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.
|
|
