Phosphorylation of ADP-Glucose Pyrophosphorylase During Wheat Seeds Development.

Danisa M L Ferrero,Claudia V Piattoni,Bruno E Rojas,Matías D Hartman,Miguel A Ballicora,Alberto A Iglesias,Matías D Asencion Diez

doi:10.3389/fpls.2020.01058

Danisa M L Ferrero, Claudia V Piattoni + Show 5 more

Open Access

https://doi.org/10.3389/fpls.2020.01058

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Abstract

Starch is the dominant reserve polysaccharide accumulated in the seed of grasses (like wheat). It is the most common carbohydrate in the human diet and a material applied to the bioplastics and biofuels industry. Hence, the complete understanding of starch metabolism is critical to design rational strategies to improve its allocation in plant reserve tissues. ADP-glucose pyrophosphorylase (ADP-Glc PPase) catalyzes the key (regulated) step in the synthetic starch pathway. The enzyme comprises a small (S) and a large (L) subunit forming an S2L2 heterotetramer, which is allosterically regulated by orthophosphate, fructose-6P, and 3P-glycerate. ADP-Glc PPase was found in a phosphorylated state in extracts from wheat seeds. The amount of the phosphorylated protein increased along with the development of the seed and correlated with relative increases of the enzyme activity and starch content. Conversely, this post-translational modification was absent in seeds from Ricinus communis. In vitro, the recombinant ADP-Glc PPase from wheat endosperm was phosphorylated by wheat seed extracts as well as by recombinant Ca2+-dependent plant protein kinases. Further analysis showed that the preferential phosphorylation takes place on the L subunit. Results suggest that the ADP-Glc PPase is a phosphorylation target in seeds from grasses but not from oleaginous plants. Accompanying seed maturation and starch accumulation, a combined regulation of ADP-Glc PPase by metabolites and phosphorylation may provide an enzyme with stable levels of activity. Such concerted modulation would drive carbon skeletons to the synthesis of starch for its long-term storage, which later support seed germination.

Highlights

Baguette 11 samples collected at 3, 6, 10, 14, 17, and 27 days post-anthesis (DPA), and spikes were frozen immediately in liquid nitrogen. This sampling was based on reports indicating that the complete growth of wheat seeds is reached at 45 DPA, establishing the following respective phases of development: cell proliferation 0–10 DPA, accumulation or reserves 11–30 DPA, and seed maturation and desiccation 30–45 DPA
To better understand starch biosynthesis in seeds, we explored about contents of the polysaccharide and TAGs, as well as ADP-Glc PPase activity and phosphorylation profiles along with the development of Triticum aestivum seeds (Table 1 and Figure 1)
We report that wheat seed ADP-Glc PPase undergoes progressive phosphorylation along with grain development

Summary

Introduction

Starch is a major product of photosynthesis performed by vascular plants and constitutes the foremost storage of carbon and energy in grasses (Jeon et al, 2010; Pandey et al, 2012; Tuncel and Okita, 2013; MacNeill et al, 2017; Goren et al, 2018). Improvement (in quantity and quality) in the production of key harvestable grains is a challenge to be solved in the coming decades It is projected a critical demographic expansion together with increasing industrial requirements of feedstock for biofuels, bioplastics, and bioadhesives to cope with climate change by the mid-century (Morell and Myers, 2005; Godfray et al, 2010; Tuncel and Okita, 2013; Iglesias, 2015; Goren et al, 2018). The in-depth understanding of the process of starch biosynthesis is relevant to better design strategies to increase yields in plants of agronomic interest

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