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

在植物中，像碳水化合物和氨基酸（aa）这样的营养物质需要在源组织和汇组织之间进行分配，以确保足够的供应和最终的生存。特别是在应对能量限制条件下，需要能量稳态和营养分配的紧密协调。最近，我们定义了Snf1相关的KINASE1 （SnRK1）和控制aa分解代谢的C/S1碱性亮氨酸拉链（bZIP）转录因子的下游网络，以维持黑暗诱导衰老（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进出转运蛋白（UMAMITs）联系起来，UMAMITs在植物中起促进作用。UMAMIT33在DIS过程中被转录诱导，并定位于细胞质中，我们认为UMAMIT33参与细胞内aa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信号的转录调控。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aa分布和aa从黑暗处理的叶片输出。以UMAMIT33为例，我们将在DIS中进一步研究1-2个S1-bZIP调节的UMAMITs，这些UMAMITs是通过无偏倚转录组研究选择的。后一种方法还将提供由SnRK1-C/S1 bZIP低能量网络协调的来自其他家族的转运体的全面概述。由于胁迫下的养分分配会显著影响作物的重要农艺性状，如产量和收获后的货架期，本基础研究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.