Sugars are the main building blocks for carbohydrate storage, but also serve as signaling molecules and protective compounds during abiotic stress responses. Accordingly, sugar transport proteins fulfill multiple roles as they mediate long distance sugar allocation, but also shape the subcellular and tissue-specific carbohydrate profiles by balancing the levels of these molecules in various compartments. Accordingly, transporter activity represents a target by classical or directed breeding approaches, to either, directly increase phloem loading or to increase sink strength in crop species. The relative subcellular distribution of sugars is critical for molecular signaling affecting yield-relevant processes like photosynthesis, onset of flowering and stress responses, while controlled long-distance sugar transport directly impacts development and productivity of plants. However, long-distance transport is prone to become unbalanced upon adverse environmental conditions. Therefore, we highlight the influence of stress stimuli on sucrose transport in the phloem and include the role of stress induced cellular carbohydrate sinks, like raffinose or fructans, which possess important roles to build up tolerance against challenging environmental conditions. In addition, we report on recent breeding approaches that resulted in altered source and sink capacities, leading to increased phloem sucrose shuttling in crops. Finally, we present strategies integrating the need of cellular stress-protection into the general picture of long-distance transport under abiotic stress, and point to possible approaches improving plant performance and resource allocation under adverse environmental conditions, leading to stabilized or even increased crop yield.

中文翻译：

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在非生物胁迫下改善资源分配和稳定产量

糖是碳水化合物储存的主要组成部分，但在非生物胁迫反应中也可作为信号分子和保护性化合物。因此，糖转运蛋白在介导长距离糖分配时发挥多种作用，而且还通过平衡这些分子在各个区室中的水平来塑造亚细胞和组织特异性碳水化合物谱。因此，转运蛋白活性代表了经典或定向育种方法的目标，直接增加韧皮部负载或增加作物物种的库强度。糖的相对亚细胞分布对于影响产量相关过程的分子信号传导至关重要，如光合作用、开花的开始和应激反应，而受控的长距离糖分运输直接影响植物的发育和生产力。然而，长途运输容易在不利的环境条件下变得不平衡。因此，我们强调了压力刺激对韧皮部中蔗糖转运的影响，并包括压力诱导的细胞碳水化合物汇的作用，如棉子糖或果聚糖，它们在建立对具有挑战性的环境条件的耐受性方面具有重要作用。此外，我们报告了最近导致源和汇能力改变的育种方法，导致韧皮部蔗糖在作物中穿梭增加。最后，我们提出了将细胞应激保护的需求整合到非生物应激下长距离运输的总体情况中的策略，