| 研究実績の概要 |
In the first year, I found that AtLPU1 promoter of 6 Arabidopsis accessions containing many polymorphisms (SNPs) had remarkably stronger activity than Col.0., suggesting SNPs found in promoters might be responsible for higher AtLPU1 expression and Pi uptake activity in corresponding accessions. Also, I measured the contents of several lipids in the leaf and chloroplast of WT, oslpu1-KO and OsLPU1-OX seedlings grown under control and low Pi conditions. As a result, Pi deficiency-induced lipid remodeling was alleviated in oslpu1-KO samples indicating OsLPU1 plays a vital role in regulating lipid synthesis in the chloroplasts in response to Pi availability. The relevant results were published in Plant Physiol.
In the second year, to understand the role of LPU1 in regulating lipid accumulation, I compared the phenotypes of atlpu1-KO and the null knockout mutants of lipid biosynthesis genes grown under control and low Pi conditions. The knockout mutants of galactolipid synthesis enzymes showed similar phenotypes with atlpu1-KO seedlings, indicating that AtLPU1 is involved in the reduction of glycolipid synthesis, leading to the reduced Pi uptake activity in roots. I subsequently performed BiFC and yeast two-hybrid assays and found AtLPU1 can directly interact with four enzymes involved in phosphatidic acid (PA) synthesis. Based on these findings, I currently hypothesize that AtLPU1 binds to PA to transfer PA to AtLPPγ for diacylglycerol synthesis. Therefore, in the third year, the interaction between AtLPU1 and PA or enzymes in lipid synthesis should be further investigated.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
As mentioned above, I have carried out most of the experiments planned for the initial two years and have successfully demonstrated that the function of chloroplastic Sec14-like protein LPU1 and its homolog in rice, OsLPU1, played a vital role in plant growth, especially under phosphate deficient condition. Both LPU1 and OsLPU1 were involved in Pi acquisition. OsLPU1 plays a vital role in chloroplast lipid remodeling in response to Pi availability. Related results were summarized in the paper published on Plant Physiology (https://doi.org/10.1093/plphys/kiad212). On the other hand, I have started to identify the role of LPU1 in lipid metabolism. I found the phenotype of galactolipid synthesis enzyme genes knockout mutants was similar to atlpu1-KO seedlings. Also, I confirmed that AtLPU1 can directly interact with phosphatidic acid (PA) metabolism enzymes. I currently speculated that AtLPU1 interacts with lipid synthesis enzymes to be involved in the reduction of glycolipid synthesis, leading to reductions in Pi uptake activity in roots.
Based on these facts, this research project is progressing well according to the original plan for the last year. The experiments planed to reveal the function of LPU1 in phospholipid metabolism will be continued in the last years.
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| 今後の研究の推進方策 |
In the current study, I found that AtLPU1 directly interacts with phosphatidic acid metabolism enzymes. Also, AtLPU1 is involved in the reduction of glycolipid synthesis, leading to reductions in Pi acquisition in roots. However, it remains unclear the molecular basis that what is the role of AtLPU1 in regulating lipid accumulation in chloroplast and further affects the Pi acquisition in roots. Therefore, I will try to identify the binding mode of AtLPU1 and lipid synthesis enzymes and the role of AtLPU1 in lipid biosynthesis. On the other hand, I will explore the potential signaling pathway transmitting chloroplast signaling to roots. The related experiments described in the research plan will be performed in the next years.
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