We have isolated a full-length cDNA, PPI1 (pepper-PMMV interaction 1), encoding a novel basic region-leucine zipper (bZIP) DNA-binding protein, from expressed sequence tags differentially expressed in Capsicum chinense PI257284 infected with Pepper mild mottle virus (PMMV). PPI1 encodes a predicted protein of 170 amino acids and contains a putative DNA-binding domain that shares significant amino acid identity with ACGT-binding domains of members of the bZIP DNA-binding protein family. PPI1 was localized in the nucleus and had transcriptional activation activity in yeast. Transcripts of the PPI1 gene were preferentially induced during an incompatible interaction by inoculation with PMMV, Pseudomonas syringae pv. syringae 61, and Xanthomonas campestris pv. vesicatoria race 3. However, the PPI1 gene was not induced by abiotic stressors that activate the plant defense-signaling pathway. Our data provide the first evidence that a bZIP transcription factor is preferentially induced by pathogen attack, suggesting that PPI1 may play a specific functional role in the regulation of expression of plant defense-related genes.

In watermelon, grafting of seedlings to rootstocks is necessary because watermelon roots are less viable than the rootstock. Moreover, commercially important watermelon varieties require disease-resistant rootstocks to reduce total watermelon yield losses due to infection with viruses such as cucumber green mottle mosaic virus (CGMMV). Therefore, we undertook to develop a CGMMV-resistant watermelon rootstock using a cDNA encoding the CGMMV coat protein gene (CGMMV-CP), and successfully transformed a watermelon rootstock named 'gongdae'. The transformation rate was as low as 0.1-0.3%, depending on the transformation method used (ordinary co-culture vs injection, respectively). However, watermelon transformation was reproducibly and reliably achieved using these two methods. Southern blot analysis confirmed that the CGMMV-CP gene was inserted into different locations in the genome either singly or multiple copies. Resistance testing against CGMMV showed that 10 plants among 140 T1 plants were resistant to CGMMV infection. This is the first report of the development by genetic engineering of watermelons resistant to CGMMV infection.

We used two genes, TMV-CP and PPI1 (pepper-PMMV interaction 1 transcription factor), to transform commercially important chili pepper (Capsicum annuum) inbred lines (P915, P409) by means of Agrobacterium co-culture. Eighteen independently transformed T0 plants were obtained. The most critical point in the pepper transformation protocol was the selection of shoots growing on calli--referred to as callus-mediated shoot formation (indirect shooting)--because shoots not grown from the callus (direct shooting from the wounded surface) developed into non-transformants. Selection of the correct right callus type also proved to be an important requirement for obtaining transformed peppers. Six different types of callus developed during the selection process. Shoots regenerated from two of these types, while one type regenerated significantly more shoots than the other types, suggesting that the capacity for shoot formation is callus type-specific. Although the transformation rate was low, transformation via callus-mediated shoot formation proved to be reproducible and was confirmed by Southern and Northern blot analyses. Based on the experimental data, we have succeeded in developing a new protocol for the selection and transformation of pepper and expect that it will be used in the future for pepper transformation.

SSR markers were used for variety discrimination and genetic assessment in watermelon varieties. Genetic characterization of 49 watermelon varieties was investigated using 30 SSR markers developed from melon and watermelon. A total of 121 polymorphic amplified fragments were obtained by using 30 SSR markers. The average polymorphism information content (PIC) was 0.502 ranging from 0.223 to 0.800. One hundred twenty one SSR loci were used to calculate Jaccard's distance coefficients for unweighted pair group method using the arithmetic averages (UPGMA) cluster analysis. A clustering group of varieties, based on the results of SSR analysis, were categorized into 5 major groups corresponding to morphological traits. Inheritance mode of 2 SSR markers was investigated to F1 plants and F2 populations of 2 crosses. Parental alleles were transmitted from F1 plants and F2 populations. Therefore, these marker sets may prove to be effectively applicable to genetic assessment of germplasm, genome mapping, and fingerprinting of watermelon varieties.

Mature zygotic embryos dissected from ginseng (Panax ginseng C.A. Meyer) seeds were cultured on Murashige and Skoog (MS) medium containing various concentrations of 2,4-D and kinetin. Somatic embryos were induced directly from cotyledonary tissue and from intervening callus. The frequency of somatic embryo induction was up to 55% of zygotic embryo explants. Upon transfer onto half-strength MS medium supplemented with 1 mg BA/liter and 1 mg GA3/liter, most somatic embryos developed into plantlets. More than 50% of the plantlets flowered after 4 weeks of culture, and some developed immature fruits in vitro. These results indicate that adulthood of ginseng root explants is not a prerequisite for flowering of plantlets regenerated through somatic embryogenesis. Chemical names used: (2,4 -dichlorophenoxy) acetic acid (2,4-D); N-(2-furanylmethyl) -1H-purin-6-amine(kinetin); N-(phenylmethyl) -1H-purin-6-amine (BA); gibberellic acid (GA3).