Expression patterns of genes encoding carbohydrate-metabolizing enzymes and their relationship to grain filling in rice (Oryza sativa L.): comparison of caryopses located at different positions in a panicle.
In rice, caryopses located at the base of the panicle have a lower growth rate than those at the tip of the panicle. The former and latter types of caryopses are called inferior and superior caryopses, respectively. Taking the different growth rate into consideration, sugar status and the expression of genes encoding carbohydrate-metabolizing enzymes in inferior caryopses were compared with those in superior caryopses. During the first 5 d after flowering, superior caryopses elongated rapidly, but inferior caryopses did not. At this phase, inferior caryopses had a low ratio of hexose to sucrose, high activity of acid invertase and the absence of the expression of the genes encoding the above enzymes except for two isoforms of cell wall invertase, OsCIN4 and INV1, in comparison with superior caryopses. At the start of caryopsis elongation in both superior and inferior caryopses, the hexose/sucrose ratio increased accompanied by gene expression of vacuolar invertase (INV3), sucrose synthase (RSus1) and ADP-glucose pyrophosphorylase (AGP-L2: D50317). Furthermore, the genes related to endospermal starch accumulation were expressed highly with the decrease in the hexose/sucrose ratio after its peak. Based on the comparison of superior and inferior caryopses, the possible mechanism of grain filling in rice is discussed.
Ishimaru
Tsutomu
T
Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo, 113-8657 Japan. aa17002@hotmail.com
Hirose
Tatsuro
T
Matsuda
Toshiaki
T
Goto
Akitoshi
A
Takahashi
Kazunari
K
Sasaki
Haruto
H
Terao
Tomio
T
Ishii
Ryu-ichi
R
Ohsugi
Ryu
R
Yamagishi
Tohru
T
D050260:Carbohydrate Metabolism; D002473:Cell Wall / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D051599:Glucose-1-Phosphate Adenylyltransferase; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D009713:Nucleotidyltransferases / Q000235:genetics / Q000378:metabolism; D012275:Oryza / Q000201:enzymology* / Q000235:genetics* / Q000254:growth & development; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000201:enzymology; D043324:beta-Fructofuranosidase / Q000235:genetics / Q000378:metabolism
D010940:Plant Proteins; D005964:Glucosyltransferases; C022699:sucrose synthase; D009713:Nucleotidyltransferases; D051599:Glucose-1-Phosphate Adenylyltransferase; D043324:beta-Fructofuranosidase