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Plant height and flowering were altered in alfalfa genetically engineered to reduce lignin content.

Manipulated Organism: Alfalfa (Medicago sativa)

Inserted Transgenes: Antisense sequences of genes involved in lignin synthesis (C3H, C4H, F5H, and HCT), taken either from alfalfa or a closely related species (M. truncatula). The gene construct included the bean promoter PAL2.

Goal: Improve the digestibility of alfalfa by reducing its lignin content or altering its lignin composition. Antisense sequences were used in an attempt to suppress enzyme expression.

Intended Effect: Genetically engineered (GE) lines were created with reduced enzyme activity and lowered lignin content.

Unintended Effects:
  • Many of the GE lines were only 25-50% as tall as the parent line.

  • Flowering was delayed in the GE lines, sometimes by as much as 20 days compared with the parent line.

  • In some GE lines the flowers were white instead of their normal purple-blue color.

  • The researchers even reported a different floral scent for one of the GE lines.

Source: Reddy, M. S. S., F. Chen, G. Shadle, L. Jackson et al. (2005). "Targeted Down-regulation of Cytochrome P450 Enzymes for Forage Quality Improvement in Alfalfa (Medicago sativa L.)," Proceedings of the National Academy of Sciences vol. 102, pp. 16573-8.

Shadle, G., F. Chen, M. S. S. Reddy, L. Jackson et al. (2007). "Down-regulation of Hydroxycinnamoyl CoA: Shikimate Hydroxycinnamoyl Transferase in Transgenic Alfalfa Affects Lignification, Development and Forage Quality," Phytochemistry vol. 68, pp. 1521-9.

Author Affiliations: Samuel Roberts Noble Foundation, Ardmore, Oklahoma.

Funding: Forage Genetics International and the Samuel Roberts Noble Foundation.

Product Status: Not on the market as of April, 2009.

Copyright 2009 The Nature Institute.

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