Knock-Down of the Phosphoserine Phosphatase Gene Effects Rather N- Than S-Metabolism in Arabidopsis thaliana
Knock-Down of the Phosphoserine Phosphatase Gene Effects Rather N- Than S-Metabolism in Arabidopsis thaliana
复制标题
DOI：
10.3389/fpls.2018.01830
复制
发表时间：
2018-12-11
影响因子：
5.6
通讯作者：
Rennenberg, Heinz
中科院分区：
文献类型：
--
作者：
Samuilov, Sladjana;Rademacher, Nadine;Rennenberg, Heinz
本研究的目的是阐明磷酸化途径的丝氨酸生产的半胱氨酸生物合成在昼夜和镉（Cd）暴露后的意义。为此，使用拟南芥野生型植物作为对照和其磷酸丝氨酸磷酸酶（PSP）敲低的psp突变体来测试（i）光呼吸Ser是否是光下自养组织中Cys合成的主导前体，（ii）Ser产生的磷酸化途径是否可以在夜间接管叶片中Ser的生物合成，镉暴露刺激半胱氨酸和谷胱甘肽（GSH）的生物合成和影响串扰的S和N代谢，无论丝氨酸来源。甘氨酸（Gly）和丝氨酸含量不受影响的psp转录水平的减少，证实光呼吸途径是主要途径的丝氨酸合成。突变体中PSP转录水平的降低并不影响硫通量的昼夜调节，而不再观察到硫代谢物量的昼夜波动，这可能是由于突变体中硫代谢物的周转较慢。镉处理后，在两种基因型和GSH的非蛋白巯基的含量增加，只有在PSP突变体观察。丝氨酸磷酸化途径的突变导致丙氨酸、天冬氨酸、赖氨酸的积累和支链氨基酸的减少。PSP基因的敲除诱导了与野生型植物不同的针对镉毒性的额外防御机制。
The aim of present study was to elucidate the significance of the phosphorylated pathway of Ser production for Cys biosynthesis in leaves at day and night and upon cadmium (Cd) exposure. For this purpose, Arabidopsis wildtype plants as control and its psp mutant knocked-down in phosphoserine phosphatase (PSP) were used to test if (i) photorespiratory Ser is the dominant precursor of Cys synthesis in autotrophic tissue in the light, (ii) the phosphorylated pathway of Ser production can take over Ser biosynthesis in leaves at night, and (iii) Cd exposure stimulates Cys and glutathione (GSH) biosynthesis and effects the crosstalk of S and N metabolism, irrespective of the Ser source. Glycine (Gly) and Ser contents were not affected by reduction of the psp transcript level confirming that the photorespiratory pathway is the main route of Ser synthesis. The reduction of the PSP transcript level in the mutant did not affect day/night regulation of sulfur fluxes while day/night fluctuation of sulfur metabolite amounts were no longer observed, presumably due to slower turnover of sulfur metabolites in the mutant. Enhanced contents of non-protein thiols in both genotypes and of GSH only in the psp mutant were observed upon Cd treatment. Mutation of the phosphorylated pathway of Ser biosynthesis caused an accumulation of alanine, aspartate, lysine and a decrease of branched-chain amino acids. Knock-down of the PSP gene induced additional defense mechanisms against Cd toxicity that differ from those of WT plants.