Mutation of the plastidial alpha-glucan phosphorylase gene in rice affects the synthesis and structure of starch in the endosperm.
Plastidial phosphorylase (Pho1) accounts for approximately 96% of the total phosphorylase activity in developing rice (Oryza sativa) seeds. From mutant stocks induced by N-methyl-N-nitrosourea treatment, we identified plants with mutations in the Pho1 gene that are deficient in Pho1. Strikingly, the size of mature seeds and the starch content in these mutants showed considerable variation, ranging from shrunken to pseudonormal. The loss of Pho1 caused smaller starch granules to accumulate and modified the amylopectin structure. Variation in the morphological and biochemical phenotype of individual seeds was common to all 15 pho1-independent homozygous mutant lines studied, indicating that this phenotype was caused solely by the genetic defect. The phenotype of the pho1 mutation was temperature dependent. While the mutant plants grown at 30 degrees C produced mainly plump seeds at maturity, most of the seeds from plants grown at 20 degrees C were shrunken, with a significant proportion showing severe reduction in starch accumulation. These results strongly suggest that Pho1 plays a crucial role in starch biosynthesis in rice endosperm at low temperatures and that one or more other factors can complement the function of Pho1 at high temperatures.
Satoh
Hikaru
H
Plant Genetic Resources, Institute of Genetic Resources, Faculty of Agriculture, Kyushu University, Fukuoka 812-8581, Japan. hsatoh@agr.kyushu-u.ac.jp
Shibahara
Kensuke
K
Tokunaga
Takashi
T
Nishi
Aiko
A
Tasaki
Mikako
M
Hwang
Seon-Kap
SK
Okita
Thomas W
TW
Kaneko
Nanae
N
Fujita
Naoko
N
Yoshida
Mayumi
M
Hosaka
Yuko
Y
Sato
Aya
A
Utsumi
Yoshinori
Y
Ohdan
Takashi
T
Nakamura
Yasunori
Y
D001483:Base Sequence; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D008855:Microscopy, Electron, Scanning; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D010641:Phenotype; D006005:Phosphorylases / Q000235:genetics / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000201:enzymology / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D018087:Plastids / Q000201:enzymology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D013213:Starch / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D013696:Temperature
D010940:Plant Proteins; D013213:Starch; D006005:Phosphorylases