title: Characterization of pullulanase (PUL)-deficient mutants of rice (Oryza sativa L.) and the function of PUL on starch biosynthesis in the developing rice endosperm.
abstract: Rice (Oryza sativa) allelic sugary1 (sug1) mutants defective in isoamylase 1 (ISA1) accumulate varying levels of starch and phytoglycogen in their endosperm, and the activity of a pullulanase-type of a debranching enzyme (PUL) was found to correlate closely with the severity of the sug1 phenotype. Thus, three PUL-deficient mutants were generated to investigate the function of PUL in starch biosynthesis. The reduction of PUL activity had no pleiotropic effects on the other enzymes involved in starch biosynthesis. The short chains (DP < or = 13) of amylopectin in PUL mutants were increased compared with that of the wild type, but the extent of the changes was much smaller than that of sug1 mutants. The alpha-glucan composition [amylose, amylopectin, water-soluble polysaccharide (WSP)] and the structure of the starch components (amylose and amylopectin) of the PUL mutants were essentially the same, although the average chain length of the B(2-3) chains of amylopectin in the PUL mutant was approximately 3 residues longer than that of the wild type. The double mutants between the PUL-null and mild sug1 mutants still retained starch in the outer layer of endosperm tissue, while the amounts of WSP and short chains (DP < or = 7) of amylopectin were higher than those of the sug1 mutant; this indicates that the PUL function partially overlaps with that of ISA1 and its deficiency has a much smaller effect on the synthesis of amylopectin than ISA1 deficiency and the variation of the sug1 phenotype is not significantly dependent on the PUL activities.
authors.affiliation: Department of Biological Production, Akita Prefectural University, Akita City, Akita, 010-0195 Japan. naokof@akita-pu.ac.jp
authors.forename: Naoko
authors.initials: N
authors.lastname: Fujita
authors.forename: Yoshiko
authors.initials: Y
authors.lastname: Toyosawa
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Utsumi
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Higuchi
authors.forename: Isao
authors.initials: I
authors.lastname: Hanashiro
authors.forename: Akira
authors.initials: A
authors.lastname: Ikegami
authors.forename: Sayuri
authors.initials: S
authors.lastname: Akuzawa
authors.forename: Mayumi
authors.initials: M
authors.lastname: Yoshida
authors.forename: Akiko
authors.initials: A
authors.lastname: Mori
authors.forename: Kotaro
authors.initials: K
authors.lastname: Inomata
authors.forename: Rumiko
authors.initials: R
authors.lastname: Itoh
authors.forename: Akio
authors.initials: A
authors.lastname: Miyao
authors.forename: Hirohiko
authors.initials: H
authors.lastname: Hirochika
authors.forename: Hikaru
authors.initials: H
authors.lastname: Satoh
authors.forename: Yasunori
authors.initials: Y
authors.lastname: Nakamura
mesh_terms: D000687:Amylopectin / Q000378:metabolism; D018533:Biomass; D002152:Calorimetry, Differential Scanning; D050260:Carbohydrate Metabolism; D002850:Chromatography, Gel; D003460:Crystallization; D004548:Elasticity; D006026:Glycoside Hydrolases / Q000172:deficiency*; D016254:Mutagenesis, Insertional; D009154:Mutation / Q000235:genetics*; D012275:Oryza / Q000196:embryology* / Q000201:enzymology*; D011994:Recombinant Proteins / Q000378:metabolism; D012639:Seeds / Q000033:anatomy & histology / Q000196:embryology* / Q000201:enzymology*; D013213:Starch / Q000096:biosynthesis*; D013379:Substrate Specificity; D014783:Viscosity
chemical_list: D011994:Recombinant Proteins; D013213:Starch; D000687:Amylopectin; D006026:Glycoside Hydrolases; C100181:pullulanase