title: QTLs for enzyme activities and soluble carbohydrates involved in starch accumulation during grain filling in maize.
abstract: ADPglucose, the essential substrate for starch synthesis, is synthesized in maize by a pathway involving at least invertases, sucrose synthase, and ADPglucose pyrophosphorylase, as shown by the starch-deficient mutants, mn1, sh1, and bt2 or sh2, respectively. To improve understanding of the relationship between early grain-filling traits and carbohydrate composition in mature grain, QTLs linked to soluble invertase, sucrose synthase, and ADPglucose pyrophosphorylase activities and to starch, sucrose, fructose, and glucose concentrations were investigated. In order to take into account the specific time-course of each enzyme activity during grain filling, sampling was carried out at three periods (15, 25, and 35 d after pollination) on 100 lines from a recombinant inbred family, grown in the field. The MQTL method associated with QTL interaction analysis revealed numerous QTLs for all traits, but only one QTL was consistently observed at the three sampling periods. Some chromosome zones were heavily labelled, forming clusters of QTLs. Numerous possible candidate genes of the starch synthetic pathway co-located with QTLs. Four QTLs were found close to the locus Sh1 (bin 9.01) coding for the sucrose synthase. In order to confirm the importance of this locus, the CAPS polymorphism of the Sh1 gene was analysed in 45 genetically unrelated maize lines from various geographical origins. The DNA polymorphism was significantly associated with phenotypic traits related to grain filling (starch and amylose content, grain matter, and ADPglucose pyrophosphorylase activity at 35 DAP). Thus, the Sh1 locus could provide a physiologically pertinent marker for maize selection.
authors.affiliation: Laboratoire Structure et Métabolisme des Plantes, Institut de Biotechnologie des Plantes, Bâtiment 630 (UMR 8618/CNRS, UPS), Université Paris-Sud, F-91405 Orsay Cedex, France. thevenot@ibp.u-psud.fr
authors.forename: Claudine
authors.initials: C
authors.lastname: Thévenot
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Simond-Côte
authors.forename: Agnès
authors.initials: A
authors.lastname: Reyss
authors.forename: Domenica
authors.initials: D
authors.lastname: Manicacci
authors.forename: Jacques
authors.initials: J
authors.lastname: Trouverie
authors.forename: Martine
authors.initials: M
authors.lastname: Le Guilloux
authors.forename: Valérie
authors.initials: V
authors.lastname: Ginhoux
authors.forename: Françoise
authors.initials: F
authors.lastname: Sidicina
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Prioul
mesh_terms: D050260:Carbohydrate Metabolism; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D008040:Genetic Linkage; D005819:Genetic Markers; D051599:Glucose-1-Phosphate Adenylyltransferase; D005964:Glucosyltransferases / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000378:metabolism; D010641:Phenotype; D011110:Polymorphism, Genetic; D040641:Quantitative Trait Loci; D012639:Seeds / Q000254:growth & development* / Q000378:metabolism; D013213:Starch / Q000378:metabolism*; D013997:Time Factors; D003313:Zea mays / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism*; D043324:beta-Fructofuranosidase / Q000378:metabolism
chemical_list: D005819:Genetic Markers; D013213:Starch; D005964:Glucosyltransferases; C022699:sucrose synthase; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase; D043324:beta-Fructofuranosidase