Sang-Gyu Seo

Cadmium resistance in tobacco plants expressing the MuSI gene.

MuSI, a gene that corresponds to a domain that contains the rubber elongation factor (REF), is highly homologous to many stress-related proteins in plants. Since MuSI is up-regulated in the roots of plants treated with cadmium or copper, the involvement of MuSI in cadmium tolerance was investigated in this study. Escherichia coli cells overexpressing MuSI were more resistant to Cd than wild-type cells transfected with vector alone. MuSI transgenic plants were also more resistant to Cd. MuSI transgenic tobacco plants absorbed less Cd than wild-type plants. Cd translocation from roots to shoots was reduced in the transgenic plants, thereby avoiding Cd toxicity. The number of short trichomes in the leaves of wild-type tobacco plants was increased by Cd treatment, while this was unchanged in MuSI transgenic tobacco. These results suggest that MuSI transgenic tobacco plants have enhanced tolerance to Cd via reduced Cd uptake and/or increased Cd immobilization in the roots, resulting in less Cd translocation to the shoots.

Gene expression profile affected by volatiles of new plant growth promoting rhizobacteria, Bacillus subtilis strain JS, in tobacco

Specific bacterial strains that promote plant growth have been investigated extensively and are characterized as plant growth-promoting rhizobacteria (PGPR). To identify the series of genes involved in PGPR-mediated enhanced plant growth, suppression subtractive hybridization was performed using cDNA from tobacco plants exposed to the PGPR strain, Bacillus subtilis strain JS. After hybridization, forward and reverse subtraction cDNA libraries containing 580 clones were obtained. Blastx search detected 170 single genes. These were classified into 14 functional categories, including metabolic processes and cellular processes implicated in growth promotion. Of the 36 responsive genes confirmed by RT-PCR, expression of 24 genes was up-regulated and 12 were down-regulated by treatment with B. subtilis JS volatile compounds. Photosynthesis pathway related genes encoding chlorophyll a/b binding protein, chloroplast sedoheptulose-1,7-bisphosphatase, and the photosynthate transport related gene were up-regulated, perhaps accounting for the volatile compound-mediated enhanced plant growth. Reactive oxygen species scavenging enzyme encoding genes as well as glutathione S-transferase and methionine-R-sulfoxide reductase were down-regulated.

Molecular cloning and expression analysis of Bro-GS-elong and Bro-myro from Brassica oleracea

The elongation factor GSL-Elong and myrosinase, which are essential for sulforaphane biosynthesis, were cloned for the first time from broccoli (Brassica oleracea var. italica) and were designated as Bro-GS-elong and Bro-myro. Sequence analysis of Bro-GS-elong and Bro-myro revealed that its full length cDNA was 1787 bp long and included a 1464 bp open reading frame encoding and 1846 bp long and included a 1647 bp open reading frame encoding, respectively. Bro-GS-elong and Bro-myro seem to be existed as members of multigene families in the broccoli genome and to be influenced by abiotic stresses and plant development. Bro-myro was preferentially expressed in reproductive organs, but the transcript levels of Bro-GS-elong were surpassed in vegetative organs. Both Bro-GS-elong and Bro-myro were strongly expressed at the period of sprouting, this result appeared to imply that Bro-GS-elong and Bro-myro may perform an important function in the early development on the quickly growing tissues and organs. The highest transcript levels of Bro-GS-elong and Bro-myro by MeJA treatment implied that glucosinolate-myrosinase system was primarily activated by jasmonates signaling. The results provide the basis for the glucosinolate-myrosinase system and the biotechnological manipulation of sulforaphane, a useful functional substance, in B. oleracea var. italica.

Current status on Miscanthus for biomass

Abstract The carbon dioxide concentration of the atmo-sphere is projected to increase by almost 50% over the first 50 years of this century. The major cause of this increase is continued combustion of fossil fuels. As a result, the sig-nificant changes in climate that have already occurred will be amplified, in particular a global temperature increase. Re-newable energy production has a central role to play in abating net CO 2 emissions to a level that will arrest the development of global warming. Especially, biomass crops are becoming increasingly important as concerns grow about climate change and the need to replace carbon dioxide- producing fossil fuels with carbon-neutral renewable sources of energy. To succeed in this role, biomass crop has to grow rapidly and yield a reliable, regular harvest. A prime candidate is Miscanthus , or Asian elephant grass, a perennial species that produces over 3 metres of bamboo-like stems in a year. Miscanthus species are typically diploid or tetraploid. Hybrids between species with different ploidy levels result in the highly productive triploid hybrids,

Alteration of floral organ identity by over-expression of IbMADS3-1 in tobacco

The MADS-box genes have been studied mainly in flower development by researching flower homeotic mutants. Most of the MADS-box genes isolated from plants are expressed exclusively in floral tissues, and some of their transcripts have been found in various vegetative tissues. The genes in the STMADS subfamily are important in the development of whole plants including roots, stems, leaves, and the plant vascular system. IbMADS3-1, which is in the STMADS subfamily, and which has been cloned in Ipomoea batatas (L.) Lam., is expressed in all vegetative tissues of the plant, particularly in white fibrous roots. Sequence similarity, besides the spatial and temporal expression patterns, enabled the definition of a novel MADS-box subfamily comprising STMADS16 and the other MADS-box genes in STMADS subfamily expressed specifically in vegetative tissues. Expression of IbMADS3-1 was manifest by the appearance of chlorophyll-containing petals and production of characteristic changes in organ identity carpel structure alterations and sepaloidy of the petals. In reverse transcription-polymerase chain reaction analysis with a number of genes known to be key regulators of floral organ development, the flowering promoter NFL1 was clearly reduced at the RNA level compared with wild type in transgenic line backgrounds. Moreover, NtMADS5 showed slight down-regulation compared with wild-type plants in transgenic lines. These results suggest that IbMADS3-1 could be a repressor of NFL1 located upstream of NtMADS5. IbMADS3-1 ectopic expression is suggested as a possible means during vegetative development by which the IbMADS3-1 gene may interfere with the floral developmental pathway.

Touch-induced gene (IbTCH1) from sweet potato [Ipomoea batatas (L.) Lam.]: molecular cloning and functional analysis

The cDNA of the touch-induced genes (TCH) of the sweet potato [Ipomoea batatas (L.) Lam.] has been cloned and analyzed. IbTCH1, which exists as at least two-copy genes in the genome of the sweet potato, encodes for 148-amino acid polypeptides, and harbors four conversed Ca2+-binding motif EF-hands. IbTCH1 was shown to be expressed in the flower, leaf, thick pigmented root, and particularly in the white fibrous root, but expressed only weakly in the petiole. IbTCH1 is upregulated upon exposure to environmental stresses, dehydration, and jasmonic acid. Furthermore, IbTCH1 is developmentally regulated in the leaf and root. These results strongly indicate that the gene performs functions in both plant development and in defense/stress-signaling pathways.

Overexpression of ADP-glucose pyrophosphorylase (IbAGPaseS) affects expression of carbohydrate regulated genes in sweet potato [Ipomoea batatas (L.) Lam. cv. Yulmi]

AbstractADP-glucose pyrophosphorylase is crucial in starch metabolism. The open reading frame of IbAGPaseS gene is comprised of 1539-base pairs and encodes a polypeptide of 512 amino acid residues. The deduced IbAGPaseS protein sequence was homologous with that of other AGPase proteins of various plant species. Also, the IbAGPaseS gene appears to be a member of multiple gene families and further, the differences in the copy numbers among the ten cultivars were considered to lead to differences in starch contents. IbAGPaseS was expressed in whole tissues and revealed high activity in thick-pigmented roots and developing tuberous roots. RT-PCR analysis indicated that the main role of IbAGPaseS is starch biosynthesis accumulating sink tissues during sweet potato root development. The IbAGPaseS cDNA was introduced to sweet potato under the control of the CaMV 35S promoter using Agrobacterium-mediated gene transfer techniques, thereby affecting the expression levels of carbohydrate regulated genes and sporamin gene. These results suggest that IbAGPaseS affects carbohydrate gene regulation.

An IbEF1 from sweet potato promotes flowering in transgenic tobacco

A novel gene, denoted IbEF1isolated from sweet potato corresponded to the most abundant mRNA present in root tissue under salt stress. However, the encoded protein did not accumulate in the shoots. Transgenic tobacco plants were generated to elucidate the physiological function of IbEF1. The extent of early flowering of these plants correlated well with the level of IbEF1 expression, implicating IbEF1 as a positive regulator of flowering of tobacco plants. Over-expression of IbEF1 enhanced the AP1 gene in response to flowering time, but not floral organ development. These results demonstrate that simple manipulation of IbEF1 activity has great potential with regard to flowering time.

Characterization and expression pattern of IbPRP1 and IbPRP2 stress-related genes from sweetpotato

Two putative stress-related genes were isolated from sweet-potato and were designated as IbPRP1 and IbPRP2 (Ipomoea batatas proline-rich proteins 1 and 2). The deduced amino acid aligment of IbPRP1 and IbPRP2 shows that these two genes belong to the AAI_LTSS superfamily. Proteins in this family are known to play primary roles including defending plants from pathogens and insects, lipid transport between intracellular membranes, and nutrient storage. The mRNA expression of IbPRP1 and IbPRP2 were investigated and the results demonstrate that IbPRP2 has tissue-specific expression. Moreover, IbPRP1 and IbPRP2 may be involved in response to various stresses including drought, pathogen, and oxidative stress. In addition, when leaf disc test was performed, the IbPRP1 transgenic tobacco plants showed increase in tolerance to salt (100 mM, 200 mM, and 300 mM). Moreover, IbPRP1 and IbPRP2 may have some roles of transmembrane protein in sweetpotato when checked through GFP fusion cell localization and transmembrane analysis. All of these results indicate that IbPRP1 and IbPRP2 might play an important role in plant stress responses.