Sucrose transporter ZmSut1 expression and localization uncover new insights into sucrose phloem loading

Baker, R. F., Leach, K. A., Boyer, N. R., Swyers, M. J., Benitez-Alfonso, Y., Skopelitis, T., Luo, A., Sylvester, A., Jackson, D., Braun, D. M. (November 2016) Sucrose transporter ZmSut1 expression and localization uncover new insights into sucrose phloem loading. Plant Physiol, 172 (3). pp. 1876-1898. ISSN 1532-2548 (Electronic)0032-0889 (Linking)

URL: http://www.ncbi.nlm.nih.gov/pubmed/27621426
DOI: 10.1104/pp.16.00884

Abstract

Sucrose (Suc) transporters (SUTs) translocate Suc across cellular membranes, and, in eudicots, multiple SUTs are known to function in Suc phloem loading in leaves. In maize (Zea mays L.), the Sucrose transporter1 (ZmSut1) gene has been implicated in Suc phloem loading based upon RNA expression in leaves, electrophysiological experiments, and phenotypic analysis of zmsut1 mutant plants. However, no previous studies have examined the cellular expression of ZmSut1 RNA or subcellular localization of the ZmSUT1 protein to assess the gene's hypothesized function in Suc phloem loading or to evaluate its potential roles, such as phloem unloading, in non-photosynthetic tissues. To this end, we performed RNA in situ hybridization experiments, promoter: reporter gene analyses, and ZmSUT1 localization studies to elucidate the cellular expression pattern of the ZmSut1 transcript and protein. These data showed ZmSut1 was expressed in multiple cell types throughout the plant, and indicated it functions in phloem companion cells to load Suc, and also in other cell types to retrieve Suc from the apoplasm to prevent its accumulation and loss to the transpiration stream. Additionally, by comparing a phloem-mobile tracer with ZmSut1 expression, we determined that developing maize leaves dynamically switch from symplasmic to apoplasmic phloem unloading, reconciling previously conflicting reports, and suggest that ZmSut1 does not have an apparent function in either unloading process. A model for the dual roles for ZmSut1 function (phloem loading and apoplasmic recycling), Sut1 evolution, and its possible use to enhance Suc export from leaves in engineering C3 grasses for C4 photosynthesis is discussed.

Item Type: Paper
Subjects: organism description > plant > maize
bioinformatics > genomics and proteomics > genetics & nucleic acid processing > DNA, RNA structure, function, modification > RNA expression
CSHL Authors:
Communities: CSHL labs > Jackson lab
Depositing User: Matt Covey
Date: November 2016
Date Deposited: 23 Sep 2016 15:32
Last Modified: 11 Jan 2017 16:57
PMCID: PMC5100798
Related URLs:
URI: http://repository.cshl.edu/id/eprint/33534

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