Sucrose transporter2 contributes to maize growth, development, and crop yield

• Published in: Journal of integrative plant biology 2017-06, Vol.59 (6), p.390-408
• Main Authors: Leach, Kristen A., Tran, Thu M., Slewinski, Thomas L., Meeley, Robert B., Braun, David M.
• Format: Article
• Language: English
• Subjects: Abundance; Agronomy; Biomass; Carbohydrate Metabolism; Corn; Crop yield; Daylight; Diurnal; Fluorescence; Fructose; Gene expression; Homology; Kernels; Leaves; Localization; Membrane Transport Proteins - genetics; Membrane Transport Proteins - metabolism; Mesophyll; Metabolism; Mutants; Mutation; Night; Photosynthates; Plant Development; Plant Leaves - metabolism; Plant Proteins - genetics; Plant Proteins - metabolism; Plants; Plants (botany); Protein transport; Proteins; Protoplasts; Red fluorescent protein; Siblings; Starch; Stress, Physiological; Sucrose; Sucrose - metabolism; Sucrose transporter; Sugar; Tissues; Transcription; Zea mays; Zea mays - genetics; Zea mays - growth & development; Zea mays - metabolism
• ISSN: 1672-9072; 1744-7909
• DOI: 10.1111/jipb.12527

During daylight, plants produce excess photosynthates, including sucrose, which is temporarily stored in the vacuole. At night, plants remobilize sucrose to sustain metabolism and growth. Based on homology to other sucrose transporter (SUT) proteins, we hypothesized the maize (Zea mays) SUCROSE TRANSPORTER2 (ZmSUT2) protein functions as a sucrose/H+ symporter on the vacuolar membrane to export transiently stored sucrose. To understand the biological role of ZmSut2, we examined its spatial and temporal gene expression, determined the protein subcellular localization, and characterized loss‐of‐function mutations. ZmSut2 mRNA was ubiquitously expressed and exhibited diurnal cycling in transcript abundance. Expressing a translational fusion of ZmSUT2 fused to a red fluorescent protein in maize mesophyll cell protoplasts revealed that the protein localized to the tonoplast. Under field conditions, zmsut2 mutant plants grew slower, possessed smaller tassels and ears, and produced fewer kernels when compared to wild‐type siblings. zmsut2 mutants also accumulated two‐fold more sucrose, glucose, and fructose as well as starch in source leaves compared to wild type. These findings suggest (i) ZmSUT2 functions to remobilize sucrose out of the vacuole for subsequent use in growing tissues; and (ii) its function provides an important contribution to maize development and agronomic yield. In this study, the role of ZmSUT2, a maize vacuolar sucrose transport system, in carbon partitioning and crop yield is demonstrated. During the day, plants transiently store excess sucrose in vacuoles. Assays show that ZmSUT2 functions in sucrose export from the vacuole into the cytoplasm. Mutant maize plants lacking ZmSut2 have reduced growth, accumulate sugars and starch in their leaves, and have reduced crop yield.