Effect of chilling on lipid biosynthesis in tomato pericarp disks

Abstract

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°C into pericarp disks of two cultivars differing in chilling sensitivity. At 20 and 4°C 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 disks from 8 day pre-chilled fruits, 15–20% of the label accumulated in the FFA. At 20 and 4°C, the label was initially high in phosphatidylcholine (PC); it decreased during the incubation while it increased in MGDG. After 8 days of chilling, this trend was more pronounced in sensitive `Early Cherry' (EC). When disks from 6 h pre-chilled fruits were fed [ 14C]-acetate for 72 h at 4°C, little radioactivity was detected in 16:0 at the sn-2 position of MGDG (i.e. in prokaryotic species) in EC, while 16:0 was heavily labelled in more tolerant `New York 280' (NY). 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 biosynthesis of eukaryotic MGDG was inhibited later, probably at the transfer of fatty acids from PC to MGDG.