2006 Fiscal Year Final Research Report Summary
Studies for structural change of amylopectin by granule-bound starch synthase I and pasting property of the starch granules.
| Project/Area Number |
16380084
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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 |
Food science
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| Research Institution | Niigata University |
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Principal Investigator |
ITOH Kimiko Niigata University, Institute of Science and Technology, Associate Professor, 自然科学系, 助教授 (10281007)
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| Co-Investigator(Kenkyū-buntansha) |
HANASHIRO Isao Kagoshima University, Faculty of Agriculture, Associate professor, 農学部, 助教授 (30336325)
MITSUI Toshiaki Niigata University, Institute of Science and Technology, Professor, 自然科学系, 教授 (70183960)
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| Project Period (FY) |
2004 – 2006
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| Keywords | Amylopectin / Extra long chain / GBSSI / starch / Waxy |
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| Research Abstract |
A rice Wx^a gene encoding for a granule-bound starch synthase I (GBSSI) was introduced into japonica-type waxy rice (cultivars Iwaimochi and Musashimochi) and its effect on structures and pasting properties of endosperm starches was examined. Apparent amylose content determined by high-performance size-exclusion chromatography of debranched starch increased from undetectable amount for the parent waxy cultivars to 21.6-22.2% for the transgenic lines. Similar analyses of debranched amylopectin revealed existence of a significant amount (7.5-8.4% by weight) of long unit-chains (LC), which appeared in the same elution position as amylose. Taking into account the LC content, actual amylose content was calculated to be 14.9-16.0% for the transgenic lines. No significant difference was found in chain-length distribution for the A, B_1, and B_2+B_3 fractions, indicating the effect by the transgene on amylopectin structure was essentially specific in LC formation. Since Labelle amylopectin con
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tains LC only slightly (0.6% by weight), as yet determined factor(s) other than GBSS activity is thought to be involved in control of formation and/or the amount of LC formed. LC isolated from debranched amylopectin by 1-butanol precipitation exhibited number-average degree of polymerization (DPn) of 350-390 and DP distribution distinct from amylose. Structure of amylose was slightly different between Labelle and the transgenic lines, and yet the latter amyloses had characteristics of indica rice rather than japonica rice. Pasting properties examined with a Rapid Visco Analyzer showed the GBSS expression caused elevation of pasting temperature, a decrease in peak viscosity by half, a large decrease in breakdown, indicating the altered starch structures resulted in starch granules less susceptible to swelling.
Wx genomic DNA was analyzed and structural differences were determined between non-LC type cultivar and LC-type cultivar or transgenic lines. The two point mutations were commonly found in genomic structure at non-LC type cultivar and the mutations can lead to changes in amino acids sequence of WX protein. Less
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