ENHANCED ANTHOCYANIN PRODUCTION IN GRAPE CELL-CULTURES

Cultured grape cells (Bailey Alicant A Vitis hybrid) that produce and accumulate anthocyanins provide a convenient model system to study secondary metabolite formation and compartmentation. A reduction in anthocyanin production in suspension cultures occurred after a series of subcultures in liquid Gamborg's B5 (GB5) maintenance medium. In contrast, newly derived suspensions from selected red calluses retained their ability to produce anthocyanin at a sustained high level. A production medium with reduced nitrate and elevated sucrose induced very high levels of anthocyanin (up to 2.9 g/l) in suspension cultures derived from selected callus. This medium also induced increased pigment production in faded suspension cultures and in callus cultures of Vignoles [Ravat 51, Vitis hybrid] which normally do not produce anthocyanin in culture. Reduction of nitrate to a critical level resulted in a 'switchlike' (rather than gradual) enhancement of anthocyanin production which may represent the removal of an inhibitory effect. Improvements obtained with sucrose were probably due to increased medium osmolarity. The combined effects of low nitrate and high sucrose synergistically improved anthocyanin volumetric productivity (up to 0.15 g/l. day) and surpassed previously published values for cultured grape cells. Our results indicate a possible involvement of a nitrate-sensitive tonoplast ATPase in the accumulation of anthocyanin in grape vacuoles.