Galactolipid Synthesis in Vicia faba Leaves: I. Galactose, Glycerol, and Fatty Acid Labeling after 14CO2 Feeding 1

AUTOR(ES)

Williams, John P.

RESUMO

The galactose, glycerol, and fatty acids of mono- and digalactosyl diglycerides (MGDG and DGDG) have been separated and analyzed for 14C activity after 14CO2 feeding of Vicia faba leaf discs. Fully expanded and developing leaves were analyzed at time intervals following feeding during continuous illumination. In addition, fully expanded leaves were analyzed after similar times in complete darkness. In all cases, 14C was incorporated very rapidly into galactose, whereas glycerol and fatty acids were labeled much more slowly and over a longer period of time. The data are consistent with the galactosylation of a diglyceride to MGDG which is in turn galactosylated to DGDG. The data suggest that the formation of diglycerides suitable for galactosylation to MGDG is slow in comparison to the galactosylation process. It is also suggested that DGDG may be formed from more than one pool of MGDG. The complete analysis of the 14C incorporation into galactose appears to represent the only satisfactory method of comparing galactolipid synthesis by 14C incorporation. Estimates of comparative rates of synthesis of MGDG and DGDG have been made on this basis.

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