Phaseolus vulgaris SUT1.1 is a high affinity sucrose-proton co-transporter

James P. Santiago, John M. Ward, Thomas D. Sharkey

Research output: Contribution to journalArticlepeer-review


Plant sucrose transporters are required for phloem loading, and therefore are essential for plant growth and development. In common beans (Phaseolus vulgaris) there are only two sucrose transporters functionally characterized. Through a previous RNA-seq study, we identified a putative sucrose transporter in common bean, which we hypothesize to function in import of sucrose into plant cells. In silico analysis revealed that PvSUT1.1 is a putative sucrose-proton co-transporter distinct from other characterized sucrose transporters in common bean indicating that this is a previously undescribed transporter protein in beans. Further analysis revealed that PvSUT1.1 shares high protein sequence homology to the phloem loader Arabidopsis SUC2; both have 12 transmembrane domains, a typical characteristic of plant sucrose transporters. Heterologous expression in yeast further showed PvSUT1.1 to be functional and it imported sucrose into yeast cells with a Km of 0.7 mM sucrose. Import of sucrose through PvSUT1.1 is also pH-dependent with highest uptake at pH 4.0, and activity is lost in the presence of the uncoupler carbonyl cyanide 3-chlorophenylhydrazone. Consistent with identification of PvSUT1.1 as a Type I transporter, PvSUT1.1 also transports esculin. Finally, PvSUT1.1 showed expression in multiple tissues and the protein was localized to the plasma membrane. The results show that PvSUT1.1 is a sucrose transporter that is probably involved in the uptake of sucrose into source and sink cells. The potential role of PvSUT1.1 in leaf phloem loading of sucrose in common beans and its importance in heat tolerance of reproductive tissues are further discussed.

Original languageEnglish (US)
Article numbere00260
JournalPlant Direct
Issue number8
StatePublished - Aug 1 2020

Bibliographical note

Funding Information:
The authors thank Professor Mechthild Tegeder (Washington State University) for providing the construct for plasma membrane control AtPIP2A that was used for the localization experiment in this study. The authors thank Dr. Sarathi Weraduwage (Michigan State University) for proofreading the manuscript and providing constructive comments. Finally, the authors thank the MSU Plant Resilience Institute for funding this project and Michigan AgBioResearch for partial salary support for TDS.


  • Esculin uptake
  • phloem loading
  • sucrose transporter
  • sucrose uptake
  • transporter regulation
  • uptake kinetics

PubMed: MeSH publication types

  • Journal Article

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