Lipidomics plays an important role in understanding plant adaptation to different stresses and improving our knowledge of the genes underlying lipid metabolism. Lipidomics involves lipid extraction, sample preparation, mass spectrometry analysis, and data interpretation. One of the practical challenges for large-scale lipidomics studies on plant leaves is the requirement of an efficient and rapid extraction method. A single-extraction method with a polar solvent mixture gives results comparable to a widely used, multi-extraction method when tested on both Arabidopsis thaliana and Sorghum bicolor leaf tissue. This single-extraction method uses a mixture of 30 parts chloroform, 25 parts isopropanol, 41.5 parts methanol, and 3.5 parts water (v/v/v/v) and a 24-h extraction time. Neither inclusion of ammonium acetate nor inclusion of acetic acid increased extraction efficiency. The extract produced by this method can be used for analysis by mass spectrometry without a solvent evaporation step. The amount of lipid extracted, including phosphatidic acid, is comparable to widely used, more labor-intensive methods. The single-extraction protocol is less laborious, reducing the potential for human error.

In response to elevated temperatures, plants alter the activities of enzymes that affect lipid composition. While it has long been known that plant leaf membrane lipids become less unsaturated in response to heat, other changes, including polygalactosylation of galactolipids, head group acylation of galactolipids, increases in phosphatidic acid and triacylglycerols, and formation of sterol glucosides and acyl sterol glucosides, have been observed more recently. In this work, by measuring lipid levels with mass spectrometry, we confirm the previously observed changes in Arabidopsis thaliana leaf lipids under three heat stress regimens. Additionally, in response to heat, increased oxidation of the fatty acyl chains of leaf galactolipids, sulfoquinovosyldiacylglycerols, and phosphatidylglycerols, and incorporation of oxidized acyl chains into acylated monogalactosyldiacylglycerols are shown. We also observed increased levels of digalactosylmonoacylglycerols and monogalactosylmonoacylglycerols. The hypothesis that a defect in sterol glycosylation would adversely affect regrowth of plants after a severe heat stress regimen was tested, but differences between wild-type and sterol glycosylation-defective plants were not detected.

Chilling temperatures (0 to 15°C) are a major constraint for temperate cultivation of tropical‐origin crops, including the cereal crop sorghum ( Sorghum bicolor [L.] Moench). Northern Chinese sorghums have adapted to early‐season chilling, but molecular mechanisms of chilling tolerance are unknown. We used RNA sequencing of seedlings to compare the chilling‐responsive transcriptomes of a chilling‐tolerant Chinese accession with a chilling‐sensitive US reference line, and mass spectrometry to compare chilling‐responsive lipidomes of four chilling‐tolerant Chinese accessions with two US reference lines. Comparative transcriptomics revealed chilling‐induced up‐regulation of cold‐response regulator C‐repeat binding factor (CBF) transcription factor and genes involved in reactive oxygen detoxification, jasmonic acid (JA) biosynthesis, and lipid remodeling phospholipase Dα1 ( PLD α 1 ) gene in the chilling‐tolerant Chinese line. Lipidomics revealed conserved chilling‐induced increases in lipid unsaturation, as well as lipid remodeling of photosynthetic membranes that is specific to chilling‐tolerant Chinese accessions. Our results point to CBF‐mediated transcriptional regulation, galactolipid and phospholipid remodeling, and JA as potential molecular mechanisms underlying chilling adaptation in Chinese sorghums. These molecular systems underlying chilling response could be targeted in molecular breeding for chilling tolerance.