Cross-talk between Copper Homeostasis and Plant Development

由于其强大的化学性质，铜、锌和铁等几种金属在进化过程中被选为许多蛋白质的基本辅因子，这些蛋白质是所有生物生命不可或缺的。植物面临的挑战是，在大多数土壤中，这些基本营养物质的生物可利用浓度通常非常低，而且往往是有限的。因此，金属营养状况可能也会对植物的发育过程产生调节作用，这是可以想象的，也得到了一些零星的实验证据的支持。然而，针对这一问题和潜在调控机制的有针对性的研究很少，金属的可获得性很少被调整到自然环境中常见的水平，甚至在植物发育研究中也很少受到控制。植物铜营养状况强烈影响花的育性和开花时间，但其分子基础尚不清楚。拟南芥的几个启动子结合蛋白(SPL)家族转录因子参与了植物的发育过程，而拟南芥的Spl7突变体在一个控制大量中枢缺铜反应的转录因子中存在缺陷。这些突变体在生理上也比野生型更缺乏铜。此外，在Spl7突变体中，开花时间对缺铜的反应是强烈异常的。在此，我们拟从分子水平阐明铜稳态与开花时间控制之间的相互作用，以及铜稳态网络与内源糖反应之间的调控关系。我们将利用微量营养素控制的生长条件，深入分析植物铜状态和SPL7功能丧失对开花时间的影响。随后，将采用反向遗传方法来剖析铜营养状况、铜稳态网络和开花时间调控网络之间的相互作用。我们将讨论SPL转录因子亚组在铜稳态和金属依赖的植物发育调控中的功能。到目前为止，SPL转录因子的特性还不是很好，也没有被microRNA156靶向。这项工作将揭示如何根据植物的铜营养状况来触发调控过程，铜是一种重要的过渡金属，在所有营养金属阳离子中，铜是与配体分子结合最强的一种。更好地理解铜稳态网络与开花时间控制之间的相互作用，将扩大我们对植物发育代谢控制的知识。最后，这项工作将有助于在生物有效铜缺乏的土壤上提高作物产量和产量质量，这些土壤约占耕种面积的五分之一。

As a result of their potent chemical properties, several metals such as copper, zinc and iron have been selected during evolution for roles as essential cofactors of numerous proteins indispensable for all biological life. Plants are faced with the challenge that in most soils, bioavailable concentrations of these essential nutrients are generally very low, and often limiting. Hence it is conceivable, and supported by some scattered experimental evidence, that metal nutrient status might exert a regulatory influence also on developmental processes in plants. However, targeted studies addressing this and the underlying regulatory mechanisms are scarce, and metal availability has rarely been adjusted to levels common in natural environments, or even controlled, in research on plant development. Plant copper (Cu) nutritional status strongly affects flower fertility and flowering time, but the molecular basis for this is not understood. Whereas several Arabidopsis thaliana Squamosa Promoter binding protein-Like (SPL) family transcription factors have been implicated in plant developmental processes, Arabidopsis thaliana spl7 mutants are defective in a transcription factor that controls a large set of central Cu deficiency responses. These mutants are also physiologically more Cu-deficient than the wild type. Moreover, the response of flowering time to Cu deficiency is strongly aberrant in spl7 mutants. Here we propose to elucidate at the molecular level the cross-talk between Cu homeostasis and flowering time control, as well as the regulatory relationships between the Cu homeostasis network and responses to endogenous sugars. We will employ micronutrient-controlled growth conditions for an in-depth analysis of the influence of plant Cu status and loss of SPL7 function on flowering time. Subsequently, a reverse genetic approach will be pursued to dissect the interactions between Cu nutritional status, the Cu homeostasis network and the regulatory network of flowering time control. We will address the functions of the subgroup of SPL transcription factors which is less well characterized to date and not targeted by microRNA156, in Cu homeostasis and metal-dependent modulation of plant development. This work will reveal how regulatory processes can be triggered dependent on plant nutrient status of Cu, an essential transition metal distinctive by the strongest binding to ligand molecules out of all nutrient metal cations. An improved understanding of the interaction between the copper homeostasis network and flowering time control will expand our knowledge of the metabolic control of plant development. Finally, this work will be instrumental for increasing crop yields and yield quality on soils deficient in bioavailable Cu, which comprise approximately one fifth of the cultivated area.