2006 Fiscal Year Final Research Report Summary
Structure of aluminum tolerant factor isolated from Aspergillus niger and its application to Aluminum-tolerant higher plants
| Project/Area Number |
16380067
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied biochemistry
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| Research Institution | The University of Tokyo |
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Principal Investigator |
YOSHIMURA Etsuro The University of Tokyo, Graduate School of Agricultural and Life Sciences, Professor, 大学院農学生命科学研究科, 教授 (10130303)
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| Co-Investigator(Kenkyū-buntansha) |
TASHIRO Mitsuru Meisei University, College of Science and Technology, Associate Professor, 理工学部, 助教授 (40315750)
NAKANISHI Hiromi The University of Tokyo, Graduate School of Agricultural and Life Sciences, Assistant, 大学院農学生命科学研究科, 助手 (80282698)
TASHIRO Sakurako Tokyo University of Pharmacy and Life Science, School of Pharmacy and School of Life Science, Lecturer, 薬学部, 講師 (40328555)
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| Project Period (FY) |
2004 – 2006
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| Keywords | aluminum / Apergillus niger / 2-isopropylmalate / Saccharomyces cerevisiae / Arabidopsis thaliana |
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| Research Abstract |
Aluminum toxicity is one of the factors that limit plant growth in acid soils. To ameliorate the toxicity, some plant species secret organic anions that bind Al ions. The fungi Apergillus niger secrets large amounts of citrate, as known as citric acid fermentation. This led to a hypothesis that this fungi possesses some aluminum tolerant mechanisms. From this viewpoint, the budding yeast Saccharomyces cerevisiae was transformed with cDNA from A niger. Screening system was devised to obtain aluminum tolerant yeast strains and seven genes were identified as aluminum tolerant factors. Although these genes are unlikely to be related to citrate synthesis and its secretion, the gene, AnATF5 can be related to synthesis of the organic acid anion, 2-isopropylmalate (2-iPMA). This organic anion may play a role in detoxification of aluminum in the yeast. This is because an increase in 2-iPMA concentration enhanced the growth of the yeast cultured in the presence of aluminum and because deletion of genes that are associated to 2-iPMA synthesis rendered the yeast aluminum synthesis. Three genes were cloned from Arabidopsis thaliana to generate aluminum tolerant higher plant and over-expressed in the plant. However, no difference in the growth between the transgenic plants and its vector control in aluminum containing media. The reason for this has so far been unclear and further study is needed.
Until now, aluminum tolerant plants have been generated which rely on organic acid overproduction and on its secretion. These acids are all ones related to TCA cycle, such as malate and citrate. In contrast to this, 2-iPMA is intermediate of leucine biosynthesis. When further study will enable us to obtain an aluminum tolerant transgenic plant that overproduce 2-iPMA, the plants might be superior over the transgenic plants relying on TCA cycle organic acids, since 2-IPMA is not dependent on energy producing processes.
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