Overlapping functions of the starch synthases SSII and SSIII in amylopectin biosynthesis in <it>Arabidopsis</it>
<p>Abstract</p> <p>Background</p> <p>The biochemical mechanisms that determine the molecular architecture of amylopectin are central in plant biology because they allow long-term storage of reduced carbon. Amylopectin structure imparts the ability to form semi-crystalli...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
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BMC
2008-09-01
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| Series: | BMC Plant Biology |
| Online Access: | http://www.biomedcentral.com/1471-2229/8/96 |
| _version_ | 1818334896491331584 |
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| author | D'Hulst Christophe Delvallé David Szydlowski Nicolas Zhang Xiaoli James Martha G Myers Alan M |
| author_facet | D'Hulst Christophe Delvallé David Szydlowski Nicolas Zhang Xiaoli James Martha G Myers Alan M |
| author_sort | D'Hulst Christophe |
| collection | DOAJ |
| description | <p>Abstract</p> <p>Background</p> <p>The biochemical mechanisms that determine the molecular architecture of amylopectin are central in plant biology because they allow long-term storage of reduced carbon. Amylopectin structure imparts the ability to form semi-crystalline starch granules, which in turn provides its glucose storage function. The enzymatic steps of amylopectin biosynthesis resemble those of the soluble polymer glycogen, however, the reasons for amylopectin's architectural distinctions are not clearly understood. The multiplicity of starch biosynthetic enzymes conserved in plants likely is involved. For example, amylopectin chain elongation in plants involves five conserved classes of starch synthase (SS), whereas glycogen biosynthesis typically requires only one class of glycogen synthase.</p> <p>Results</p> <p>Null mutations were characterized in <it>AtSS2</it>, which codes for SSII, and mutant lines were compared to lines lacking SSIII and to an <it>Atss2</it>, <it>Atss3 </it>double mutant. Loss of SSII did not affect growth rate or starch quantity, but caused increased amylose/amylopectin ratio, increased total amylose, and deficiency in amylopectin chains with degree of polymerization (DP) 12 to DP28. In contrast, loss of both SSII and SSIII caused slower plant growth and dramatically reduced starch content. Extreme deficiency in DP12 to DP28 chains occurred in the double mutant, far more severe than the summed changes in SSII- or SSIII-deficient plants lacking only one of the two enzymes.</p> <p>Conclusion</p> <p>SSII and SSIII have partially redundant functions in determination of amylopectin structure, and these roles cannot be substituted by any other conserved SS, specifically SSI, GBSSI, or SSIV. Even though SSIII is not required for the normal abundance of glucan chains of DP12 to DP18, the enzyme clearly is capable of functioning in production such chains. The role of SSIII in producing these chains cannot be detected simply by analysis of an individual mutation. Competition between different SSs for binding to substrate could in part explain the specific distribution of glucan chains within amylopectin.</p> |
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| institution | Directory Open Access Journal |
| issn | 1471-2229 |
| language | English |
| last_indexed | 2024-12-13T14:14:49Z |
| publishDate | 2008-09-01 |
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| spelling | doaj.art-107e8ef21e244f45a8d99a90260aed862022-12-21T23:42:21ZengBMCBMC Plant Biology1471-22292008-09-01819610.1186/1471-2229-8-96Overlapping functions of the starch synthases SSII and SSIII in amylopectin biosynthesis in <it>Arabidopsis</it>D'Hulst ChristopheDelvallé DavidSzydlowski NicolasZhang XiaoliJames Martha GMyers Alan M<p>Abstract</p> <p>Background</p> <p>The biochemical mechanisms that determine the molecular architecture of amylopectin are central in plant biology because they allow long-term storage of reduced carbon. Amylopectin structure imparts the ability to form semi-crystalline starch granules, which in turn provides its glucose storage function. The enzymatic steps of amylopectin biosynthesis resemble those of the soluble polymer glycogen, however, the reasons for amylopectin's architectural distinctions are not clearly understood. The multiplicity of starch biosynthetic enzymes conserved in plants likely is involved. For example, amylopectin chain elongation in plants involves five conserved classes of starch synthase (SS), whereas glycogen biosynthesis typically requires only one class of glycogen synthase.</p> <p>Results</p> <p>Null mutations were characterized in <it>AtSS2</it>, which codes for SSII, and mutant lines were compared to lines lacking SSIII and to an <it>Atss2</it>, <it>Atss3 </it>double mutant. Loss of SSII did not affect growth rate or starch quantity, but caused increased amylose/amylopectin ratio, increased total amylose, and deficiency in amylopectin chains with degree of polymerization (DP) 12 to DP28. In contrast, loss of both SSII and SSIII caused slower plant growth and dramatically reduced starch content. Extreme deficiency in DP12 to DP28 chains occurred in the double mutant, far more severe than the summed changes in SSII- or SSIII-deficient plants lacking only one of the two enzymes.</p> <p>Conclusion</p> <p>SSII and SSIII have partially redundant functions in determination of amylopectin structure, and these roles cannot be substituted by any other conserved SS, specifically SSI, GBSSI, or SSIV. Even though SSIII is not required for the normal abundance of glucan chains of DP12 to DP18, the enzyme clearly is capable of functioning in production such chains. The role of SSIII in producing these chains cannot be detected simply by analysis of an individual mutation. Competition between different SSs for binding to substrate could in part explain the specific distribution of glucan chains within amylopectin.</p>http://www.biomedcentral.com/1471-2229/8/96 |
| spellingShingle | D'Hulst Christophe Delvallé David Szydlowski Nicolas Zhang Xiaoli James Martha G Myers Alan M Overlapping functions of the starch synthases SSII and SSIII in amylopectin biosynthesis in <it>Arabidopsis</it> BMC Plant Biology |
| title | Overlapping functions of the starch synthases SSII and SSIII in amylopectin biosynthesis in <it>Arabidopsis</it> |
| title_full | Overlapping functions of the starch synthases SSII and SSIII in amylopectin biosynthesis in <it>Arabidopsis</it> |
| title_fullStr | Overlapping functions of the starch synthases SSII and SSIII in amylopectin biosynthesis in <it>Arabidopsis</it> |
| title_full_unstemmed | Overlapping functions of the starch synthases SSII and SSIII in amylopectin biosynthesis in <it>Arabidopsis</it> |
| title_short | Overlapping functions of the starch synthases SSII and SSIII in amylopectin biosynthesis in <it>Arabidopsis</it> |
| title_sort | overlapping functions of the starch synthases ssii and ssiii in amylopectin biosynthesis in it arabidopsis it |
| url | http://www.biomedcentral.com/1471-2229/8/96 |
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