cyclin D3 genes. The potato cyclin D3 genes revealed organ-specific expression; StCycD3.1 was strongly expressed in above-ground organs, whereas StCycD3.2 was strongly expressed in underground organs. The expression patterns of the potato cyclin D3 genes were analyzed under a variety of environmental conditions such as different carbon sources and hormones. Glucose (as a carbon source) and zeatin (as a hormone) were effective single factors for increasing potato cyclin D3 expression. Sucrose and zeatin were the most effective combination for high-level induction of the genes. Time-course-based gene expression patterns were evaluated in treatments of leaf explants with combinations of different light conditions and hormones. The potato cyclin D3 genes were expressed abundantly in the presence of hormones during the late stage of long-term dark conditions. The gene expression patterns were also monitored in entire potato plants under different light conditions. The gene expression levels were consistently low under the different light regimes but potato cyclin D3 genes were up-regulated during a shift in illumination from dark to light.