title: Pullulanase and Starch Synthase III Are Associated with Formation of Vitreous Endosperm in Quality Protein Maize.
abstract: The opaque-2 (o2) mutation of maize increases lysine content, but the low seed density and soft texture of this type of mutant are undesirable. Lines with modifiers of the soft kernel phenotype (mo2) called "Quality Protein Maize" (QPM) have high lysine and kernel phenotypes similar to normal maize. Prior research indicated that the formation of vitreous endosperm in QPM might involve changes in starch granule structure. In this study, we focused on analysis of two starch biosynthetic enzymes that may influence kernel vitreousness. Analysis of recombinant inbred lines derived from a cross of W64Ao2 and K0326Y revealed that pullulanase activity had significant positive correlation with kernel vitreousness. We also found that decreased Starch Synthase III abundance may decrease the pullulanase activity and average glucan chain length given the same Zpu1 genotype. Therefore, Starch Synthase III could indirectly influence the kernel vitreousness by affecting pullulanase activity and coordinating with pullulanase to alter the glucan chain length distribution of amylopectin, resulting in different starch structural properties. The glucan chain length distribution had strong positive correlation with the polydispersity index of glucan chains, which was positively associated with the kernel vitreousness based on nonlinear regression analysis. Therefore, we propose that pullulanase and Starch Synthase III are two important factors responsible for the formation of the vitreous phenotype of QPM endosperms.
authors.affiliation: Department of Biology, Baylor University, Waco, Texas, 76798, United States of America.
authors.forename: Hao
authors.initials: H
authors.lastname: Wu
authors.affiliation: Department of Biology, Baylor University, Waco, Texas, 76798, United States of America.
authors.forename: Kasi
authors.initials: K
authors.lastname: Clay
authors.affiliation: Department of Biology, Baylor University, Waco, Texas, 76798, United States of America.
authors.forename: Stephanie S
authors.initials: SS
authors.lastname: Thompson
authors.affiliation: Iowa State University, Department of Biochemistry, Biophysics, and Molecular Biology, Ames, Iowa, 50011, United States of America.
authors.forename: Tracie A
authors.initials: TA
authors.lastname: Hennen-Bierwagen
authors.affiliation: Texas A&M University, Department of Soil and Crop Sciences, College Station, Texas, 77843, United States of America.
authors.forename: Bethany J
authors.initials: BJ
authors.lastname: Andrews
authors.affiliation: Center for Microscopy and Imaging, Baylor University, Waco, Texas, 76798, United States of America.
authors.forename: Bernd
authors.initials: B
authors.lastname: Zechmann
authors.affiliation: Department of Biological Sciences, Florida A&M University, Tallahassee, Florida, 32307, United States of America.
authors.forename: Bryan C
authors.initials: BC
authors.lastname: Gibbon
mesh_terms: D056625:Endosperm / Q000378:metabolism*; D006026:Glycoside Hydrolases / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D013214:Starch Synthase / Q000378:metabolism*; D003313:Zea mays / Q000201:enzymology*
chemical_list: D010940:Plant Proteins; D013214:Starch Synthase; D006026:Glycoside Hydrolases; C100181:pullulanase