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L-ascorbic acid (Vitamin C, AsA) is an important component of human nutrition. Plants and several animals can synthesize their own ascorbic acid, whereas humans lack the gene essential for ascorbic acid biosynthesis and must acquire from their diet. In the present study, we developed transgenic potato (Solanum tuberosum L. cv. Taedong Valley) over-expressing L-gulono-gamma-lactone oxidase (GLOase gene; NCBI Acc. No. NM022220), isolated from rat cells driven by CaMV35S constitutive promoter that showed enhanced AsA accumulation. Molecular analyses of four independent transgenic lines performed by PCR, Southern and RT-PCR revealed the stable integration of the transgene in the progeny. The transformation frequency was ca. 7.5% and the time required for the generation of transgenic plants was 6-7 weeks. Transgenic tubers showed significantly enhanced AsA content (141%) and GLOase activity as compared to untransformed tubers. These transgenics were also found to withstand various abiotic stresses caused by Methyl Viologen (MV), NaCl or mannitol, respectively. The T(1) transgenic plants exposed to salt stress (100 mM NaCl) survived better with increased shoot and root length when compared to untransformed plants. The elevated level of AsA accumulation in transgenics was directly correlated with their ability to withstand abiotic stresses. These results further demonstrated that the overexpression of GLOase gene enhanced basal levels of AsA in potato tubers and also the transgenics showed better survival under various abiotic stresses.

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Simple sequence repeats (SSRs) derived from expressed sequence tags (ESTs) are important resources for gene discovery and mapping. In this study, we developed EST-based SSR (eSSRs) markers and assessed their ability in mapping and transferability. A total of 10 800 unigenes were detected from 18 522 pea EST sequences (December 2009). Screening of 10 800 unigenes by MISA (MIcroSAtellite) revealed 2612 (14.1%) eSSRs in 2395 (12.9%) SSR-containing ESTs from which 577 (24.1%) primer pairs were designed. The most abundant repeat motif identified in eSSR was mononucleotide (85.2%), followed by trinucleotide (10.6%) and dinucleotide (2.8%). Among 108 randomly selected primer pairs, 40 were assessed for mapping and 68 to test cross-species transferability in six leguminous species. Out of 40 primer pairs, 85% produced amplicons, 60% showed polymorphism and 47.5% were mapped. Furthermore, 68 primer pairs revealed high rate of transferability (48-85%) in leguminous species. High levels of polymorphism, reproducibility, presence of alleles (3.8/locus) and transferability revealed the potential use of these eSSR markers in molecular mapping, quantitative trait loci (QTL) analysis and comparative mapping in pea and other legumes.