Browsing by Author "Medina, C."

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    Cisgenesis and Intragenesis: New tools For Improving Crops
    (2013) Espinoza, C.; Schlechter, R.; Herrera, D.; Torres, E.; Serrano, A.; Medina, C.; Arce-Johnson, P.
    Genetically Modified Organisms (GMO) could be the answer for many relevant problems affecting crops. However, improving crops through GMO is also often associated with safety concerns, environmental risks and health issues due to the presence of foreign DNA. These limitations have prompted the development of alternative technologies. Recently, cisgenesis and intragenesis have been developed as new tools aimed to modify crops. While cisgenesis involves genetic modification using a complete copy of natural genes with their regulatory elements that belong exclusively to sexually compatible plants, intragenesis refers to the transference of new combinations of genes and regulatory sequences belonging to that particular species. So far, application of cisgenesis and intragenesis as alternatives to conventional transgenesis are limited to a few species, mainly due to the lack of knowledge of the regulatory sequences required. The grape is one of the most cultivated crops worldwide and is the most economically relevant crop in Chile. Its genomic sequence has been completed, making available new sources of information to improve grape traits by genetic manipulation. This review is focused on the current alternatives to transgenesis in plants, including new approaches to develop marker-free crops, their application to economically relevant crops and future perspectives in the area. Also, the identification of grapevine promoters with a wide range of expression profiles is shown. The expression pattern of these genes was analyzed in different tissues and developmental stages, as well as under several stresses and stimuli, giving a broad range of expression patterns, including genes expressed exclusively during ripening, in response to sugars, senescence and biotic stress, among others. Genes with strong and constitutive expression were also identified. Functional analysis using reporter genes has been conducted in order to confirm the promoter's transcription activity, opening new possibilities for developing cisgenic/intragenic grapevines.
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    Senescence-associated genes induced during compatible viral interactions with grapevine and Arabidopsis
    (2007) Espinoza, C.; Medina, C.; Somerville, S.; Arce-Johnson, P.
    The senescence process is the last stage in leaf development and is characterized by dramatic changes in cellular metabolism and the degeneration of cellular structures. Several reports of senescence-associated genes (SAGs) have appeared, and an overlap in some of the genes induced during senescence and pathogen infections has been observed. For example, the enhanced expression of SAGs in response to diseases caused by fungi, bacteria, and viruses that trigger the hypersensitive response (HR) or during infections induced by virulent fungi and bacteria that elicit necrotic symptoms has been observed. The present work broadens the search for SAGs induced during compatible viral interactions with both the model plant Arabidopsis thaliana and a commercially important grapevine cultivar. The transcript profiles of Arabidopsis ecotype Uk-4 infected with tobacco mosaic virus strain Cg (TMV-Cg) and Vitis vinifera cv. Carmenere infected with grapevine leafroll-associated virus strain 3 (GLRaV-3) were analysed using microarray slides of the reference species Arabidopsis. A large number of SAGs exhibited altered expression during these two compatible interactions. Among the SAGs were genes that encode proteins such as proteases, lipases, proteins involved in the mobilization of nutrients and minerals, transporters, transcription factors, proteins related to translation and antioxidant enzymes, among others. Thus, part of the plant's response to virus infection appears to be the activation of the senescence programme. Finally, it was demonstrated that several virus-induced genes are also expressed at elevated levels during natural senescence in healthy plants.