Mechanisms of aluminum induced growth inhibition based on the inhibitory effects of aluminum on sugar transport in plants

铝离子是酸性土壤中抑制作物生长的主要因素。因此，阐明铝毒和耐铝机理将为培育耐铝作物提供必要的基础信息。在这项研究中，这些机制进行了研究，在培养的细胞系统和整个植物系统，重点是糖代谢，这是必要的细胞伸长和根的生长。研究结果如下：1.铝离子抑制烟草细胞对糖的吸收，刺激细胞对糖的消耗，导致细胞水势升高，进而抑制细胞伸长.在整个植物系统中，铝胁迫促进了光合产物向根系的转运.铝诱导的烟草细胞死亡过程与糖饥饿诱导的细胞死亡不同，涉及活性氧的产生、液泡的解体和胞浆钙离子浓度的变化.铝诱导小麦苹果酸分泌的另一个生理意义是维持铝胁迫下根系的生长能力。ALMT1基因上游的重复序列，编码铝激活的苹果酸转运蛋白，似乎控制该基因的表达水平。阐明了ALMT1蛋白的膜拓扑结构.对萌发期的水稻铝敏感突变体进行了分离和鉴定，这些结果表明水稻出现了与能量代谢有关的新的铝敏感症状。这些症状的分子和遗传方面的研究，铝的作用将阐明在糖代谢相关的有机酸分泌，以支持铝耐受性和糖代谢相关的发芽。

A major factor to inhibit crop production in acidic soils is aluminum (Al) ion. Thus the elucidation of mechanisms of Al toxicity and tolerance will be expected to provide basic information necessary for breeding Al-tolerant crops. In this study, these mechanisms were investigated in both cultured cell system and whole plant systems, focusing on sugar metabolism which is necessary for cell elongation and root growth. The findings are as follows:1. Aluminum ion inhibits sugar uptake and stimulates sugar consumption in tobacco cells, which could lead to an increase in water potential and then the inhibition of cell elongation.2. In a whole plant system, the translocation of photoassimilates is stimulated towards the root under Al stress.3. The Al-induced cell death process is different from the sugar-starvation-induced cell death, and involves the production of reactive oxygen species, vacuolar collapse and changes of cytosolic calcium concentration in tobacco cells.4. Another physiological meaning of the Al-triggered malate secretion in wheat is to maintain the growth capability of root under Al stress. The repetitive sequences in the upstream of the ALMT1 gene, encoding the Al-activated malate transporter, seem to control the expression level of the gene. The membrane topology of ALMT1 protein was elucidated.5. Isolation and characterization of Al-sensitive mutants of rice at germination stage were performed.These results indicate novel Al symptoms related to energy metabolism. Molecular and genetical aspects of these symptoms will be studied, and the roles of Al will be elucidated in the sugar metabolism related to the organic acid secretion to support Al tolerance and the sugar metabolism related to germination.