GDP-D-mannose 3,5-epimerase (GME) plays a key role at the intersection of ascorbate and non-cellulosic cell-wall biosynthesis in tomato.
Plant J
; 60(3): 499-508, 2009 Nov.
Article
en En
| MEDLINE
| ID: mdl-19619161
The GDP-D-mannose 3,5-epimerase (GME, EC 5.1.3.18), which converts GDP-d-mannose to GDP-l-galactose, is generally considered to be a central enzyme of the major ascorbate biosynthesis pathway in higher plants, but experimental evidence for its role in planta is lacking. Using transgenic tomato lines that were RNAi-silenced for GME, we confirmed that GME does indeed play a key role in the regulation of ascorbate biosynthesis in plants. In addition, the transgenic tomato lines exhibited growth defects affecting both cell division and cell expansion. A further remarkable feature of the transgenic plants was their fragility and loss of fruit firmness. Analysis of the cell-wall composition of leaves and developing fruit revealed that the cell-wall monosaccharide content was altered in the transgenic lines, especially those directly linked to GME activity, such as mannose and galactose. In agreement with this, immunocytochemical analyses showed an increase of mannan labelling in stem and fruit walls and of rhamnogalacturonan labelling in the stem alone. The results of MALDI-TOF fingerprinting of mannanase cleavage products of the cell wall suggested synthesis of specific mannan structures with modified degrees of substitution by acetate in the transgenic lines. When considered together, these findings indicate an intimate linkage between ascorbate and non-cellulosic cell-wall polysaccharide biosynthesis in plants, a fact that helps to explain the common factors in seemingly unrelated traits such as fruit firmness and ascorbate content.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Ácido Ascórbico
/
Carbohidrato Epimerasas
/
Pared Celular
/
Solanum lycopersicum
Idioma:
En
Revista:
Plant J
Asunto de la revista:
BIOLOGIA MOLECULAR
/
BOTANICA
Año:
2009
Tipo del documento:
Article
País de afiliación:
Francia
Pais de publicación:
Reino Unido