Differential Evolution of α-Glucan Water Dikinase (GWD) in Plants.

Muyiwa S Adegbaju,Bolaji N Thomas,Olanrewaju B Morenikeji,André O Hudson,Eli J Borrego

doi:10.3390/plants9091101

Muyiwa S Adegbaju, Bolaji N Thomas + Show 3 more

Open Access

https://doi.org/10.3390/plants9091101

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Abstract

The alpha-glucan water dikinase (GWD) enzyme catalyzes starch phosphorylation, an integral step in transitory starch degradation. The high phosphate content in stored starch has great industrial value, due to its physio–chemical properties making it more versatile, although the phosphate content of stored starch varies depending on the botanical source. In this study, we used various computational approaches to gain insights into the evolution of the GWD protein in 48 plant species with possible roles in enzyme function and alteration of phosphate content in their stored starch. Our analyses identified deleterious mutations, particularly in the highly conserved 5 aromatic amino acid residues in the dual tandem carbohydrate binding modules (CBM-45) of GWD protein in C. zofingiensis, G. hirsutum, A. protothecoides, P. miliaceum, and C. reinhardtii. These findings will inform experimental designs for simultaneous repression of genes coding for GWD and the predicted interacting proteins to elucidate the role this enzyme plays in starch degradation. Our results reveal significant diversity in the evolution of GWD enzyme across plant species, which may be evolutionarily advantageous according to the varying needs for phosphorylated stored starch between plants and environments.

Highlights

The plastid-localized alpha-glucan water dikinase (GWD) gene is encoded by the nuclear genome and its products catalyzes reactions responsible for starch phosphorylation, an essential step in the de novo biosynthesis of this polysaccharide [1]
Our result showed that GWD enzyme in rhodophytes (P. umbilicalis and C. crispus) was most distant from the rest of plant phyla, forming an out-group (Figure 1)
We used various computational approaches to compare the GWD sequences of 48 plant species, with our results providing an insight into the evolutionary variation in GWD catalytic activity among plants

Summary

Introduction

The plastid-localized alpha-glucan water dikinase (GWD) gene is encoded by the nuclear genome and its products catalyzes reactions responsible for starch phosphorylation, an essential step in the de novo biosynthesis of this polysaccharide [1]. (EC 2.7.9.4) and phosphoglucan water dikinase (PWD) or GWD3 (PWD; EC 2.7.9.5) have been identified in most plants [2]. The dikinase mechanism of GWD and PWD involve autophosphorylation of the catalytic histidine by the β-phosphate of ATP, and the transfer of β-phosphate from the stable phosphohistidine to either the C3 or C6 position of the glucosyl residue of starch, while the γ-phosphate is transferred to water [1,3]. Glucosyl residues in its C6 positions are phosphorylated by GWD1 [4].

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Discussion

Conclusion