小柯机器人

近日，丹麦哥本哈根大学Barbara Ann Halkier等研究人员合作发现，防御性芥子油苷的输出是其在种子中积累的关键。该项研究成果于2023年4月19日在线发表在《自然》杂志上。

研究人员确定了拟南芥中的USUALLY MULTIPLE AMINO ACIDS MOVE IN AND OUT TRANSPORTER（UMAMIT）家族的成员-UMAMIT29、UMAMIT30和UMAMIT31是具有单向转运机制的芥子油苷输出蛋白。功能缺失的umamit29 umamit30 umamit31三突变体的种子芥子油苷含量非常低，表明这些转运体在将芥子油苷转运到种子中发挥了关键作用。研究人员提出了一个模型，其中UMAMIT单转运体促进芥子油苷从生物合成细胞沿电化学梯度流出到植物体，在那里高亲和力的H⁺耦合芥子油苷输入蛋白GLUCOSINOLATE TRANSPORTERS（GTR）将它们装入韧皮部，并转送到种子中。这些研究结果验证了这一理论，即细胞养分平衡需要两种不同的能量化转运蛋白类型。UMAMIT输出蛋白是新的分子靶标，可以在不改变防御化合物在整个植物中的分布的情况下，提高芸苔属油料种子作物的营养价值。

据了解，控制代谢物分布的植物膜转运器对关键的农艺性状有贡献。为了消除作物可食用部分的抗营养因子，导入蛋白的突变可以阻断这些因子在吸收组织中的积累。然而，这往往会导致植物内部的分布模式发生重大改变，而输出蛋白的工程化可以防止这种分布的变化。在芸苔属油料种子作物中，抗营养的芥子油苷防御化合物被转移到种子中。然而，芥子油苷出口工程化的分子靶标仍然不清楚。

附：英文原文

Title: Export of defensive glucosinolates is key for their accumulation in seeds

Author: Xu, Deyang, Sanden, Niels Christian Holm, Hansen, Line Lykke, Belew, Zeinu Mussa, Madsen, Svend Roesen, Meyer, Lasse, Jrgensen, Morten Egevang, Hunziker, Pascal, Veres, Dorottya, Crocoll, Christoph, Schulz, Alexander, Nour-Eldin, Hussam Hassan, Halkier, Barbara Ann

Issue&Volume: 2023-04-19

Abstract: Plant membrane transporters controlling metabolite distribution contribute key agronomic traits1,2,3,4,5,6. To eliminate anti-nutritional factors in edible parts of crops, the mutation of importers can block the accumulation of these factors in sink tissues7. However, this often results in a substantially altered distribution pattern within the plant8,9,10,11,12, whereas engineering of exporters may prevent such changes in distribution. In brassicaceous oilseed crops, anti-nutritional glucosinolate defence compounds are translocated to the seeds. However, the molecular targets for export engineering of glucosinolates remain unclear. Here we identify and characterize members of the USUALLY MULTIPLE AMINO ACIDS MOVE IN AND OUT TRANSPORTER (UMAMIT) family—UMAMIT29, UMAMIT30 and UMAMIT31—in Arabidopsis thaliana as glucosinolate exporters with a uniport mechanism. Loss-of-function umamit29 umamit30 umamit31 triple mutants have a very low level of seed glucosinolates, demonstrating a key role for these transporters in translocating glucosinolates into seeds. We propose a model in which the UMAMIT uniporters facilitate glucosinolate efflux from biosynthetic cells along the electrochemical gradient into the apoplast, where the high-affinity H+-coupled glucosinolate importers GLUCOSINOLATE TRANSPORTERS (GTRs) load them into the phloem for translocation to the seeds. Our findings validate the theory that two differently energized transporter types are required for cellular nutrient homeostasis13. The UMAMIT exporters are new molecular targets to improve nutritional value of seeds of brassicaceous oilseed crops without altering the distribution of the defence compounds in the whole plant.

DOI: 10.1038/s41586-023-05969-x

Source: https://www.nature.com/articles/s41586-023-05969-x

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