期刊
JOURNAL OF EXPERIMENTAL BOTANY
卷 72, 期 7, 页码 2570-2583出版社
OXFORD UNIV PRESS
DOI: 10.1093/jxb/erab016
关键词
ADP-glucose pyrophosphorylase; grain filling; high-yielding; rice; Oryza sativa; sink activity; sink strength; C-13 labelling; starch synthesis
资金
- Cabinet Office, Government of Japan, Cross-ministerial Strategic Innovation Promotion Program, through the 'Technologies for creating next-generation agriculture, forestry and fisheries' - Bio-oriented Technology Research Advancement Institution, NARO
- JSPS KAKENHI [JP20K15511]
The study investigated carbon flow in three high-yielding rice cultivars and found that in 'Momiroman', newly fixed carbon assimilates were stored as hexose instead of being converted to starch. Additionally, lower activity of ADP-glucose pyrophosphorylase and lower expression of AGPS2b in 'Momiroman' grains may be the main reasons for slower starch synthesis and lower sink activity in this cultivar.
Understanding the limiting factors of grain filling is essential for the further improvement of grain yields in rice (Oryza sativa). The relatively slow grain growth of the high-yielding cultivar 'Momiroman' is not improved by increasing carbon supply, and hence low sink activity (i.e. the metabolic activity of assimilate consumption/storage in sink organs) may be a limiting factor for grain filling. However, there is no metabolic evidence to corroborate this hypothesis, partly because there is no consensus on how to define and quantify sink activity. In this study, we investigated the carbon flow at a metabolite level from photosynthesis in leaves to starch synthesis in grains of three high-yielding cultivars using the stable isotope C-13. We found that a large amount of newly fixed carbon assimilates in Momiroman was stored as hexose instead of being converted to starch. In addition, the activity of ADP-glucose pyrophosphorylase and the expression of AGPS2b, which encodes a subunit of the ADP-glucose pyrophosphorylase enzyme, were both lower in Momiroman than in the other two cultivars in grains in superior positions on panicle branches. Hence, slower starch synthesis from hexose, which is partly explained by the low expression level of AGPS2b, may be the primary metabolic reason for the lower sink activity observed in Momiroman.
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