Abstract
A culture of Cinchona ledgeriana, transformed with Agrobacterlum tumefaciens A6 capable of growing and producing quinoline alkaloids in medium free of exogenous phytohormones has been obtained. Unlike the untransformed culture of this species, addition of ZR in combination with either IAA or IBA to medium did not affect alkaloid production. Growing the transformed culture in the dark, however, produced a marked enhancement of alkaloid accumulation, up to 50 times that of cultures grown in the light. This dark-dependent accumulation was not confined to any particular time in the growth cycle, although the extent of the stimulatory effect increased the longer cultures were kept in darkness. Blue light was detrimental to alkaloid accumulation but in red or green light the level of accumulation was equivalent to that in the dark. Alternating cultures for several 28-day periods between light and dark conditions resulted in alternate periods of low and higfralkaloid productivity, indicating this was not an adaption effect. These findings correlate to previously reported differences in key enzymes from the biosynthetic pathway.
Increasing the phosphate or nitrate concentration above that of Gamborg B5, increasing sucrose above 2% (w/v), replacing sucrose with glucose or adding tryptophan or casamino acids to the medium resuited in lower alkaloid yields by dark-grown cultures of the transformed line.
