Acyl-lipid desaturase 1 primes cold acclimation response in Arabidopsis.

Membrane fluidity change has long been suggested as the primary mechanism plants adapt to cold stress, but the underlying molecular mechanisms are not fully established. In this study, we found that a knockout of acyl-lipid/CoA desaturase 1 gene (ADS1; EC 1.14.99) enhances freezing tolerance after cold acclimation. Fatty acid composition analysis demonstrated that 18:1 content in ads1 mutant plants was 20% lower than WT grown at 23 °C. Lipidomics revealed that 34C- species of monogalactosyl diacylglycerol (MGDG) content in ads1 mutants were 3.3-14.9% lower than WT. Lipid positional analysis identified 10% lower 18:1 fatty acid content at the sn-2 position of MGDG. The cytosolic calcium content in ads1 mutant plants also was approximately two-times higher than that of WT in response to cold shock. Each of these biochemical differences between WT and ads1 mutant disappeared after cold acclimation. Subcellular localization of C- and N-terminal enhanced-fluorescence-fusion proteins indicated that ADS1 localized exclusively to chloroplasts. These observations suggest that ADS1-mediated alteration of chloroplast membrane fluidity is required to prime a cold acclimation response, and is the upstream event of cytosolic calcium signaling.

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