盐响应信号途径SOS与植物K^+吸收关系

Association Analysis of K^+ Uptake Features and Salt Stress Responsive Signal Pathway SOS in Arabidopsis

【目的】在盐胁迫条件下研究SOS突变体K+吸收的变化,旨在解析植物高盐胁迫响应与K+吸收的关系。【方法】以SOS信号途径的3个主要基因sos1、sos2、sos3突变体和野生型拟南芥(WT)为试验材料,在含有不同Na+/K+浓度比例的培养基上处理试验材料,观察各突变体与WT的表型差异,进行根系扫描、测定植物的RGR(相对生长率),植株体内Na+、K+的含量,计算植株体内Na+/K+浓度比值,同时,利用qRT-PCR分析K+转运体基因AKT1、AKT2、SKOR在突变体和WT间的表达差异。【结果】不同浓度K+进行处理时,突变体和WT之间没有明显差异;在30 mmol.L-1NaCl处理下,植株形态、RGR和体内Na+/K+浓度比值,体内K+浓度的测定结果显示,当K+浓度从0.2 mmol.L-1增加到60 mmol.L-1时,K+浓度增加缓解了高盐胁迫对突变体生长的抑制作用。所有植株体内的Na+/K+值降低,体内K+浓度提高。在相同处理条件下,突变体的Na+/K+值高于WT,WT体内K+浓度高于突变体;当K+浓度升高到80 mmol.L-1时,突变体的生长又重新受到抑制。所有植株体内的Na+/K+值升高,体内K+浓度降低。3个K+转运体AKT1、AKT2、SKOR的real-time PCR分析结果显示,在30 mmol.L-1NaCl处理时,在低钾条件下(0.2 mmol.L-1K+)AKT1和SKOR表达比较低,而高钾条件下(20.05 mmol.L-1K+或者60 mmol.L-1K+)AKT1、AKT2、SKOR的表达量没有明显差异,这3个基因的表达方式在突变体之间没有明显的差异。【结论】在中度盐胁迫条件下,外界K+浓度增加可以缓解盐胁迫对植物生长造成的抑制作用,但是当外界一价阳离子的总浓度高于110 mmol.L-1时,拟南芥的生长重新受到抑制。SOS信号途径对植物K+吸收没有直接的调节作用。

【Objective】 To clarify the relationship between salt stress response and K^＋ uptake in plants, dynamic change of K^＋ uptake in SOS mutants under salt stress was investigated by using three Arabidopsis mutants of sos1, sos2, and sos3 involved in the SOS signal pathway as materials.【Method】 The Arabidopsis mutants materials plus the wild type （WT） were treated on MS medium containing various concentration ratios of Na^＋/K^＋, then their phenotypes in plant appearances were observed and analyzed by comparison. Also their roots scanning, RGR （relative growth rate）, Na^＋, and K^＋ content, and Na^＋/K^＋ ratio in vivo were tested. Furthermore, the expression difference of K^＋ transporter genes such as AKT1, AKT2 and SKOR between the materials was identified by qRT-PCR. 【Result】No significant difference was found in the above explored traits between the mutants and WT when they were cultured on the MS medium with different concentrations of K^＋. In the treatment of 30 mmol·L^-1 NaCl and the range of 0.2-60 mmol·L^-1 K^＋, the increase of K^＋ concentration alleviated the growth inhibition of the mutants caused by high salt stress, and reduced the Na^＋/K^＋ ratio and enhanced the K^＋ concentration in vivo in all materials. Under a fixed treatment, Na^＋/K^＋ ratio was higher in the mutants than in WT, but K^＋ concentration was higher in WT than in the mutants. However, when K^＋ up to 80 mmol·L^-1 in medium the growth of the mutants was inhibited again, and at the same time Na^＋/K^＋ ratio increased and K^＋ decreased in vivo of all plants. Real-time PCR analysis showed that the expression of AKT1 and SKOR was relatively low under the condition of 30 mmol·L^-1 NaCl and low concentration potassium （0.2 mmol·L^-1 K^＋）. Under 30 mmol·L^-1 NaCl and high concentration potassium （20.05 mmol·L^-1 K^＋ or 60 mmol·L^-1 K^＋）, the expressions of AKT1, AKT2 and SKOR appeared no significant difference and their expression patterns were almost similar in different mutants. 【Conclusion】 Under moderate salt stress conditions, growth suppression of the plants caused by the salt stress could be alleviated with the increase of K^＋ concentration. But, when the concentration of external univalence cation was over 110 mmol·L^-1, the growth status of the plants was restrained again. Therefore, it was speculated that SOS signaling pathway was not involved in the regulation of absorption and transport of K^＋ directly.