Analysis of carbon flow at the metabolite level reveals that starch synthesis from hexose is a limiting factor in a high-yielding rice cultivar. (22nd January 2021)

• Record Type: Journal Article
• Authors: Okamura, Masaki; Hirai, Masami Yokota; Sawada, Yuji; Okamoto, Mami; Oikawa, Akira; Sasaki, Ryosuke; Arai-Sanoh, Yumiko; Mukouyama, Takehiro; Adachi, Shunsuke; Kondo, Motohiko
• Editors: Beckles, Diane
• Is Part Of: Journal of experimental botany. Volume 72:Number 7(2021)
• Page Start: 2570
• Page End: 2583
• Publication Date: 2021-01-22
• Subjects: ADP-glucose pyrophosphorylase -- grain filling -- high-yielding -- rice -- Oryza sativa -- sink activity -- sink strength -- 13C labelling -- starch synthesis; Botany -- Periodicals; Botany, Experimental -- Periodicals; Plant physiology -- Periodicals; 580
• DOI: 10.1093/jxb/erab016
• Languages: English
• ISSNs: 0022-0957

Abstract

Abstract : Carbon-flow analysis at the metabolite level reveals that relatively slow starch synthesis from hexose is the primary metabolic reason for low sink activity in the high-yielding rice cultivar 'Momiroman'. Abstract: 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 13 C. 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.