Bradai Mariem, Mahjoubi Habib, Chini Andrea, Chabouté Marie-Edith, Hanin Moez, Ebel Chantal
Laboratory of Biotechnology and Plant Improvement, Center of Biotechnology of Sfax, Sfax, Tunisia.
Institut de Biologie Moléculaire des Plantes, CNRS, Université de Strasbourg, Strasbourg, France.
PLoS One. 2018 Jan 16;13(1):e0191272. doi: 10.1371/journal.pone.0191272. eCollection 2018.
Reversible phosphorylation is an essential mechanism regulating signal transduction during development and environmental stress responses. An important number of dephosphorylation events in the cell are catalyzed by type one protein phosphatases (PP1), which catalytic activity is driven by the binding of regulatory proteins that control their substrate specificity or subcellular localization. Plants harbor several PP1 isoforms accounting for large functional redundancies. While animal PP1s were reported to play relevant roles in controlling multiple cellular processes, plant orthologs remain poorly studied. To decipher the role of plant PP1s, we compared PP1 genes from three monocot species, Brachypodium, common wheat and rice at the genomic and transcriptomic levels. To gain more insight into the wheat PP1 proteins, we identified and characterized TdPP1a, the first wheat type one protein phosphatase from a Tunisian durum wheat variety Oum Rabiaa3. TdPP1a is highly conserved in sequence and structure when compared to mammalian, yeast and other plant PP1s. We demonstrate that TdPP1a is an active, metallo-dependent phosphatase in vitro and is able to interact with AtI2, a typical regulator of PP1 functions. Also, TdPP1a is capable to complement the heat stress sensitivity of the yeast mutant indicating that TdPP1a is functional also in vivo. Moreover, transient expression of TdPP1a::GFP in tobacco leaves revealed that it is ubiquitously distributed within the cell, with a strong accumulation in the nucleus. Finally, transcriptional analyses showed similar expression levels in roots and leaves of durum wheat seedlings. Interestingly, the expression in leaves is significantly induced following salinity stress, suggesting a potential role of TdPP1a in wheat salt stress response.
可逆磷酸化是一种在发育和环境应激反应过程中调节信号转导的重要机制。细胞中大量的去磷酸化事件由1型蛋白磷酸酶（PP1）催化，其催化活性由控制底物特异性或亚细胞定位的调节蛋白的结合驱动。植物含有几种PP1亚型，存在大量功能冗余。虽然动物PP1在控制多种细胞过程中发挥相关作用，但植物直系同源物的研究仍然很少。为了解析植物PP1的作用，我们在基因组和转录组水平上比较了三种单子叶植物短柄草、普通小麦和水稻的PP1基因。为了更深入了解小麦PP1蛋白，我们从突尼斯硬粒小麦品种乌姆·拉比亚3中鉴定并表征了首个小麦1型蛋白磷酸酶TdPP1a。与哺乳动物、酵母和其他植物的PP1相比，TdPP1a在序列和结构上高度保守。我们证明TdPP1a在体外是一种活性的、金属依赖性磷酸酶，并且能够与PP1功能的典型调节因子AtI2相互作用。此外，TdPP1a能够弥补酵母突变体的热胁迫敏感性，表明TdPP1a在体内也具有功能。此外，TdPP1a::GFP在烟草叶片中的瞬时表达表明它在细胞内普遍分布，在细胞核中大量积累。最后，转录分析显示硬粒小麦幼苗的根和叶中表达水平相似。有趣的是，盐胁迫后叶片中的表达显著诱导，表明TdPP1a在小麦盐胁迫反应中可能发挥作用。
