Sugar metabolism of Vetiveria zizanioides cells cultured with Amberlite XAD-4: uptake of radiolabelled sugars, cell wall invertase activity and gene expression

Activated and non-activated Amberlite XAD-4 was added to the cell cultures of vetiver (Vetiveria zizanioides Stapf.) in order to study its effects as abiotic growth promoter. Amberlite XAD-4 increased vetiver cell viability, especially when used in the activated form. Results from labelling experiments in cell suspensions showed that XAD-4 prompted a significant decrease of sucrose Km, accompanied by an increased Vmax. Glucose uptake from the medium was almost doubled, as demonstrated by the increase of the radiolabelled fraction (25-fold the controls) in vetiver cells cultured with XAD-4. Affinity for fructose uptake by cells was not altered by the use of activated XAD-4, even though its uptake and Vmax increased. These results were further supported by a significant 7.5-fold increase in cell wall invertases (CWI) activity in XAD-4 elicited cells. Vetiver CWI gene expression was characterized by transcript RT-PCR analysis. The identity of the transcripts was confirmed by sequencing analysis. These results indicated the use of XAD-4 as an effective tool for vetiver cell biomass optimisation.