Integrative View of the Diversity and Evolution of SWEET and SemiSWEET Sugar Transporters

Frontiers in Plant Science

Yu Xi Duan¹  Xiao Feng Zhu¹  Yuan Hu Xuan¹  Baolei Jia²  Che Ok Jeon²  Li-Qing Chen³  Lu Jiang Hao⁴  Jie Zhang⁴  Zhong Ji Pu⁵ 

[1] College of Plant Protection, Shenyang Agricultural University, Shenyang, China;Department of Life Sciences, Chung-Ang University, Seoul, South Korea;Department of Plant Biology, University of Illinois at Urbana–Champaign, Urbana, IL, United States;School of Bioengineering, Qilu University of Technology, Jinan, China;School of Life Science and Biotechnology, Dalian University of Technology, Dalian, China;

关键词: SWEET;    SemiSWEET;    evolution;    sequence similarity network;    gene fusion;    biosphere;   

DOI  :  10.3389/fpls.2017.02178

来源: DOAJ

【 摘 要 】

Sugars Will Eventually be Exported Transporter (SWEET) and SemiSWEET are recently characterized families of sugar transporters in eukaryotes and prokaryotes, respectively. SemiSWEETs contain 3 transmembrane helices (TMHs), while SWEETs contain 7. Here, we performed sequence-based comprehensive analyses for SWEETs and SemiSWEETs across the biosphere. In total, 3,249 proteins were identified and ≈60% proteins were found in green plants and Oomycota, which include a number of important plant pathogens. Protein sequence similarity networks indicate that proteins from different organisms are significantly clustered. Of note, SemiSWEETs with 3 or 4 TMHs that may fuse to SWEET were identified in plant genomes. 7-TMH SWEETs were found in bacteria, implying that SemiSWEET can be fused directly in prokaryote. 15-TMH extraSWEET and 25-TMH superSWEET were also observed in wild rice and oomycetes, respectively. The transporters can be classified into 4, 2, 2, and 2 clades in plants, Metazoa, unicellular eukaryotes, and prokaryotes, respectively. The consensus and coevolution of amino acids in SWEETs were identified by multiple sequence alignments. The functions of the highly conserved residues were analyzed by molecular dynamics analysis. The 19 most highly conserved residues in the SWEETs were further confirmed by point mutagenesis using SWEET1 from Arabidopsis thaliana. The results proved that the conserved residues located in the extrafacial gate (Y57, G58, G131, and P191), the substrate binding pocket (N73, N192, and W176), and the intrafacial gate (P43, Y83, F87, P145, M161, P162, and Q202) play important roles for substrate recognition and transport processes. Taken together, our analyses provide a foundation for understanding the diversity, classification, and evolution of SWEETs and SemiSWEETs using large-scale sequence analysis and further show that gene duplication and gene fusion are important factors driving the evolution of SWEETs.

【 授权许可】

Unknown