High Day and Night Temperatures Result in Major Lipid Alterations in Wheat and Co-Occurring Lipids Represent Groups That Are Explained By Coordinated Metabolism.

Understanding how wheat plants under high temperature regulate lipid composition is critical to developing climate-resilient wheat varieties. We measured 165 glycerolipids and sterol derivatives under optimum and high day and night temperatures in leaves of two wheat genotypes using electrospray ionization-tandem mass spectrometry. Levels of polar lipid fatty acyl chain unsaturation were lower under high temperatures, compared to optimum temperature. The lower unsaturation was predominantly due to lower levels of 18:3 and higher levels of 18:1 and 16:0 acyl chains. Levels of 18:3-containing triacylglycerols increased 3-fold/more under high temperatures, consistent with their possible role in sequestering fatty acids during membrane lipid remodeling. Phospholipids containing odd-numbered or oxidized acyl chains accumulated in leaves under high temperatures. Sterol glycosides and 16:0-acylated sterol glycosides were higher under high temperatures than optimum temperature. Correlation analysis of lipid levels revealed 13 groups of co-occuring lipids, which are up-or-down-regulated together through time during high temperature stress. Current knowledge of lipid metabolism suggests that the lipids in each group co-occur because they are regulated by the same enzyme(s). Taken together, the data demonstrate that wheat leaf lipid composition is altered by high day and night temperature stress, that some lipids are particularly responsive to high temperatures, and co-occurring lipids represent groups that can be explained by coordinated metabolism.