The evolutionary history of the sucrose synthase gene family in higher plants

Xiaoyang Xu,Ting Zhang,Haiyan Yuan,Menglan Hou,Chunxiao Liu,Suzhen Huang,Yongheng Yang,Yuming Sun

doi:10.1186/s12870-019-2181-4

Xiaoyang Xu, Ting Zhang + Show 6 more

Open Access

https://doi.org/10.1186/s12870-019-2181-4

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Abstract

BackgroundSucrose synthase (SUS) is widely considered a key enzyme participating in sucrose metabolism in higher plants and regarded as a biochemical marker for sink strength in crops. However, despite significant progress in characterizing the physiological functions of the SUS gene family, knowledge of the trajectory of evolutionary processes and significance of the family in higher plants remains incomplete.ResultsIn this study, we identified over 100 SUS genes in 19 plant species and reconstructed their phylogenies, presenting a potential framework of SUS gene family evolution in higher plants. Three anciently diverged SUS gene subfamilies (SUS I, II and III) were distinguished based on their phylogenetic relationships and unique intron/exon structures in angiosperms, and they were found to have evolved independently in monocots and dicots. Each subfamily of SUS genes exhibited distinct expression patterns in a wide range of plants, implying that their functional differentiation occurred before the divergence of monocots and dicots. Furthermore, SUS III genes evolved under relaxed purifying selection in dicots and displayed narrowed expression profiles. In addition, for all three subfamilies of SUS genes, the GT-B domain was more conserved than the “regulatory” domain.ConclusionsThe present study reveals the evolution of the SUS gene family in higher plants and provides new insights into the evolutionary conservation and functional divergence of angiosperm SUS genes.

Highlights

Sucrose synthase (SUS) is widely considered a key enzyme participating in sucrose metabolism in higher plants and regarded as a biochemical marker for sink strength in crops
These results will provide a fundamental reference for understanding the evolutionary history of SUS genes and how evolutionary divergence contributes to the functional diversity of SUS genes
Classification of SUS genes in angiosperms A total of 96 SUS genes were identified in 16 angiosperm species including 10 dicot plants, 5 monocot plants and a basal angiosperm, Amborella trichopoda, using a hidden Markov model (HMM) and BLASTP searches (Fig. 1)

Summary

Introduction

Sucrose synthase (SUS) is widely considered a key enzyme participating in sucrose metabolism in higher plants and regarded as a biochemical marker for sink strength in crops. Despite significant progress in characterizing the physiological functions of the SUS gene family, knowledge of the trajectory of evolutionary processes and significance of the family in higher plants remains incomplete. Sucrose catabolism in plants is one of the largest metabolic fluxes in the world, and it plays critical roles in carbon resource allocation and sugar signalling initiation [1, 2]. There is compelling evidence for the role of SUS in facilitating the entry of carbon into the metabolism of nonphotosynthetic plant cells and in determining sink strength in crop species. SUS is encoded by a small multigene family in the higher plants examined to date.

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Discussion

Conclusion