AUTHOR=Geng Yanqiu , Wu Mengjia , Zhang Chunmei 

TITLE=Sugar Transporter ZjSWEET2.2 Mediates Sugar Loading in Leaves of Ziziphus jujuba Mill

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.01081

DOI=10.3389/fpls.2020.01081

ISSN=1664-462X

ABSTRACT=<p>In plants, sugar transporters play an important role in the allocation of sugars from cells in source organs to cells in sink organs. Hence, an understanding of the molecular basis and regulation of assimilate partitioning by sugar transporters is essential. Leaves are the main source of photosynthetic products. In jujube (<italic>Ziziphus jujuba</italic> Mill.), the mechanisms regulating initial sugar unloading in leaves are still unclear. In this study, an expression profiling analysis showed that <italic>ZjSWEET2.2</italic>, encoding a sugar transporter in the SWEET family, is highly expressed in leaves. Over-expression of <italic>ZjSWEET2.2</italic> increased carbon fixation in photosynthetic organs. Our analyses showed that <italic>ZjSWEET2.2</italic> encodes a plasma membrane-localized sugar transporter protein. Its expression levels were found to be suppressed under drought stress and by high concentrations of exogenous sugars, but increased by low concentrations of exogenous sugars. Finally, DNA sequence analyses revealed several <italic>cis</italic>-elements related to sugar signaling in the promoter of <italic>ZjSWEET2.2</italic>. Together, these results suggest that ZjSWEET2.2 functions to mediate photosynthesis by exporting sugars from photosynthetic cells in the leaves, and its gene expression is regulated by sugar signals.</p>