Kee-Young Kim

Flow karyotypes and chromosomal DNA contents of genus Triticum species and rye (Secale cereale)

The flow cytometry and chromosome imaging method were jointly used for analyzing genome content and chromosomal DNA content of hexaploid wheat (AABBDD), hexaploid triticale (AABBRR), tetraploid wheat (AABB), and AA, BB, DD genome donors and RR genome rye. Their genome sizes were 34.4 pg, 40.9 pg, 26.2 pg, 12.1 pg, 13.7 pg, 10.5 pg, and 16.9 pg, respectively. The 2C nuclear DNA content of BB genome donor with 13.7 pg was the highest value among the other genome donors, AA or DD. The genome content of tetraploid wheat, unlike hexaploid wheat or hexaploid triticale, was larger than the sum of the genomes of AA and BB genome donors. The DNA content of each chromosome ranged from 1.22 pg in DD genome donor to 2.61 pg in rye. Each chromosome peak was divided into three to four groups. Only one chromosome was included in the highest chromosomal DNA peak in hexaploid wheat, tetraploid wheat, DD genome donor and rye but two chromosomes in AA, BB genome donors, and hexaploid triticale. Correlation between 2C nuclear DNA content and chromosome density volume was the highest value compared with the other chromosomal parameters of chromosome area, or chromosome length.

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 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.

Isolation of cDNA Encoding Low Temperature-inducible L-asparaginase from Soybean (Glycin max)

Suppression subtractive hybridization (SSH) was used to isolate wound-induced cDNAs from wounded soybean. One of low-temperature-inducible cDNA, slti182 showed high homology with genes encoding 1-asparaginase. The full length cDNA of slti182, deginated GmASP1, is 1258 bp long and contains an open reading frame consisted of 326 amino acids. CmASP1 protein showed the highest identity (84%) with putative asparaginase from A. thaliana (AB012247), but it showed only 55% identity with another isoform of A. tathaliana (Z34884). The expression of GmASP1 during low temperature stress started to increase 3 hours after treatment, reached the maximum at 6 hour, and then decreased to the initial level at 48 hours. The amount of GmASP1 transcripts increased again when low-temperature-treated plants were transferred to room temperature, The present study suggests that GmASP1 may function to accelerate the protein synthesis which is important in the early response to low temperature.