Regulation and function of Arabidopsis UMAMIT amino acid transport facilitators in response to dark-induced energy starvation

在植物中，碳水化合物和氨基酸(AA)等营养物质需要在源组织和库组织之间进行分配，以确保足够的供应，从而确保生存。特别是在应对能量限制的情况下，能量平衡和营养分配的紧密协调是必要的。最近，我们定义了Snf1相关激酶1(SnRK1)和C/S1碱性亮氨酸拉链(BZIP)转录因子的下游网络，这些转录因子控制AA的分解代谢，以支持暗诱导衰老(DIS)期间线粒体ATP的合成。在这个项目中，我们的目标是将SnRK1-C/S1-bZIP信号与通常多个氨基酸的移入和移出转运体(UMAMITs)联系起来，UMAMITs在植物中扮演AA促进器的角色。UMAMIT33在DIS过程中被转录诱导，并定位于液泡膜，我们认为UMAMIT33参与了细胞内AA的分配。因此，本项目研究了UMAMIT33的细胞定位、表达模式、转运体生理以及SnRK1-C/S1-bZIP-信号对转录的调控。为了深入了解其功能，将分析失去功能的植物的表型和分子DIS反应、细胞内AA的分布以及暗处理叶片中AA的输出。如UMAMIT33所示，我们将进一步研究1-2个S1-bZIP调控的DIS中的UMAMITs，由一项无偏见的转录组研究选择。后一种方法还将全面概述由SnRK1-C/S1 bZIP低能量网络协调的其他家族的转运体。由于胁迫期间的养分分配显著影响产量和收获后货架期等重要农艺性状，这项基础研究获得的见解可能为未来作物改良提供新的策略。

In plants, nutrients like carbohydrates and amino acids (aa) need to be allocated between source and sink tissues to assure sufficient supply and consequently survival. Particularly in response to energy limiting conditions, a tight co-ordination of energy homeostasis and nutrient allocation is required. Recently, we defined the Snf1 RELATED KINASE1 (SnRK1) and the down-stream network of C/S1 basic leucine zipper (bZIP) transcription factors controlling aa catabolism to sustain mitochondrial ATP synthesis during dark-induced senescence (DIS). In this project, we aim at linking SnRK1-C/S1-bZIP signalling to the USUALLY MULTIPLE AMINO ACIDS MOVE IN AND OUT TRANSPORTERS (UMAMITs), which perform as aa facilitators in plants. Being transcriptionally induced during DIS, and localized in the tonoplast, we propose that UMAMIT33 is involved in intracellular aa allocation. Hence, this project studies the cellular localization of UMAMIT33, its expression patterns, transporter physiology and transcriptional regulation by SnRK1-C/S1-bZIP-signalling. To gain insight into its function, loss-of-function plants will be analysed for phenotypical and molecular DIS responses, cellular aa distribution and aa export from the dark-treated leaves. As exemplified for UMAMIT33, we will study 1-2 further S1-bZIP regulated UMAMITs in DIS, selected by an unbiased transcriptome study. The latter approach will also provide a comprehensive overview of transporters from other families co-ordinated by the SnRK1-C/S1 bZIP low energy network. As nutrient allocation during stress significantly influence agronomical important properties such as yield and post-harvest shelf-life, the insights gained by this basic research may provide novel strategies for future crop improvement.