[escepticos] Patatas transgénicas

[Josep Catala <jcatala@...>]

Aprovecho el poco/nulo tráfico de mensajes, propio del
fin de semana, para haceros llegar una información que
he recibido sobre una nueva patata transgénica. Por sus
características, la novedad es realmente novedosa...

Saludos nutritivos.

Josep Català
____________Información que se cita___________

> Se adjunta esta información sobre el reciente desarrollo de
> una patata con una mejor composición de aminoacidos mediante modificación
> genética.
>
> Quisiera llamar la atención sobre unos puntos especiales de
> este nuevo OGM:
>
> - Ha sido desarrollado por un equipo de científicos indios de
> la Jawaharlal Nehru University de Nueva Delhi, que son quienes
> tienen patentado el gen.
>
> - El gen introducido procede de otra planta Amaranthus hypochondriacus
>
> - la mejora se centra en las características nutricionales
>
> Creo que rompe muchos de los tópicos existentes sobre la biotecnología.
>
>
> POTATO PACKS HIGH-PROTEIN PUNCH
>
> The production of transgenic crops containing proteins with
> improved amino acid composition should be of benefit to
> humans as well as to monogastric animals (pig, poultry, etc.),
> who are unable to synthesize all the amino acids needed to
> sustain life. The potato is the most important non-cereal food
> crop in the world; however it contains limited amounts of the
> essential amino acids lysine, tryptophan, methionine, and
> cysteine. So far, genetic engineering experiments for quality
> improvement in potato have been focused on promoting pest
> and disease resistance, increasing yield, and managing biotic
> and abiotic stresses. Efforts to improve the nutritional content of
> potato have lagged. Improvements in the nutritional value of
> food crops such as potato are especially important for people
> subsisting on a vegetarian diet in which the main source of
> protein comes from seeds, grains, tubers, etc., which contain
> limiting amounts of essential amino acids.
>
> A team of scientists from Jawaharlal Nehru University, New Delhi
> has reported improvement in the nutritive value of transgenic
> potato through the expression of a nonallergenic seed albumin
> gene (AmA1) from Amaranthus hypochondriacus. This gene,
> which was previously cloned and patented by the reporting
> team, encodes a seed-specific albumin. As a donor gene, the
> AmA1 gene has several advantages for genetic transformation
> experiments. First, this seed protein has a well-balanced amino
> acid composition, making it nutritionally superior to other
> proteins recommended by World Health Organization (WHO).
> Second, the purified protein has no known allergenic properties;
> and, finally, the protein is controlled by a single gene, which
> facilitates integration into other species.
>
> For the plant transformation experiments, potato (Solanum
> tuberosum L. var A16) shoot cultures and Agrobacterium
> tumefaciens containing AmA1 expression plasmids were used.
> To achieve expression of the introduced gene in a tuber specific
> and constitutive manner, the team used granule-bound starch
> synthase (GBSS) and cauliflower mosaic virus (CaMV) 35S
> promoters, respectively. For each transformation, 40
> independent transgenic plants were regenerated. Detection of
> the presence of the AmA1 gene in the transgenic plants by PCR
> amplification indicated the independent transformation status of
> the transgenics. Transgenic plants containing up to three
> copies of the transgene were transferred to the field and
> allowed to set tubers.
>
> The transcripts were more plentiful in tubers than stem and leaf
> tissues in the transgenic lines, evidently indicating the greater
> activity of the GBSS promoter in tubers and stolons than in
> leaves. Also there was a five- to ten-fold increase in the
> transcript level in tubers of transgenic lines containing the
> GBSS promoter (pSB8G) compared to tubers from lines in which
> the constitutive 35S promoter (pSB8) was used. However, the
> expression of AmA1 among the transgenic lines was varied
> because of position effects.
>
> The subcellular localization of AmA1 protein in both pSB8 and
> pSB8G tubers was studied to determine the basis for the
> stability of AmA1 protein in tuber cells of the transgenic plants.
> In wild type tubers, no signal for such localization was detected.
> However, AmA1 protein in transgenic plants was found to be
> present mainly in the cytoplasm and to a lesser extent in the
> vacuoles and was not accumulated into protein bodies.
>
> Amino acid analysis was carried out in five pSB8G and six pSB8
> highly expressing transgenic lines. When compared to the wild
> type A16 genotype, an increase in the essential amino acid
> content was reported in these selected transgenic lines. The
> pSB8 transgenic lines of the highly expressing tubers showed a
> significant 2.5- to 4-fold increase in lysine, methionine, cysteine,
> and tyrosine content.
>
> Experiments were carried out in a restricted experimental plot in
> which four A16 wild type potato plants, 16 independent pSB8
> transgenic lines, and eight independent pSB8G transgenic lines
> were grown. Data collected for two consecutive years showed
> consistent results. A 35 to 45% increase in total protein content
> was reported in transgenic tubers, which corresponded to an
> increase in most essential amino acids. A two-fold increase in
> tuber number and 3.0- to 3.5-fold increase in tuber yield was
> reported in both pSB8G and pSB8 lines.
>
> To test for allergenicity, mice were injected with the purified
> AMA1 protein intranasally and intraperitoneally at three
> one-week intervals. This hypersensitivity test did not evoke any
> detectable IgE response. In addition, the team could not find
> any AmA1 sequence homology to allergic proteins recorded in
> Protein Data Bank. The team reported that a literature search
> did not reveal any allergenicity associated with amaranth grain
> or forage. Grain amaranth is used in many foods throughout the
> world and amaranth forage has been used for centuries as an
> important component of the human diet throughout the tropics.
> The authors presented these facts as evidence of the
> nonallergenic nature of amaranth.
>
> The team was successful in using the seed albumin gene with a
> well-balanced amino acid composition as a donor protein to
> develop a nutritively improved transgenic potato. The study thus
> revealed the potential for biotechnological advancements to
> improve human nutrition. This knowledge will likely lead to the
> genetic modification of other crop plants with desired seed
> protein composition.
>
> Source
>
> Chakraborty S, Chakraborty N, and Datta A. 2000. Increased
> nutritive value of transgenic potato by expressing a
> nonallergenic seed albumin gene from Amaranthus
> hypochondriacus. Proceedings of the National Academy of
> Science 97(7):3724-3729. http://www.pnas.org
>
> P. Janaki Krishna
> Biotechnology Unit, Institute of Public Enterprise
> Hyderabad, India
> mailto:janakiseetha en hotmail.com