Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
Planta. 2010 Jun;232(1):37-49. doi: 10.1007/s00425-010-1150-9. Epub 2010 Apr 1.
Tuber formation in potato (Solanum tuberosum L.) is regulated by hormonal and environmental signals that are thought to be integrated in the leaves. The molecular mechanisms that mediate the responses to tuberization-related signals in leaves remain largely unknown. In this study we analyzed the roles of protein phosphatase type 2A catalytic subunits (PP2Ac) in the leaf responses to conditions that affect tuberization. The responses were monitored by analyzing the expression of the "tuber-specific" genes Patatin and Pin2, which are induced in tubers and leaves during tuber induction. Experiments using PP2A inhibitors, together with PP2Ac expression profiles under conditions that affect tuberization indicate that high sucrose/nitrogen ratio, which promotes tuber formation, increases the transcript levels of Patatin and Pin2, by increasing the activity of PP2As without affecting PP2Ac mRNA or protein levels. Gibberellic acid (GA), a negative regulator of tuberization, down-regulates the transcription of catalytic subunits of PP2As from the subfamily I and decreases their enzyme levels. In addition, GA inhibits the expression of Patatin and Pin2 possibly by a PP2A-independent mechanism. PP2Ac down-regulation by GA may inhibit tuberization signaling downstream of the inductive effects of high sucrose/nitrogen ratio. These results are consistent with the hypothesis that PP2As of the subfamily I may positively modulate the signaling pathways that lead to the transcriptional activation of "tuber-specific" genes in leaves, and act as molecular switches regulated by both positive and negative modulators of tuberization.
马铃薯（Solanum tuberosum L.）的块茎形成受激素和环境信号的调节，这些信号被认为在叶片中整合。介导与块茎形成相关的信号在叶片中的响应的分子机制在很大程度上仍然未知。在这项研究中，我们分析了蛋白磷酸酶 2A 催化亚基（PP2Ac）在叶片对影响块茎形成的条件的响应中的作用。通过分析“块茎特异性”基因 Patatin 和 Pin2 的表达来监测响应，这两个基因在块茎和叶片中在块茎诱导期间被诱导。使用 PP2A 抑制剂的实验，以及在影响块茎形成的条件下 PP2Ac 表达谱的实验表明，高蔗糖/氮比（促进块茎形成）通过增加 PP2As 的活性而不影响 PP2Ac mRNA 或蛋白质水平来增加 Patatin 和 Pin2 的转录物水平。赤霉素（GA）是块茎形成的负调节剂，下调 I 亚家族的 PP2A 催化亚基的转录，并降低其酶水平。此外，GA 可能通过非 PP2A 机制抑制 Patatin 和 Pin2 的表达。GA 下调 PP2Ac 可能会抑制高蔗糖/氮比诱导作用下游的块茎形成信号。这些结果与以下假设一致：I 亚家族的 PP2As 可能正向调节导致叶片中“块茎特异性”基因转录激活的信号通路，并作为受块茎形成的正调节剂和负调节剂调节的分子开关。
