Molecular mechanism of acclimation and tolerance to low temperature.

(1)不饱和膜脂对耐寒性和抗冻性的影响：直到最近一年，我们证明了不饱和膜脂通过促进光抑制光系统的修复来保护植物和蓝藻的光合作用机制，使其免受低温下的光抑制。此外，它们在光合作用机制对盐胁迫的耐受性中也是重要的。(2)甜菜碱对寒冷和冷冻胁迫的保护：我们以前证明了使拟南芥合成甘氨酸甜菜碱的基因操作提高了对生活周期不同阶段各种环境胁迫的耐受性。在这一年里，我们阐明了甜菜碱的保护作用是基于通过稳定蛋白质合成机制促进蛋白质从头合成。(3)冷驯化新因素：利用DNA微阵列对集胞藻中冷诱导基因的表达进行全局检测，发现冷胁迫诱导了一系列基因，这些基因编码转录和翻译因子、核糖体的亚单位蛋白、RNA解旋酶以及一些功能未知的蛋白质。这些蛋白质在冷驯化中的功能是未来研究的重要课题。(4)冷感受器和冷信号转导途径：截至去年，我们鉴定了两个冷感受器和一个冷信号转导。在这一年里，我们应用DNA微阵列，根据冷传感器对冷诱导的调控，成功地将冷诱导基因分为三类。第一组基因受第一个冷传感器调控，第二组基因受第二个传感器调控，第三组基因受两个传感器调控。

(1) The effect of unsaturated membrane lipids on tolerance to cold and freezing stress : Up to the last year we demonstrated that unsaturated membrane lipids protect the photosynthetic machinery of plants and cyanobacteria against the photoinhibition at low temperature by promoting the repair of photoinhibited photosystem II.In this year, we have elucidated that the unsaturated membrane lipids accelerate the translation of psbA gene for the precursor to D1 protein, and furthermore that they are also important in the tolerance of the photosynthetic machinery to salt stress.(2) Protection against cold and freezing stress by glycinebetaine : We previously demonstrated that the genetic manipulation to enable Arabidopsis to synthesize glycinebetaine enhances tolerance to various kinds of environmental stress at various stages of life cycle. In this year we have elucidated that the protective effect of glycinebetaine is based on the promotion of protein synthesis de novo by stabilizing the protein-synthesizing machinery.(3) New factors for cold acclimation : The global examination of cold-inducible expression of genes in Synechocystis with DNA microarrays has revealed that cold stress induces a number of genes, which encode factors in transcription and translation, subunit proteins of ribosomes, RNA helicases, and a number of proteins of unknown function. Functions of these proteins in cold acclimation are important subjects of future study.(4) Cold sensor and cold signal transduction pathway : Up to the last year, we identified two cold sensors and a cold-signal transducer. In this year, we have applied DNA microarrays to successfully classify cold-inducible genes into three groups according to the regulation of cold inducibility by the cold sensors. Group-1 genes are regulated by the first cold sensor, Group-2 genes are by the second sensor, and Group-3 genes are by both sensors.