Effect of chilling on lipid biosynthesis in tomato pericarp disks.

摘要

Lipid biosynthesis at low temperature was studied in mature-green tomato fruits to assess its involvement in the development of chilling injury. 1-14C-acetate was incorporated at 20 and 4鳦 into pericarp discs of two cultivars differing in chilling sensitivity. At 20 and 4鳦 after 6 h pre-chilling of the fruits, free fatty acids (FFA) accounted for only 1 of the lipid label, and radioactivity was actively incorporated into diacylglycerol. In discs from 8 day pre-chilled fruits, 15-20 of the label accumulated in the FFA. At 20 and 4鳦, the label was initially high in phosphatidylcholine (PC); it decreased during the incubation while it increased in monogalactosyl-diacylglycerol (MGDG). After 8 days of chilling, this trend was more pronounced inthe sensitive cultivar Early Cherry. When discs from 6 h pre-chilled fruits were fed 14C-acetate for 72 h at 4鳦, little radioactivity was detected in 16:0 at the sn-2 position of MGDG (i.e. in prokaryotic species) in Early Cherry, while 16:0 was heavily labelled in more tolerant New York 280. One possible interpretation of the data is that biosynthesis of prokaryotic MGDG was reduced early during chilling, possibly due to inhibition of plastid glycerol-3-phosphate acyltransferase, while biosynthesisof eukaryotic MGDG was inhibited later, probably at the transfer of fatty acids from PC to MGDG.