| Project/Area Number |
17370023
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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 |
Morphology/Structure
|
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| Research Institution | Okayama University |
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Principal Investigator |
TAKAHASHI Taku Okayama University, GRADUATE SCHOOL OF NATURAL SCIENCE AND TECHNOLOGY, PROFESSOR (20271710)
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| Project Period (FY) |
2005 – 2007
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| Project Status |
Completed (Fiscal Year 2007)
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| Budget Amount *help |
¥15,280,000 (Direct Cost: ¥14,500,000、Indirect Cost: ¥780,000)
Fiscal Year 2007: ¥3,380,000 (Direct Cost: ¥2,600,000、Indirect Cost: ¥780,000)
Fiscal Year 2006: ¥4,000,000 (Direct Cost: ¥4,000,000)
Fiscal Year 2005: ¥7,900,000 (Direct Cost: ¥7,900,000)
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| Keywords | ARABLDOPSIS / POLYAMINE / DEVELOPMENT / MUTANT / MOLECULAR GENETICS |
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| Research Abstract |
Disruption of the Arabidopsis thaliana ACAULIS5 (ACL5) gene results in a severe dwarf phenotype. To elucidate ACL5-mediated regulatory pathways of the stem growth, we isolated four suppressor of acaulis (sac) mutants that reverse the dwarf phenotype. Our results revealed that the sac51-d mutation disrupts a short upstream open reading frame (uORF) of SAC51, which encodes a putative transcription factor and suggested that ACL5 plays a role in translational activation of SAC51.
A gene responsible for sac52-d was found to encode a ribosomal protein RPL10A.
We also identified three genes in the moss P. patens which are homologous to ACL5.
Furthermore, to examine whether ACL5 encodes spermine synthase or thermospermine synthase, we tried to detect these polyamines in plant extracts. The results revealed that thermospermine is detected in wild-type seedlings but is not detectable in the ac15-1 mutant. We further examined the effect of exogenous application of these isomers on the growth of ac15-1. Daily application of thermospermine onto the shoot apex partially rescued the dwarf phenotype of ac15-1, while that of spermine had no effects on the morphology of the mutant. The ac15-1 transcript level in ac15-1 seedlings, which is much higher than the ACL5 transcript level in wild-type seedlings, was found to be reduced by thermospermine. Thus it was concluded that thermospermine is produced through the action of ACL5 and required for stem elongation in Arabidopsis.
On the other hand, physiological studies on the mutant of SPMS, which encodes spermine synthase, revealed that spermine plays a protective role in drought and high salt stress responses. These results should provide a important due in understanding the action of polyamines in plant growth and development.
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