Fragoso Selene, Espíndola Laura, Páez-Valencia Julio, Gamboa Alicia, Camacho Yolanda, Martínez-Barajas Eleazar, Coello Patricia
Departamento de Bioquímica, Facultad de Química, Universidad Nacional Autónoma de México, Mexico, Distrito Federal 04510.
Plant Physiol. 2009 Apr;149(4):1906-16. doi: 10.1104/pp.108.133298. Epub 2009 Feb 11.
During phosphate starvation, Snf1-related kinase 1 (SnRK1) activity significantly decreases compared with plants growing under normal nutritional conditions. An analysis of the expression of the genes encoding for the catalytic subunits of SnRK1 showed that these subunits were not affected by phosphate starvation. Transgenic Arabidopsis (Arabidopsis thaliana) plants overexpressing the AKIN10 and AKIN11 catalytic subunits fused with green fluorescent protein (GFP) were produced, and their localizations were mainly chloroplastic with low but detectable signals in the cytoplasm. These data were corroborated with an immunocytochemistry analysis using leaf and root sections with an anti-AKIN10/AKIN11 antibody. The SnRK1 activity in transgenic plants overexpressing AKIN11-GFP was reduced by 35% to 40% in phosphate starvation, in contrast with the results observed in plants overexpressing AKIN10-GFP, which increased the activity by 100%. No differences in activity were observed in plants growing in phosphate-sufficient conditions. Biochemical analysis of the proteins indicated that AKIN11 is specifically degraded under these limited conditions and that the increase in AKIN10-GFP activity was not due to the phosphorylation of threonine-175. These results are consistent with an important role of AKIN10 in signaling during phosphate starvation. Moreover, akin10 mutant plants were deficient in starch mobilization at night during inorganic phosphate starvation, and under this condition several genes were up-regulated and down-regulated, indicating their important roles in the control of general transcription. This finding reveals novel roles for the different catalytic subunits during phosphate starvation.
在磷饥饿期间，与在正常营养条件下生长的植物相比，蔗糖非发酵-1-相关蛋白激酶1（SnRK1）的活性显著降低。对编码SnRK1催化亚基的基因表达分析表明，这些亚基不受磷饥饿的影响。构建了过表达与绿色荧光蛋白（GFP）融合的AKIN10和AKIN11催化亚基的转基因拟南芥植株，其定位主要在叶绿体中，在细胞质中有低但可检测到的信号。使用抗AKIN10/AKIN11抗体对叶片和根切片进行免疫细胞化学分析，证实了这些数据。与过表达AKIN10-GFP的植株结果相反，过表达AKIN11-GFP的转基因植株在磷饥饿时SnRK1活性降低了35%至40%，而过表达AKIN10-GFP的植株活性增加了100%。在磷充足条件下生长的植株中未观察到活性差异。对这些蛋白的生化分析表明，AKIN11在这些有限条件下被特异性降解，并且AKIN10-GFP活性的增加不是由于苏氨酸-175的磷酸化。这些结果与AKIN10在磷饥饿信号传导中的重要作用一致。此外，在无机磷饥饿期间，akin10突变体植株在夜间淀粉动员方面存在缺陷，在此条件下几个基因上调和下调，表明它们在一般转录控制中的重要作用。这一发现揭示了不同催化亚基在磷饥饿期间的新作用。
