SlSWEET1a is involved in glucose import to young leaves in tomato plants

Li Hsuan Ho, Patrick A.W. Klemens, H. Ekkehard Neuhaus, Han Yu Ko, Shu Ying Hsieh, Woei Jiun Guo

Research output: Contribution to journalArticlepeer-review

7 Citations (Scopus)


Sugar allocation from source to sink (young) leaves, critical for plant development, relies on activities of plasma membrane sugar transporters. However, the key sugar unloading mechanism to sink leaves remains elusive. SWEET transporters mediate sugar efflux into reproductive sinks; therefore, they are promising candidates for sugar unloading during leaf growth. Transcripts of SlSWEET1a, belonging to clade I of the SWEET family, were markedly more abundant than those of all other 30 SlSWEET genes in young leaves of tomatoes. High expression of SlSWEET1a was also detected in reproductive sinks, such as flowers. SlSWEET1a was dominantly expressed in leaf unloading veins, and the green fluorescent protein (GFP) fusion protein was localized to the plasma membrane using Arabidopsis protoplasts, further implicating this carrier in sugar unloading. In addition, yeast growth assays and radiotracer uptake analyses further demonstrated that SlSWEET1a acted as a low-affinity (Km ∼100 mM) glucose-specific carrier with a passive diffusion manner. Finally, virus-induced gene silencing of SlSWEET1a expression reduced hexose accumulation to ∼50% in young leaves, with a parallel 2-fold increase in mature leaves. Thus, we propose a novel function for SlSWEET1a in the uptake of glucose into unloading cells as part of the sugar unloading mechanism in sink leaves of tomato.

Original languageEnglish
Pages (from-to)3241-3254
Number of pages14
JournalJournal of experimental botany
Issue number12
Publication statusPublished - 2019 Jun

All Science Journal Classification (ASJC) codes

  • Physiology
  • Plant Science

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