Genetic and lipidomic analyses reveal the key role of lipid metabolism for cold tolerance in maize

Lipid remodeling is crucial for cold tolerance in plants.However,the precise alternations of lipidomics during cold responses remain elusive,especially in maize(Zea mays L.).In addition,the key genes responsible for cold tolerance in maize lipid metabolism have not been identified.Here,we integrate lipidomic,transcriptomic,and genetic analysis to determine the profile of lipid remodeling caused by cold stress.We find that the homeostasis of cellular lipid metabolism is essential for maintaining cold tolerance of maize.Also,we detect 210 lipid species belonging to 13 major classes,covering phospholipids,glycerides,glycolipids,and free fatty acids.Various lipid metabolites undergo specific and selective alterations in response to cold stress,especially mono-/di-unsaturated lysophosphatidic acid,lysophosphatidylcholine,phosphatidylcholine,and phosphatidylinositol,as well as polyunsaturated phosphatidic acid,monogalactosyldiacylglycerol,diacylglycerol,and triacylglycerol.In addition,we identify a subset of key enzymes,including ketoacyl-acyl-carrier protein synthase II(KAS II),acyl-carrier protein 2(ACP2),male sterility33(Ms33),and stearoyl-acyl-carrier protein desaturase 2(SAD2)involved in glycerolipid biosynthetic pathways are positive regulators of maize cold tolerance.These results reveal a comprehensive lipidomic profile during the cold response of maize and provide genetic resources for enhancing cold tolerance in crops.

The direct targets of CBFs:In cold stress response and beyond

Cold acclimation in Arabidopsis thaliana triggers a significant transcriptional reprogramming altering the expression patterns of thousands of cold-responsive(COR) genes. Essential to this process is the C-repeat binding factor(CBF)-dependent pathway, involving the activity of AP2/ERF(APETALA2/ethylene-responsive factor)-type CBF transcription factors required for plant cold acclimation. In this study, we performed chromatin immunoprecipitation assays followed by deep sequencing(ChIP-seq) to determine the genomewide binding sites of the CBF transcription factors. Cold-induced CBF proteins specifically bind to the conserved C-repeat(CRT)/dehydrationresponsive elements(CRT/DRE;G/ACCGAC) of their target genes. A Gene Ontology enrichment analysis showed that 1,012 genes are targeted by all three CBFs. Combined with a transcriptional analysis of the cbf1,2,3 triple mutant, we define 146 CBF regulons as direct CBF targets. In addition, the CBF-target genes are significantly enriched in functions associated with hormone, light,and circadian rhythm signaling, suggesting that the CBFs act as key integrators of endogenous and external environmental cues. Our findings not only define the genome-wide binding patterns of the CBFs during the early cold response, but also provide insights into the role of the CBFs in regulating multiple biological processes of plants.