Seong Heo

Identification of S-allele genotypes of Korean apple cultivars by using allele-specific polymerase chain reaction

By using allele-specific polymerase chain reaction, self-incompatibility (S)-genotypes of the Korean apple cultivars were analyzed to identify their self-incompatibility relationship. S-genotypes of the cultivars were determined as ‘Hongro’, ‘Saenara’, ‘Hongso’, and ‘Hongan’, S1S3; ‘Picnic’, S1S5; ‘Gamhong’, ‘Manbok’, ‘Hwarang’, ‘Yeohong’, ‘Danhong’, and ‘Hwayoung’, S1S9; ‘Seokwang’, S3S5; ‘Honggeum’ and ‘Greenball’, S3S7; ‘Sunhong’, ‘Seohong’, ‘Chukwang’, and ‘Hwahong’, S3S9; and ‘Summer Dream’, S7S9. These results will help to select compatible pollinizers and design apple orchards.

Structure and expression of MdFBCP1, encoding an F-box-containing protein 1, during Fuji apple (Malus domestica Borkh.) fruit ripening

From database comparisons of 1,117 expressed sequence tags (ESTs) generated from ripened Fuji apple fruits, we identified ten ubiquitin (Ub)-related genes. RNA gel-blot analysis suggests that these Ub-related genes are induced by at least four distinct signaling pathways in fruits. In this study, we analyzed structure and expression of MdFBCP1, encoding an F-box-containing protein 1, in Fuji apples. MdFBCP1 transcript was predominantly expressed in the fully ripened climacteric fruits, in which serge of ethylene production occurred. The MdFBCP1 gene was also activated effectively in response to exogenous ethylene treatment, with the induction pattern being comparable to those of ACC oxidase and β-cyanoalanine synthase. Thus, it seems likely that the expression of MdFBCP1 is closely associated with a climacteric ethylene production and ACC oxidase activity and, hence, MdFBCP1 may play a role in the ripening process of Fuji apple fruits. Yeast two hybrid and in vitro pull-down assays revealed that MdFBCP1 physically interacted with MdSkp1 and N-terminal F-box motif was essential for this interaction. These results suggest that MdFBCP1 indeed functions as an F-box-containing protein and participates in the formation of SCF complex, which acts as E3 Ub ligase. Genomic Southern blot analysis showed that MdFBCP1 exhibited different pattern of restriction enzyme digestion in three cultivars (Tsugaru, Golden Delicious and Fuji) that produce different amount of ethylene, suggesting that the MdFBCP1 gene is organized in a cultivar specific manner. Collectively, our data suggest that Ub degradation pathway may play an important role in the ripening of Fuji apple fruits.

Occurrence of Apple Scar Skin viroid and Relative Quantity Analysis Using Real-time RT-PCR

Apple scar skin viroid (ASSVd) is one of the smallest viral pathogens infecting fruits, especially apple, and causes a significant damage to fruit trees. ASSVd usually induced the skin-dapple ring symptoms, but in `Fuji` varieties, corked spot were occurred on the fruit skin in 2009. This new symptom will be of great helpful to diagnosis ASSVd in sight. ASSVd was surveyed in apple and pear from 2009 to 2010 in Korea, and ASSVd was identified in 20 out of 1,193 trees. The infection rate was 1.7%. To screen the infectivity of ASSVd among apple cultivars, real-time RT-PCR was applied followed by designing of ASSVd specific primers based on highly conserved regions of several ASSVd isolates including Korean isolate. NADH dehydrogenase subunit 5 (nad 5) gene, which is mRNA of the mitochondrial gene, was used for internal control. In this study, ASSVd infected apples were classified into 12 groups depending on different symptoms and symptom severity (scaring, rusting or malformation). Taken together, this study suggested that real-time PCR analysis was more sensitive to detect the low copy of ASSVd on early viroid infected apple skins than regular RT-PCR method.

Isolation and characterization of genes expressed differently in mature fruits of ‘redfield’ and ‘greensleeves’ apples

Anthocyanins are responsible for most of the bright red and blue colors found in higher plants. Anthocyanin accumulation is regulated by MYB transcription factors. Some varieties of apple indicate anthocyanin accumulation with a red color in the skin and, at times, even in the cortex core, but other varieties without anthocyanin production have green-colored skin indicative of chlorophyll accumulation. To obtain gene expression profiles from the apple cultivars with different flesh and skin colors, 2 apple cultivars, the red-colored ‘Redfield’ and the green-colored ‘Greensleeves’, were used. A cDNA suppression subtractive hybridization library was established and analyzed. Six genes encoding methallothionein-like protein, chalcone isomerase, dirigent-like protein, brassinosteroid-6-oxidase, an unnamed protein product, and some unknown proteins were selected, and their expression was confirmed in the ‘Redfield’ cultivar through virtual northern blot analysis. In the ‘Greensleeves’ cultivar, 5 genes encoding gibberellins-regulated protein, a hypothetical 23.5 KD protein, anthranilate N-hydroxycinnamoyl/benzoyltransferase, and isoflavone reductase were chosen, and their upregulated transcriptional levels were identified. These selected genes were differently expressed in each apple cultivar, suggesting that these genes directly or indirectly regulate anthocyanin accumulation.

Characterization of Prunus necrotic ringspot virus Isolate from Peach in Korea

In this paper, we report a characterization of Prunus necrotic ringspot virus (PNRSV) isolate. The virus was identified from `Yumyeong` peach showing mild mosaic on leaves in commercial orchard of `Umsung`, Chungbuk province in Korea. The virus isolate produced ringspot symptom on the inoculated cotyledons and systemic mosaic and malformation on the upper leaves of Cucumis sativus. Systemic mottles were appeared in Chenopodium quinoa. When the buds of the virus infected stem were grafted on the healthy young Prunus persica GF305 seedlings, line pattern with mosaic appeared within 3 months. Isometric virus-like particles were found in parenchyma cells and plasmodesmata of C. sativus leaves inoculated mechanically with the virus. The cDNA fragments of PNRSV coat protein (CP) region, approximately 675bp, were synthesized from genomic RNA extracted from virus-infected leaves by RT-PCR using specific primer pairs. Partial nucleotide sequences of the CP regions were determined and analyzed with the known PNRSV. The CP gene of PNRSVKorea isolates showed 93.9~94.7% similarity to the 4 known PNRSV isolates.