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1.  Transgenic Alfalfa Plants Expressing the Sweetpotato Orange Gene Exhibit Enhanced Abiotic Stress Tolerance 
PLoS ONE  2015;10(5):e0126050.
Alfalfa (Medicago sativa L.), a perennial forage crop with high nutritional content, is widely distributed in various environments worldwide. We recently demonstrated that the sweetpotato Orange gene (IbOr) is involved in increasing carotenoid accumulation and enhancing resistance to multiple abiotic stresses. In this study, in an effort to improve the nutritional quality and environmental stress tolerance of alfalfa, we transferred the IbOr gene into alfalfa (cv. Xinjiang Daye) under the control of an oxidative stress-inducible peroxidase (SWPA2) promoter through Agrobacterium tumefaciens-mediated transformation. Among the 11 transgenic alfalfa lines (referred to as SOR plants), three lines (SOR2, SOR3, and SOR8) selected based on their IbOr transcript levels were examined for their tolerance to methyl viologen (MV)-induced oxidative stress in a leaf disc assay. The SOR plants exhibited less damage in response to MV-mediated oxidative stress and salt stress than non-transgenic plants. The SOR plants also exhibited enhanced tolerance to drought stress, along with higher total carotenoid levels. The results suggest that SOR alfalfa plants would be useful as forage crops with improved nutritional value and increased tolerance to multiple abiotic stresses, which would enhance the development of sustainable agriculture on marginal lands.
PMCID: PMC4422619  PMID: 25946429
2.  Stable Internal Reference Genes for the Normalization of Real-Time PCR in Different Sweetpotato Cultivars Subjected to Abiotic Stress Conditions 
PLoS ONE  2012;7(12):e51502.
Reverse transcription quantitative real-time PCR (RT-qPCR) has become one of the most widely used methods for gene expression analysis, but its successful application depends on the stability of suitable reference genes used for data normalization. In plant studies, the choice and optimal number of reference genes must be experimentally determined for the specific conditions, plant species, and cultivars. In this study, ten candidate reference genes of sweetpotato (Ipomoea batatas) were isolated and the stability of their expression was analyzed using two algorithms, geNorm and NormFinder. The samples consisted of tissues from four sweetpotato cultivars subjected to four different environmental stress treatments, i.e., cold, drought, salt and oxidative stress. The results showed that, for sweetpotato, individual reference genes or combinations thereof should be selected for use in data normalization depending on the experimental conditions and the particular cultivar. In general, the genes ARF, UBI, COX, GAP and RPL were validated as the most suitable reference gene set for every cultivar across total tested samples. Interestingly, the genes ACT and TUB, although widely used, were not the most suitable reference genes in different sweetpotato sample sets. Taken together, these results provide guidelines for reference gene(s) selection under different experimental conditions. In addition, they serve as a foundation for the more accurate and widespread use of RT-qPCR in various sweetpotato cultivars.
PMCID: PMC3520839  PMID: 23251557
3.  A NAC transcription factor and SNI1 cooperatively suppress basal pathogen resistance in Arabidopsis thaliana 
Nucleic Acids Research  2012;40(18):9182-9192.
Transcriptional repression of pathogen defense-related genes is essential for plant growth and development. Several proteins are known to be involved in the transcriptional regulation of plant defense responses. However, mechanisms by which expression of defense-related genes are regulated by repressor proteins are poorly characterized. Here, we describe the in planta function of CBNAC, a calmodulin-regulated NAC transcriptional repressor in Arabidopsis. A T-DNA insertional mutant (cbnac1) displayed enhanced resistance to a virulent strain of the bacterial pathogen Pseudomonas syringae DC3000 (PstDC3000), whereas resistance was reduced in transgenic CBNAC overexpression lines. The observed changes in disease resistance were correlated with alterations in pathogenesis-related protein 1 (PR1) gene expression. CBNAC bound directly to the PR1 promoter. SNI1 (suppressor of nonexpressor of PR genes1, inducible 1) was identified as a CBNAC-binding protein. Basal resistance to PstDC3000 and derepression of PR1 expression was greater in the cbnac1 sni1 double mutant than in either cbnac1 or sni1 mutants. SNI1 enhanced binding of CBNAC to its cognate PR1 promoter element. CBNAC and SNI1 are hypothesized to work as repressor proteins in the cooperative suppression of plant basal defense.
PMCID: PMC3467076  PMID: 22826500
4.  Tobacco seeds simultaneously over-expressing Cu/Zn-superoxide dismutase and ascorbate peroxidase display enhanced seed longevity and germination rates under stress conditions 
Journal of Experimental Botany  2010;61(9):2499-2506.
Reactive oxygen species (ROS) are produced during seed desiccation, germination, and ageing, leading to cellular damage and seed deterioration and, therefore, decreased seed longevity. The effects of simultaneous over-expression of two antioxidant enzymes on seed longevity and seed germination under stressful conditions were investigated. Transgenic tobacco simultaneously over-expressing the Cu/Zn-superoxide dismutase (CuZnSOD) and ascorbate peroxidase (APX) genes in plastids showed normal growth and seed development. Furthermore, the transgenic seeds displayed increased CuZnSOD and APX enzymatic activities during seed development and maintained antioxidant enzymatic activity after two years of dried storage at room temperature. The two-year stored non-transgenic seeds (aged NT seeds) had higher levels of ion leakage than the two-year stored transgenic seeds (aged CA seeds), indicating membrane damage caused by ROS was more severe in the aged NT seeds than the aged CA seeds. The aged CA seeds decreased germination rates as compared to newly harvested transgenic and non-transgenic seeds. The aged CA seeds, however, significantly increased germination rates under various abiotic stress conditions as compared to aged NT seeds. These data strongly suggest that simultaneous over-expression of the CuZnSOD and APX genes in plastids improves seed longevity and germination under various environmental stress conditions by attenuating the effects of oxidative stress produced by elongated storage conditions and harsh environmental stresses.
PMCID: PMC2877901  PMID: 20423937
Antioxidant enzymes; germination; seed longevity; transgenic plants

Results 1-4 (4)