Phosphatidylglycerol and Chilling Sensitivity in Plants

Abstract

The hypothesis that molecular species of thylakoid phosphatidylglycerol containing 2 saturated fatty acids (disaturated phosphatidylglycerol) confer chilling sensitivity upon plants was tested by analyzing the fatty acid composition of phosphatidylglycerols isolated from leaves of a range of plants expected to have different sensitivities to chilling temperatures. Saturated fatty acids (palmitate plus stearate plus hexadeca-trans-3-enoate) as a proportion of total phosphatidylglycerol fatty acids varied from 51-80 mol percent in the plants analyzed but appeared to be rigidly fixed for a given plant species, being unaffected by leaf maturity or by environment. Hexadeca-trans-3-enoate occurred only at the sn-2 position, whereas C-18 fatty acids occurred only at the sn-1 position of thylakoid phosphatidylglycerol. The proportion of disaturated molecular species could be predicted accurately from the total fatty acids of phosphatidylglycerol. Disaturated molecular species accounted for < 25% of the total phosphatidylglycerol from leaves of chilling-resistant plants and for 50-60% of the phosphatidylglycerol in leaves from some of the most chilling-sensitive plants. Not all chilling-sensitive plants contained high proportions of disaturated phosphatidylglycerol; solanaceous and other 16:3-plants and C4 grasses may be important exceptions. Proportions of disaturated phosphatidylglycerol increased concomitantly with increasing chilling sensitivity of plants within a genus.