Resarch of metabolic responses to environmental stress in halophyte and regulation by protein kinase

甜菜碱作为一种亲和性溶质在某些植物体内大量积累，被认为具有保护植物免受盐胁迫的作用。甜菜碱积累植物的甜菜碱生物合成途径包括以胆碱单加氧酶（CMO）为关键酶和磷酸乙醇胺n -甲基转移酶（PEAMT），它们需要s -腺苷- l-蛋氨酸（SAM）作为甲基供体。SAM是由SAM合成酶（SAMS）合成的，不仅用于甜菜碱的合成，也用于其他化合物的合成，尤其是木质素。从一株藜属盐生植物中克隆了CMO、PEAMT和SAMS等基因。甜菜碱在叶片和茎中的转录本和蛋白水平均高于根，表明甜菜碱主要在茎部合成。SAMS和PEAMT转录本在盐胁迫缓解期间和之后的调控模式与CMO在叶片中的调控模式高度相似，且具有昼夜节律性。盐胁迫对甜菜碱含量的影响较大，但对木质素含量的影响不大。这些结果表明，SAMS的转录水平与PEAMT和CMO的转录水平协同调节，为甜菜碱在叶片中的合成提供SAM。我们构建了一系列拟南芥MAPK激酶（AtMEKK1）的缺失突变体，获得了一个组成型活性突变体AtMEKK1 Δ166，该突变体缺乏n端166个氨基酸的自抑制序列，但仍具有底物特异性。AtMEKK1 Δ166主要磷酸化拟南芥MAPKK AtMEK1，但不磷酸化其双突变体（AtMEK1T218A/S224E），表明Thr-218和Ser-224是磷酸化位点。在受伤的幼苗中，AtMEKK1被激活并磷酸化其下游的AtMEK1。此外，使用抗atmekk1和抗atmek1抗体进行分析显示，这两种蛋白之间的相互作用是信号依赖性的。这些结果表明AtMEKK1-AtMEK1通路的存在是由损伤诱导的。考虑到我们之前的数据支持AtMEK1-ATMPK4通路，我们在这里提供了新的数据来完成在拟南芥幼苗损伤下工作的AtMEKK1-AtMEK1-AtMPK4级联。少

Glycinebetaine (betaine) highly accumulates as a compatible solute in certain plants and has been considered to play a role in the protection from salt stress. The betaine biosynthesis pathway of betaine-accumulating plants involves choline monooxygenase (CMO) as the key enzyme and phosphoethanolamine N-methyltransferase (PEAMT), which require S-adenosyl-L-methionine (SAM) as a methyl donor. SAM is synthesized by SAM synthetase (SAMS), and is needed not only for betaine synthesis but also for the synthesis of other compounds, especially lignin. We cloned CMO, PEAMT and SAMS isogenes from a halophyte Atriplex nummularia L. (Chenopodiaceous). The transcript and protein levels of CMO were much higher in leaves and stems than in roots, suggesting that betaine is synthesized mainly in the shoot. The regulation patterns of transcripts for SAMS and PEAMT highly resembled that of CMO in the leaves during and after relief from salt stress, and on a diurnal rhythm. In the leaves, the betaine con … More tent was increased but the lignin content was not changed by salt stress. These results suggest that the transcript levels of SAMS are coregulated with those of PEAMT and CMO to supply SAM for betaine synthesis in the leaves.We have constructed a series of deletion mutants of Arabidopsis MAPK kinase kinase (AtMEKK1) and obtained a constitutively active mutant, AtMEKK1 Δ166, which lacks in self-inhibitory sequence of N-terminal 166 amino acids but still has substrate specificity. AtMEKK1 Δ166 predominantly phosphorylates AtMEK1, an Arabidopsis MAPKK, but not its double mutant (AtMEK1T218A/S224E), suggesting that Thr-218 and Ser-224 are the phosphorylation sites.In wounded seedlings, AtMEKK1 was activated and phosphorylated its downstream AtMEK1. Furthermore, analysis using anti-AtMEKK1 and anti-AtMEK1 antibodies revealed that the interaction between the two proteins was signal dependent. These results suggest the presence of AtMEKK1-AtMEK1 pathway induced by wounding. Taking account of our previous data supporting the AtMEK1-ATMPK4 pathway, we provide here new data to complete the AtMEKK1-AtMEK1-AtMPK4 cascade that works under wounding of Arabidopsis seedling. Less