Kinetic Modeling of Sunflower Grain Filling and Fatty Acid Biosynthesis.

Ignacio Durruty,Luis A N Aguirrezábal,María M Echarte

doi:10.3389/fpls.2016.00586

Abstract

Grain growth and oil biosynthesis are complex processes that involve various enzymes placed in different sub-cellular compartments of the grain. In order to understand the mechanisms controlling grain weight and composition, we need mathematical models capable of simulating the dynamic behavior of the main components of the grain during the grain filling stage. In this paper, we present a non-structured mechanistic kinetic model developed for sunflower grains. The model was first calibrated for sunflower hybrid ACA855. The calibrated model was able to predict the theoretical amount of carbohydrate equivalents allocated to the grain, grain growth and the dynamics of the oil and non-oil fraction, while considering maintenance requirements and leaf senescence. Incorporating into the model the serial-parallel nature of fatty acid biosynthesis permitted a good representation of the kinetics of palmitic, stearic, oleic, and linoleic acids production. A sensitivity analysis showed that the relative influence of input parameters changed along grain development. Grain growth was mostly affected by the specific growth parameter (μ′) while fatty acid composition strongly depended on their own maximum specific rate parameters. The model was successfully applied to two additional hybrids (MG2 and DK3820). The proposed model can be the first building block toward the development of a more sophisticated model, capable of predicting the effects of environmental conditions on grain weight and composition, in a comprehensive and quantitative way.

Highlights

The weight and composition of oilseed grains at harvest are complex traits that depend on the dynamics of many processes occurring earlier at both the plant and organ levels
Most of the photoassimilates supplied to the sunflower grains during their filling period are contemporaneously synthesized by the leaves and leaves are considered the main source of substrate for grain growth (Hall et al, 1990; López Pereira et al, 2008; Echarte et al, 2012)
Since grains are the main sink of photoassimilates during this period, changes in assimilate production at Sunflower Kinetic Modeling the source can be interpreted as changes in carbon availability in the developing grains (Hall et al, 1995), sucrose being the major carbohydrate and the main phloem-transported sugar in sunflower plants (Alkio et al, 2002)

Summary

Introduction

The weight and composition of oilseed grains at harvest are complex traits that depend on the dynamics of many processes occurring earlier at both the plant and organ levels. Their response to the genotype and the environment results from several linked processes controlled at different levels of organization, from sub-cellular to crop (Martre et al, 2011). The sensitivity of these traits to multiple factors changes during grain development (Aguirrezábal et al, 2003; Rondanini et al, 2003; Echarte et al, 2013). Part of this carbon is directed to the pool of acetyl-CoA, the precursor of fatty acids, which are the main components of sunflower oil

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