Enhanced vitamin C production in tomato hairy roots by precursor feeding

WEVAR OLLER AL, AGOSTINI E, MILRAD SR, MEDINA MI

Rosario

Simposio; XLII REUNIÓN ANUAL DE SAIB; 2006

SAIB

We have studied the effects of sugar precursors such us D-galactose (Gal) and D-galacturonic acid (GalUA) on ascorbic acid (AsA) production in tomato hairy roots (HR). A wild type HR clone and a transgenic UR4 HR clone were elicitated. UR4 overexpresses GalUR gene which encodes a GalUA reductase that is involved in an alternative pathway of AsA biosynthesis described in fruits. WT and UR4 were treated with 30 mM Gal and 30 mM GalUA on exponential growth phase. A detrimental effect on biomass growth and darkening of the roots was observed in both treatments 96 h post-elicitation. UR4 clone elicited with GalUA or Gal showed the highest AsA content at 168 h post-elicitation. In UR4, GalUA induced an increase of about 100% respect to UR4 controls treated with distilled sterile water, 200% respect to GalUA elicited WT HR and of 260% respect to WT HR control. On the other hand Gal induced a similar effect in WT HR, an AsA pool increase since 16 h, reaching a maximal value at 96 h post-elicitation (about 100% higher than WT HR controls treated with distilled sterile water). Our results evidence that in situ and de novo AsA biosynthesis in HR occurs via uronic acid pathways, that sugar precursors availability may be a limiting factor in AsA production in HR and that it can be enhanced (about 3-fold) by overexpression of GalUR combined with precursor feeding.