Youn Young Hur

Gibberellin application at pre-bloom in grapevines down-regulates the expressions of VvIAA9 and VvARF7, negative regulators of fruit set initiation, during parthenocarpic fruit development.

Fruit set is initiated only after fertilization and is tightly regulated primarily by gibberellins (GAs) and auxins. The application of either of these hormones induces parthenocarpy, fruit set without fertilization, but the molecular mechanism underlying this induction is poorly understood. In the present study, we have shown that the parthenocarpic fruits induced by GA application at pre-bloom result from the interaction of GA with auxin signaling. The transcriptional levels of the putative negative regulators of fruit set initiation, including Vitis auxin/indole-3-acetic acid transcription factor 9 (VvIAA9), Vitis auxin response factor 7 (VvARF7), and VvARF8 were monitored during inflorescence development in seeded diploid ‘Tamnara’ grapevines with or without GA application. Without GA application, VvIAA9, VvARF7, and VvARF8 were expressed at a relatively high level before full bloom, but decreased thereafter following pollination. After GA application at 14 days before full bloom (DBF); however, the expression levels of VvIAA9 and VvARF7 declined at 5 DBF prior to pollination. The effects of GA application on auxin levels or auxin signaling were also analyzed by monitoring the expression patterns of auxin biosynthesis genes and auxin-responsive genes with or without GA application. Transcription levels of the auxin biosynthesis genes Vitis anthranilate synthase β subunit (VvASB1-like), Vitis YUCCA2 (VvYUC2), and VvYUC6 were not significantly changed by GA application. However, the expressions of Vitis Gretchen Hagen3.2 (VvGH3.2) and VvGH3.3, auxin-responsive genes, were up-regulated from 2 DBF to full bloom with GA application. Furthermore, the Vitis GA signaling gene, VvDELLA was up-regulated by GA application during 12 DBF to 7 DBF, prior to down-regulation of VvIAA9 and VvARF7. These results suggest that VvIAA9 and VvARF7 are negative regulators of fruit set initiation in grapevines, and GA signaling is integrated with auxin signaling via VvDELLA during parthenocarpic fruit development in grapevines.

Transcriptional analysis of Dehydrin1 genes responsive to dehydrating stress in grapevines

Dehydrins (DHNs) are proteins that are induced under dehydrating stress conditions such as drought, cold, and salinity. We investigated the expression of the DHN1 genes over time after drought treatment for 14 days and subsequent rehydration in the Korean native species, Vitis flexuosa, main cultivars ‘Campbell Early’ (Vitis spp.) and ‘Tamnara’ (Vitis spp.). Two highly homologous dehydrins, DHN1a and DHN1b, were isolated from ‘Campbell Early’ and ‘Tamnara’ grapevines, but only DHN1a cDNA was cloned from V. flexuosa leaves. Amino acid sequences of DHN1 deduced from five cDNAs of DHN1a/b from three grapevines were of the YSK2-type having the Y-, S-, and K-domain. Analysis of expression using quantitative real-time polymerase chain reaction and semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) revealed that expression of the DHN1a and DHN1b genes was induced earlier in V. flexuosa under drought stress conditions than in ‘Campbell Early’ and ‘Tamnara’. During drought stress, a large amount of DHN1a and DHN1b was continuously expressed. V. flexuosa could be a resource in stress-tolerant grape breeding for enhancing drought tolerance.

Characteristics of the Fruit Quality and Volatile Compounds of ‘Cheongsoo’ Grape by Treatment with Different Plant Growth Regulators

Wine grape is characterized by small berry-type fruits, which contain seeds and juicy pulp enclosed in thick skin. ‘Cheongsoo’, a Korean grape cultivar selected in 1995, is rich in flavor and used as both a wine and a table grape. The effects of growth regulator treatments including GA3 alone or in combination with thidiazuron (TDZ) or forchlorfenuron (FCF) have been studied in different Korean grape cultivars to select for traits such as seedless and firm fruits and to prevent berry shatter. However, growth regulators such as cytokines have been shown to delay the growth of grapes. Here, we assessed the effect of three growth regulators on ‘Cheongsoo’ grape through investigation of grape quality characteristics and the development of volatile flavor components. Three treatments of growth regulators, specifically 100ppm GA3 + 5ppm 1% TDZ, 100ppm GA3 + 5ppm 0.1% FCF and 100ppm GA3 alone, were applied at 14 days after full bloom while untreated grapes were used as control. Five quality characteristics of ‘Cheongsoo’ grape were investigated including the sugar, fatty acid and n-alkane contents, acidity and the degree of volatile compound production. Treatment with growth regulators resulted in greater average fruit weight of 6.30–6.48 g compared to the 4.49 g of untreated grapes. However, the sugar content of untreated grapes was 1°Brix higher (16.6 ± 0.55) than that of grapes treated with growth regulators. Similarly, the volatile compound and acid content of untreated grapes were elevated, with the latter being 0.67 ± 0.04% (w/v), which was 0.1% higher than grapes treated with growth regulators. The content of hexanal, (E)-2-hexenal, 4-hexen-1-ol, and (E)-2-hexen-1-ol derived from the C6 compounds and fatty acids were higher in grapes treated with growth regulators, also these compounds appeared abundant in immature fruits. The n-alkane content was more predominant in untreated grapes, mostly in the wax

Characteristics of aroma compounds of 11 red wines from international grape cultivars grown in Korea

The aroma compounds of 11 red wines grown and produced in Wanju region were characterized by headspacesolid phase microextraction combined with gas chromatography-mass spectrometry. Seventy-five aroma compounds were identified in the 11 red wines. The aroma compounds were grouped into five aroma series and their odor activity values were calculated to determine the aroma impact compounds in 11 wines. Alcohols, esters and C6 compounds were the main contributors to the aroma in the 11 wines. Isoamyl alcohol and phenylethyl alcohol obtained from the 11 red wines contributed to the floral, sweet, and fatty odorants in the wine. Octanoic acid ethyl ester, and hexanoic acid ethyl ester contributed to the fruity, floral, and sweet odorants of all the red wines. 1-Hexanol was detected all the wines, which contributed to the green odorant. The major aroma contribution of Chanceller, Malbec, Marchel, Narsha, Pinot Meunier, and Sangiovetto wines were the fruity series. The green series was the major contribution of the Cabernet Franc, Cabernet Sauvignon, and Sauvignon Vert wines. The floral series was the major contribution of the MBA and Narsha wines. Based on the results of these studies, aroma component analysis could be used as a selection criterion for developing wine cultivars.

Changes in aroma profile of korean grape cultivar 'doonuri' at different ripening stages

Grape aroma is formed by hundreds of volatile compounds of different chemical natures and origins, found at a wide range of concentrations. One of the most influential factors affecting the aroma characteristic of a grape is the stage of ripening of the grape. The concentration of varietal aroma compounds in grapes is influenced by several factors such as grape cultivar and degree of maturity, vintage, climate of the vineyard, and management techniques. The goal of the present work was to investigate the changes in volatile compounds occurring at different ripening stages (immature, veraison, maturation) of the ?Doonuri? cultivar. Six alcohols, 7 aldehydes, 11 esters, 5 ketones and lactones, and 2 other odor-active compounds were identified in grapes during ripening. The concentrations of aldehydes were highest during initial ripening. Ester, ketone, and lactone compounds formed primarily after veraison with a constant increase in levels during ripening and maturation. Ester, ketone, and lactone compounds in grape had higher odor activity values than other compounds. The flavor of the ?Doonuri? grape comes primarily from ester, ketone, and lactone compounds.