|CARPENTER, MARGARET - New Zealand Institute Of Plant & Food Research|
|COOPER, REBECCA - New Zealand Institute Of Plant & Food Research|
|FREW, TONYA - New Zealand Institute Of Plant & Food Research|
|BUTLER, RUTH - New Zealand Institute Of Plant & Food Research|
|MURRAY, SARAH - New Zealand Institute Of Plant & Food Research|
|MOYA, LEIRE - New Zealand Institute Of Plant & Food Research|
|Coyne, Clarice - Clare|
|TIMMERMAN-VAUGHAN, GAIL - New Zealand Institute Of Plant & Food Research|
Submitted to: Biomed Central (BMC) Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2017
Publication Date: 8/2/2017
Citation: Carpenter, M.A., Cooper, R., Frew, T.J., Butler, R.C., Murray, S.R., Moya, L., Coyne, C.J., Timmerman-Vaughan, G. 2017. Association mapping of variation in starch chain length distribution in pea (Pisum sativum L.) using carbohydrate and starch metabolism candidate genes. Biomed Central (BMC) Plant Biology 17:132. DOI 10.1186/s12870-017-1080-9.
Interpretive Summary: The pulses, or grain legumes, are a subset of the legumes that accumulate starch as a storage component of the seeds. The pulses include economically important species such as pea, chickpea, common bean and lentil. Pulses are relatively high in protein and carbohydrates and relatively low in oil, minerals and vitamins. The carbohydrate composition of pulses includes starch, dietary fiber and oligosaccharides. Pulses also contain phytic acid and phenolic compounds which contribute to their nutritional qualities. Nutritionally, the pulses are characterized by the slow digestibility of their carbohydrate, which gives them relatively low glycaemic index values for carbohydrate-containing foods. Starch is a polymer of glucose moieties with occasional glycosidic branches. Amylose and amylopectin are the two classes of starch. The branching patterns of amylopectin have been described in terms of starch structure. A major aim of the body of research on starch biochemistry and genetics is developing the ability to manipulate starch structure, thereby influencing functional properties and the subsequent uses for starch in food and industrial applications. Research on starch from different botanical sources has indicated that differences in amylopectin influence functional properties such as gelatinisation, enthalpy change and pasting. This manuscript explores the range of variation that exists in pea, both in starch candidate gene allelic variation and in starch structure in pea. Using an association mapping approach, allelic (gene) variants have been identified that show a significant association with variation in starch structure.
Technical Abstract: Although starch consists of large macromolecules composed of glucose units linked by a-1,4-glycosidic linkages with a-1,6-glycosidic branchpoints, variation in starch structural and functional properties is found both within and between species. Research interest in starch genetics is based on the importance of starch in food and industrial processes, with the potential of genetics to provide novel starches. The starch metabolic pathway is complex but has been characterised in diverse plant species, including pea. To understand how allelic variation in the pea starch metabolic pathway can be used to manipulate starch structure and function, partial sequences of 25 candidate genes were characterised for polymorphisms using a panel of 97 diverse pea lines. Variation in the seed starch (amylopectin) chain length distribution, one measure of starch structure, was characterised for these lines using fluorophore-assisted carbohydrate electrophoresis. Association mapping was undertaken to identify polymorphisms associated with the variation in starch chain length distribution, using a mixed linear model that incorporated population structure and kinship. Significant associations were found for polymorphisms in 10 candidate genes plus Mendel’s R locus (the round versus wrinkled seed phenotype). The genes with significantly associated polymorphisms are involved in substrate supply, chain elongation, branching, debranching and degradation stages of the pea carbohydrate and starch metabolic pathway. By identifying polymorphisms in carbohydrate and starch metabolic genes that are associated with variation in amylopectin chain length distribution, we have provided information to guide manipulation of pea seed starch structural and functional properties through plant breeding.