Lipid composition and turnover in heterotrophic cell suspension cultures of Saccharum officinarum

Utilizing radioactively labelled precursors we found that fully heterotrophic sugarcane cells without carotenoids and chlorophyll and absolutely dependent on sucrose for growth were capable of incorporating galactose into both mono- and di-galactosyldiacylglycerol (MGDG and DGDG), sulfate and galactose into sulfolipid (SL), and phosphate into phosphatidylglycerol (PG). All above-mentioned lipids showed turnover allowing the calculation of their half-lifes: τ_0.5 = 28 h for MGDG. There is an initial increment in the labelling of DGDG (at the expense of MGDG) and then a decrement with τ_0.5 = 27 h. The SL shows a τ_0.5 = 30 h and τ_0.5 = 28 h for PG. It is evident that during differentiation changes in lipid metabolism occur allowing the cell not only to increase, but to localize preferentially the biosynthetic machinery of the above-mentioned lipids in the chloroplasts and to make the process light-dependent.