Effects of High Temperature on the Fine Structure of Starch During the Grain-filling Stages in Rice: Mathematical Modeling and Integrated Enzymatic Analysis

Background: High temperature during the grain-filling stage is an important factor that can affect grain quality by altering the composition and structure of starch in rice. Therefore, it is important to study the regulatory mechanism of high temperature on rice starch biosynthesis.

Results: Two japonica cultivars, the waxy rice Taihunuo and non-waxy Nangeng 5055 were used to examine the effect of high temperature on the fine structure of starch during the grain-filling stage. Analysis of starch chain length distribution indicated that exposure to a high temperature increased the content of starch with medium-long chains and decreased the starch with short chains in both rice varieties. The differences of amylopectin synthesis responding to high temperature between waxy and non-waxy rice can shed light on the interactions of amylose and amylopectin synthesis under high temperature conditions. In the non-waxy variety, the amylose biosynthesis may affect the short and medium-long amylopectin biosynthesis under high temperature. A mathematical fitting model was used to interpret the fine structure of amylopectin and a series of parameters with enzymatical significance (β and γ) were obtained. The fitting results showed that the waxy and non-waxy rice had similar responses to high temperature. The variations of the parameter response to high temperature was more remarkable in Taihunuo. Activity analysis of starch synthesis-related enzymes during the grain-filling stage demonstrated the reliability of model fitting results.

Conclusion: The influences of high temperature on the fine structure of starch are similar between waxy and non-waxy rice. Amylose biosynthesis may affect amylopectin biosynthesis under high temperature. © 2018 Society of Chemical Industry.