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所有生物生命不可或缺的许多蛋白质的重要辅助因子。植物面临的挑战是，在大多数土壤中，这些必需营养素的生物可利用浓度通常非常低，而且往往是有限的。因此，可以想象，并支持一些分散的实验证据，金属营养状况可能会产生调节影响，也对植物的发育过程。然而，针对这一问题和潜在的调控机制的有针对性的研究很少，在植物发育研究中，金属的可获得性很少被调整到自然环境中常见的水平，甚至很少受到控制。植物铜（Cu）营养状况强烈影响花的生育力和开花时间，但这是不了解的分子基础。而几个拟南芥鳞状启动子结合蛋白样（SPL）家族转录因子已牵连在植物发育过程中，拟南芥spl7突变体是有缺陷的转录因子，控制了一个大的中央铜缺乏反应。这些突变体在生理上也比野生型更缺乏Cu。此外，开花时间的反应，铜缺乏是强烈异常的spl7突变体。在这里，我们建议在分子水平上阐明铜稳态和开花时间控制之间的串扰，以及铜稳态网络和响应内源性糖之间的调节关系。我们将采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，一个反向遗传的方法将追求剖析铜营养状况，铜稳态网络和开花时间控制的调节网络之间的相互作用。我们将讨论SPL转录因子亚组的功能，该亚组迄今为止特征不太清楚，并且不被microRNA156靶向，在铜稳态和植物发育的金属依赖性调节中。这项工作将揭示如何调控过程可以触发依赖于植物营养状况的铜，一个重要的过渡金属独特的最强结合配体分子的所有营养金属阳离子。对铜稳态网络和开花时间控制之间相互作用的进一步理解将扩大我们对植物发育代谢控制的认识。最后，这项工作将有助于提高作物产量和产量质量的土壤缺乏生物有效铜，其中包括约五分之一的耕地面积。

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.