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Alfalfa with corn transgenes for anthocyanin (red-purple pigment) production was not visibly altered or changed dependent on light and temperature conditions.

Manipulated Organism: Alfalfa (Medicago sativa).

Inserted Transgenes: Three transgenic lines of alfalfa were produced by introducing either Lc, B-Peru, or C1. All three genes are anthocyanin regulatory genes from maize (Zea mays). In maize, Lc (leaf color) induces the expression of enzymes that form red anthocyanin pigments in several plant tissues. Lc was fused to the cauliflower mosaic virus (CaMV-35S) promoter so that the gene was expressed in all parts of the plant.

Goal: Produce transgenic alfalfa with higher contents of anthocyanins and proanthocyanidins in stems and leaves. Increased amounts of these substances are meant to improve feed quality by preventing pasture bloat in ruminant livestock and increasing the efficiency of conversion of plant protein into animal protein.

Intended Effect: Transgenic Lc alfalfa synthesizes anthocyanins and proanthocyanidins in natural sunlight and under greenhouse conditions when subjected to high light intensity or cold.

Unintended Effects:
  • Grown in moderate greenhouse conditions, Lc plants expressed abundant transcripts of the transgene in their leaves. However, no anthocyanins or proanthocyanidins accumulated under these conditions and the transgenic plants were bright green.
  • Microscopically, there were more air spaces between cells.
  • Red color was visibly induced within hours in most Lc plants when they were subjected to bright light or low temperatures, and within three days the plants changed completely in color. The red color faded quickly when these conditions were removed.
  • The flavone content in the leaves and stems of the Lc plants was reduced. Flavones in the animal and human diet may reduce the risk of some diseases (cancer, cardiovascular disease).
  • B-Peru transgenic and C1 transgenic alfalfa populations showed no visible accumulation of the desired pigments, although the inserted transgenes were expressed at detectable levels.

Additional Comments: This study shows that anthocyanin production is "a function of environmental conditions and transgene specificity" (p. 1456); in other words it is highly context-dependent.

Source: Ray, H., M. Yu, P. Auser, L. Blahut-Beatty et al. (2003). "Expression of Anthocyanins and Proanthocyanidins after Transformation of Alfalfa with Maize Lc," Plant Physiology vol. 132, pp. 1448-63.

Author Affiliations: Saskatoon Research Centre, Agriculture and Agri-Food Canada; Plant Biotechnology Institute, Saskatoon, Saskatchewan; University of Guelph, Ontario; University of Texas, Austin.

Funding: Supported in part by grants from the Alberta Agriculture Research Institute, the Alberta Cattle Commission, and the Saskatchewan Agricultural Development Fund.

Product Status: Not on the market as of 2008.

Copyright 2008 The Nature Institute.

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