Phospholipid Acyl Chain and Phospholipase Dynamics during Cold Acclimation of Winter Wheat

Abstract

on the phospholipid profiles. It has been suggested that alterations in concentration of specific phospholipids Phospholipid (PL) composition is known to change in plants explay a role in cold acclimation. Horvath et al. (1979) posed to cold temperature. The dynamics of PL acyl chain pairs and genes encoding phospholipase enzymes were studied in winter wheat observed an inverse relationship between survival and (Triticum aestivum L.) during cold acclimation. Mass spectrometry the loss of phosphatidylcholine by conversion to the corwas used to characterize PL dynamics, and quantitative real-time responding phosphatidic acid in field-grown wheat PCR was used to characterize phospholipase gene mRNA transcript plants. A similar conversion of phosphatidylcholine to dynamics during cold acclimation. The proportion of PLs with misphosphatidic acid was reported by De La Roche and matched acyl chains decreased concomitantly with an increase in total Andrews (1973) in plants grown at 2ЊC and morphologi-PLs during the first week of cold exposure. Proportions of mismatched cally equivalent plants grown at 24ЊC, again suggesting acyl chains then increased, while total PLs varied little. Numbers of these phospholipid dynamics are a function of plant phe-mRNA transcripts of phospholipase (PL)D, PLC, and PLA 2 increased nology rather than cold acclimation. in response to cold and remained at elevated levels throughout a 4-wk The proportion of unsaturated fatty acids, particularly period. Lysophosphatidylcholine (LPC) increased as much as 14-fold over the 5-wk period and increased significantly less in a less cold linolenic acid (18 carbons, three double bonds [18:3]), tolerant cultivar than more tolerant cultivars. It appeared that newly 209 Johnson Hall, Washington State Univ., Pullman, WA 99164; S. Halls and W.F. Siems,

Carbohydrate and Lipid Dynamics in Wheat Crown Tissue in Response to Mild Freeze–Thaw Treatments

“…1) were consistent with the observations that initial exposure to subzero temperature results in depolymerization of fructan (Livingston and Henson, 1998), and that elevated levels of sucrose induce fructan synthesis (De Roover et al, 2000;Maleux and Van den Ende, 2007), as we observed in the -3,48 h treatment (Fig. We previously demonstrated that the expression levels of some genes encoding phospholipases (Skinner et al, 2005) and phospholipase A 2 enzyme activity (Skinner, 2009a) in wheat crown tissue rapidly increased when the plants were transferred to a cold acclimation-inducing temperature, remained elevated as the plants continued to acclimate and develop greater freezing tolerance, then declined as the acclimation process was completed and the freezing tolerance of the plants began to decline. As these changes in concentrations of sugars were occurring, characteristic changes in lipid species also were occurring.…”

“…3). Fatty acids of 12 to 16 carbons are very common acyl sidechains of phospholipids in wheat cell membranes (Skinner et al, 2005); hence, this result is consistent with the observation that small lipids, including free fatty acids derived response to the onset of subfreezing temperature, but that response was transient and largely, but not entirely, dissipated within 48 h, regardless of whether the subfreezing temperature stress was removed or remained constant. 3), suggesting the -3°C, 24 h treatment resulted in the generation of several lipid species in that size range.…”

“…By the end of about 5 wk of cold acclimation, the plants have reached essentially the greatest level of freezing tolerance they will attain at low, above-freezing temperature (Vagujfalvi et al, 1999), and the ratio of unequal:equal phospholipid acyl chain lengths has returned to nearly preacclimation levels (Skinner et al, 2005). By the end of about 5 wk of cold acclimation, the plants have reached essentially the greatest level of freezing tolerance they will attain at low, above-freezing temperature (Vagujfalvi et al, 1999), and the ratio of unequal:equal phospholipid acyl chain lengths has returned to nearly preacclimation levels (Skinner et al, 2005).…”

Evidence of a major genetic factor conditioning freezing sensitivity in winter wheat

“…2005). We previously demonstrated that exposure of ORFW to 4°C resulted in changes of phospholipid profiles that were similar to changes in ‘Eltan’, ‘Froid’, ‘Kestrel’ and ‘Tiber’, over a 5‐week period of acclimation (Skinner et al. 2005).…”

“…Also, given the observation of ‘different genetic mechanisms controlling cold resistance at each temperature level’ (Parodi 1969), the identification of specific genes will require evaluation of inheritance of freezing tolerance at defined temperatures. Winter wheat line ‘Oregon Feed Wheat #5’ (ORFW) was reported to have very little freezing tolerance in controlled temperature studies (Skinner et al. 2005), and in the field (DeNoma 1990).…”