Evolution and Functional Divergence of the Fructokinase Gene Family in Populus.

Weijie Xu,Sisi Chen,Deqiang Zhang,Yiyang Zhao,Jianbo Xie

doi:10.3389/fpls.2020.00484

Abstract

New kinase has emerged throughout evolution, but how new kinase evolve while maintaining their functions and acquiring new functions remains unclear. Fructokinase (FRK), the gateway kinase to fructose metabolism, plays essential roles in plant development, and stress tolerance. Here, we explored the evolution of FRK gene family in 20 plant species (from green algae to angiosperms) and their functional roles in Populus. We identified 125 putative FRK genes in the 20 plant species with an average of 6 members per species. Phylogenetic analysis separated these 125 genes into 8 clades including 3 conserved clades and 5 specific clades, the 5 of which only exist in green algae or angiosperms. Evolutionary analysis revealed that FRK genes in ancient land plants have the largest number of functional domains with the longest amino acid sequences, and the length of FRK genes became shorter during the transition to vascular plants. This was accompanied by loss, acquisition, and diversification of functional domains. In Populus, segmental duplication appears to be the main mechanism for the expansion of FRK genes. Specially, most FRK genes duplicated in salicoids are regulated by Populus-specific microRNAs. Furthermore, compared with common FRKs, Populus-specific FRKs have showed higher expression specificity and are associated with fewer growth and wood property traits, which suggests that these FRKs may have undergone functional divergence. Our study explores the specific roles of FRKs in the Populus genome and provides new insights for functional investigation of this gene family.

Highlights

Evolution is accompanied by various changes including morphological, physiological and genome, which allow organisms to deal with challenging conditions, including increased CO2 concentration, desiccation, changes in light intensity, high temperature, marked seasonal changes, and limited nutrient availability (Delaux et al, 2012; Romani et al, 2018)
We mainly focused on the evolution and functional divergence of the FRK gene family and the generation of functional novelty of new FRK gene
To perform a comprehensive analysis of FRK gene family in plant species, we firstly performed an analysis of phylogeny on the FRK genes of 20 plant species (Phytozome.v11.0, see text footnote 9), including six chlorophytes: C. reinhardtii, D. salina, V. carteri, C. subellipsoidea, M. pusill and Micromonas sp

Summary

Introduction

Evolution is accompanied by various changes including morphological, physiological and genome, which allow organisms to deal with challenging conditions, including increased CO2 concentration, desiccation, changes in light intensity, high temperature, marked seasonal changes, and limited nutrient availability (Delaux et al, 2012; Romani et al, 2018). Changes of Fructokinase Gene Family in Populus these physiological are regulated by kinase, which are major drivers of evolution (Michelson et al, 1985; Mehlgarten et al, 2018). As an important kinase to catalyze the key metabolic step of fructose phosphorylation, fructokinase (FRK) helps phosphorylates fructose to form fructose 6-phosphate (F6P) and functions in all stages of plant development (Plaxton, 1996). The FRK gene family is characterized by the presence of a phosphofructokinase-B (PfkB) domain and exists in all living organism. The PfkB domain possesses two notable motifs: a di-GLY (GG) motif in the N-terminal region and a GXGD or AXGD motif in the C-terminal region (Mcmahan et al, 1997; Kuettel et al, 2011). The aspartate in the GXGD or AXGD motif acts as a factor during catalysis, and it activates the C6 fructose hydroxyl group for nucleophilic attack on the γ-phosphate in ATP; the GG motif which connects the lid supplies flexibility in the hinge region (Riggs et al, 2017)

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Discussion

Conclusion