Quantitative trait loci and differential gene expression analyses reveal the genetic basis for negatively associated β-carotene and starch content in hexaploid sweetpotato [Ipomoea batatas (L.) Lam.]

• DOI: 10.1007/s00122-019-03437-7
• Publication Date: 2019-10-08T15:12:23Z
• Authors: Dorcus C. Gemenet; Guilherme da Silv...; Bert De Boeck; Joshua C. Wood; Marcelo Mollinari; Bode A. Olukolu; Federico Diaz; Veronica Mosquera; Reuben T. Ssali; Maria David; Mercy N. Kitavi; Gabriela Burgos; Thomas Zum Felde; Marc Ghislain; Edward Carey; Jolien Swanckaert; Lachlan J. M. Coin; Zhangjun Fei; John P. Hamilton; Benard Yada; G. Craig Yencho; Zhao-Bang Zeng; Robert O. M. Mwanga; Awais Khan; Wolfgang J. Grune...; C. Robin Buell
• Keywords: 0301 basic medicine; Amylopectin; Plant Roots; Gene; Biochemistry; 630; Agricultural and Biological Sciences; Food science; Sociology; Gene Expression Regulation, Plant; sweet potatoes; genetics; Ipomoea batatas; Starch synthase; 2. Zero hunger; starch; carotenoids; Life Sciences; Starch; Chromoplast; Orange (colour); General Medicine; beta Carotene; FOS: Sociology; Phenotype; 1305 Biotechnology; Original Article; Biotechnology; biotechnology; Quantitative trait locus; 570; Phytoene synthase; Plastid; Quantitative Trait Loci; Population; Environment; Horticulture; Biosynthesis; ipomoea batatas; Chloroplast; Polyploidy; 03 medical and health sciences; Quantitative Trait, Heritable; 1311 Genetics; Genetics; 1102 Agronomy and Crop Science; Biology; Alleles; Genetic Association Studies; Demography; Soil Fertility; Botany; Cacao Agroforestry Management and Conservation; FOS: Biological sciences; gene expression; Locus (genetics); Amylose; Agronomy and Crop Science

AbstractKey messageβ-Carotene content in sweetpotato is associated with theOrangeandphytoene synthasegenes; due to physical linkage ofphytoene synthasewithsucrose synthase, β-carotene and starch content are negatively correlated.AbstractIn populations depending on sweetpotato for food security, starch is an important source of calories, while β-carotene is an important source of provitamin A. The negative association between the two traits contributes to the low nutritional quality of sweetpotato consumed, especially in sub-Saharan Africa. Using a biparental mapping population of 315 F1progeny generated from a cross between an orange-fleshed and a non-orange-fleshed sweetpotato variety, we identified two major quantitative trait loci (QTL) on linkage group (LG) three (LG3) and twelve (LG12) affecting starch, β-carotene, and their correlated traits, dry matter and flesh color. Analysis of parental haplotypes indicated that these two regions acted pleiotropically to reduce starch content and increase β-carotene in genotypes carrying the orange-fleshed parental haplotype at the LG3 locus.Phytoene synthaseandsucrose synthase,the rate-limiting and linked genes located within the QTL on LG3 involved in the carotenoid and starch biosynthesis, respectively, were differentially expressed in Beauregard versus Tanzania storage roots. TheOrangegene, the molecular switch for chromoplast biogenesis, located within the QTL on LG12 while not differentially expressed was expressed in developing roots of the parental genotypes. We conclude that these two QTL regions act together in acisandtransmanner to inhibit starch biosynthesis in amyloplasts and enhance chromoplast biogenesis, carotenoid biosynthesis, and accumulation in orange-fleshed sweetpotato. Understanding the genetic basis of this negative association between starch and β-carotene will inform future sweetpotato breeding strategies targeting sweetpotato for food and nutritional security.