Changes in fatty acids of leaf polar lipids during chilling and post-chilling rewarming of Zea mays genotypes differing in response to chilling |
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Authors: | Zbigniew Kaniuga Violetta Sączyńska Ewa Miśkiewicz Maciej Garstka |
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Institution: | (1) Institute of Biochemistry, University of Warsaw, Al. Żwirki i Wigury 93, 02-089 Warszawa, Poland |
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Abstract: | Changes in fatty acids of leaf polar lipids: monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), sulfoquinosyldiacylglycerol
(SQDG) and phosphatidylglycerol (PG) in maize seedlings of chiling-sensitive (CS) CM 7 and Co 151 lines and chilling-tolerant
(CT) S 215 and EP 1 lines upon chilling for either 4 or 6 days in the dark and after rewarming for 4 days at original growth
conditions were studied. The content of free fatty acids (FFA) in control leaves as well as alterations in the proportion
of major fatty acids, unsaturation ratio (UR), double bond index (DBI) and changes in the proportion of heigh-temperature
melting of both phosphatidylglycerol (htm-PG) and sulfoquinovosylglycerol (htm-SQDG) after chilling and rewarming of seedlings
were estimated.
FFA content in intact leaves was 2–3-fold higher in the chilling susceptible CM 7 line than in the other three inbreeds studied.
After chilling for 6 days the level of FFA increased only in CM 7 and S 215 lines by about 30 %. Upon rewarming seedlings
chilled for 6 days the level of FFA increased about two-fold in CS Co 151 line and CT EP 1 line and decreased in CS CM 7 line.
Limited accumulation of FFAs during chilling and post-chilling rewarming of maize seedlings, did not correspond to the extent
of polar lipid breakdown (Kaniuga et al. 1999b) probably due to the contribution of active oxidative systems to the peroxidation of fatty acids under these conditions.
During rewarming seedlings chilled for 6 days major changes were observed in decrease of 18:3 and an increase of 16:0 in all
four polar lipids studied with more pronounced changes in CS than CT lines. Similarly, in CS inbreeds a decrease in UR of
fatty acids in MGDG, DGDG and SQDG after post-chilling rewarming was greater than in CT lines. Proportion of htm-fraction
in both PG and SQDG increased after post-chilling rewarming in all four inbreeds, however to a lesser extent in CT than CS
lines. A similar pattern of changes in DBI in CS and CT maize seedlings was observed in glycolipid and combine lipid classes.
More extensive degradation of polar lipids in CS than CT maize inbreeds following galactolipase action in chloroplasts (Kaniuga
et al. 1998) provides FFAs for initiation of peroxidation by LOX which is manifested by decrease of UR and DBI. This sequence of
reactions during chilling and post-chilling rewarming appears to be a main route of fatty acids peroxidation responsible for
secondary events involved in chilling injury. In addition, the extent of these changes differentiates CS and CT inbreeds.
Contribution of esterified fatty acids in thylakoid lipids to direct peroxidation, may be of minor importance. |
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Keywords: | corn Zea mays chilling response double bond index free fatty acid fatty acid composition unsaturation ratio |
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