Effects of sugar precursors and plant defense hormones on vitamin C synthesis in tomato hairy roots

AL WEVAR OLLER; E. AGOSTINI; S.R. MILRAD; M.I.MEDINA

Rosario

Simposio; XLIII REUNIÓN ANUAL DE SAIB; 2007

SAIB

Previously, we reported that in situ and de novo ascorbic acid (AsA) biosynthesis in tomato hairy roots (HR) could occur via uronic acid pathways and that AsA production can be enhanced about 3-fold by overexpression of GalUR combined with precursor feeding with D-galacturonic acid. In the present work, we used the same experimental system, consisting of a transgenic UR4 HR clone overexpressing GalUR gene which encodes a D-galacturonic acid reductase involved in an alternative pathway of AsA biosynthesis described in fruits, but we have tested other sugar precursors and also plant defense hormones. Precursor treatments consisted in addition of D-glucuronic acid, methyl D-galacturonic acid and myo-inositol at final concentration of 30 mM. Plant hormones assayed were salicylic acid (SA) and jasmonic acid (JA) at final concentration of 1 mM. All treatments were applied on exponential growth phase of HR clones. D-glucuronic and methyl D-galacturonic acid were more effective in increasing AsA content, while myoinositol has a negative effect. Regarding plant hormones treatments, SA caused a decrease in biomass and AsA production, and a change of colour in the medium; while JA induced an increment of 50% in AsA content after 48 h. Taken together, these and previous results indicate that at least two of the AsA biosynthetic pathways described so far in plants occur in the system studied.