2003 Fiscal Year Final Research Report Summary
Search for transporting signal compounds which regulates nodulation of soybean
| Project/Area Number |
13460030
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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 |
Plant nutrition/Soil science
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| Research Institution | Niigata University |
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Principal Investigator |
OHYAMA Takuji NIIGATA UNIVERSITY, Faculty of Agriculture, Professor, 農学部, 教授 (30152268)
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| Co-Investigator(Kenkyū-buntansha) |
OHTAKA Norikuni NIIGATA UNIVERSITY, Faculty of Agriculture, Assistant, 農学部, 助手 (50313507)
SUEYOSHI Kuni NIIGATA UNIVERSITY, Faculty of Agriculture, Associate Professor, 農学部, 助教授 (10216278)
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| Project Period (FY) |
2001 – 2003
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| Keywords | soybean / autoregulation of nodulation / Gaschromatograph-masspectrometer / phytohormone / hypernodulation mut / Indole acetic acid / salicylic acid / nitrate tolerant |
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| Research Abstract |
Soybean plants make root nodules and they can fix atmospheric N_2. The autoregulation of nodulation was found in soybean to prevent the excess nodulation. Recently hypernodulation mutants of soybean, which may lack autoregulatory control of nodulation, were isolated by chemical mutagens. In autoregulation processes, some signal compound(s) may be released from underground part to the shoots by the infection of rhizobia, then the shoots (leaves) make autoregulation signal compound(s) and transport them to the roots and depress nodule growth. However, either "infection signal" or "autoregulation signal" has not been identified yet. We searched these signals using hypernodulation mutants and wild type of soybean cultivar Williams.
We succeeded the sampling of phloem sap from soybean shoot. The peaks of GC-MS, which change after inoculation was searched but consistent result was not obtained. The IAA and ABA could not be detected in the phloem sap.
The concentration of IAA and ABA was analyzed in each part of Williams and its hypernodulation mutant NOD1-3 grown in he field. The IAA concentration was several times higher in Williams nodules than those in NOD1-3, suggesting that IAA translocated from shoot may play as an autoragulation signal.
By supplying salicylic acid in rooting medium, the nodulation of Williams was severely depressed, but not in NOD1-3, suggesting that salicylic acid may be as an candidate for the infection signal of rhizobia.
We found that the growth of individual nodule was quickly and reversibly inhibited by the presence of exogenous nitrate. This was mediated through the decrease in photoassimilate partitioning to nodules. The growth of NOD1-3 nodules was relatively insensitive to nitrate. In NOD1-3, the growth of nodules continued a longer period and photoassimilate paritioning kept higher than in parent Williams.
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