scholarly journals Genetic Control of Carbon Partitioning in Grasses: Roles of Sucrose Transporters and Tie-dyed Loci in Phloem Loading

2009 ◽  
Vol 149 (1) ◽  
pp. 71-81 ◽  
Author(s):  
David M. Braun ◽  
Thomas L. Slewinski
Keyword(s):  
Genetic Control ◽  
Phloem Loading ◽  
Carbon Partitioning ◽  
Sucrose Transporters

scholarly journals Regulation of Sucrose Transporters and Phloem Loading in Response to Environmental Cues

2017 ◽  
Vol 176 (1) ◽  
pp. 930-945 ◽  
Author(s):  
Qiyu Xu ◽  
Siyuan Chen ◽  
Ren Yunjuan ◽  
Shaolin Chen ◽  
Johannes Liesche
Keyword(s):  
Phloem Loading ◽  
Environmental Cues ◽  
Sucrose Transporters

scholarly journals Carbon export from leaves is controlled via ubiquitination and phosphorylation of sucrose transporter SUC2

2020 ◽  
Vol 117 (11) ◽  
pp. 6223-6230 ◽  
Author(s):  
Qiyu Xu ◽  
Shijiao Yin ◽  
Yue Ma ◽  
Min Song ◽  
Yingjie Song ◽  
...  
Keyword(s):  
Vascular Tissue ◽  
Carbon Sink ◽  
Phloem Loading ◽  
Sucrose Transporter ◽  
Dependent Manner ◽  
Carbon Export ◽  
Sucrose Transporters ◽  
Ubiquitin Conjugating Enzyme

All multicellular organisms keep a balance between sink and source activities by controlling nutrient transport at strategic positions. In most plants, photosynthetically produced sucrose is the predominant carbon and energy source, whose transport from leaves to carbon sink organs depends on sucrose transporters. In the model plantArabidopsis thaliana, transport of sucrose into the phloem vascular tissue by SUCROSE TRANSPORTER 2 (SUC2) sets the rate of carbon export from source leaves, just like the SUC2 homologs of most crop plants. Despite their importance, little is known about the proteins that regulate these sucrose transporters. Here, identification and characterization of SUC2-interaction partners revealed that SUC2 activity is regulated via its protein turnover rate and phosphorylation state. UBIQUITIN-CONJUGATING ENZYME 34 (UBC34) was found to trigger turnover of SUC2 in a light-dependent manner. The E2 enzyme UBC34 could ubiquitinate SUC2 in vitro, a function generally associated with E3 ubiquitin ligases.ubc34mutants showed increased phloem loading, as well as increased biomass and yield. In contrast, mutants of another SUC2-interaction partner, WALL-ASSOCIATED KINASE LIKE 8 (WAKL8), showed decreased phloem loading and growth. An in vivo assay based on a fluorescent sucrose analog confirmed that SUC2 phosphorylation by WAKL8 can increase transport activity. Both proteins are required for the up-regulation of phloem loading in response to increased light intensity. The molecular mechanism of SUC2 regulation elucidated here provides promising targets for the biotechnological enhancement of source strength.

scholarly journals Elucidation of the genetic control of carbohydrate partitioning in Zea mays

2019 ◽  
Author(s):  
◽  
Benjamin Thomas Julius
Keyword(s):  
Zea Mays ◽  
Genetic Control ◽  
Stress Responses ◽  
Leaf Tissue ◽  
Phloem Loading ◽  
Primary Cell Wall ◽  
Future Research ◽  
Crystalline Cellulose ◽  
Carbohydrate Partitioning ◽  
Transporter Family

Carbohydrate partitioning, the process of transporting carbohydrates from sites of synthesis in hotosynthetic tissue to developing sink tissues, is crucial for the growth, development, and yield in plants and crops. Anatomical, physiological, and biochemical studies have shed light on this process; however, there is not much known in regards to the genetic control of carbohydrate partitioning. The work described here uses forward and reverse genetic methods to further elucidate the genetic control of carbohydrate partitioning in Zea mays (maize). Chapter 1 reviews what is currently known regarding the function of sugar transporters in the phloem loading and unloading pathways. Additionally, the importance and role of carbohydrate partitioning during abiotic and biotic stress responses is discussed. Chapters 2-4 describe the characterization and cloning of the allelic recessive mutants carbohydrate partitioning defective28 (cpd28) and carbohydrate partitioning defective47 (cpd47) (Chapter 2) and the semi-dominant gain-of-function mutant Carbohydrate partitioning defective1 (Cpd1) (Chapters 3 and 4). All three mutant's hyper-accumulate carbohydrates in their mature leaves due to decreased sucrose export. The cpd28 and cpd47 mutations decrease the amount of crystalline cellulose and likely impair primary cell wall development. The Cpd1 mutation results in the unregulated deposition of the callose in the phloem of leaf and root tissue. Chapter 5 summarizes the Sugars Will Eventually Exit Tissue (SWEET) transporter family and their function across a number of plant species. In this review I was responsible for the generation of a 15 angiosperm protein phylogenetic analysis describing the relationship and structure found in the transporter family. Chapter 6 builds upon the phylogentic study performed in Chapter 5 and identifies and characterizes the function of the SWEET13a, SWEET13b, and WEET13c transporters in the phloem loading pathway in maize utilizing CRISPR/Cas9 mutagenesis. Chapter 7 summarizes the discoveries made in the previous chapters, their contribution to the field, and discusses future research directions. Appendix A describes a protocol I optimized for the fixation, embedding, sectioning, Laser Capture Microdissection, and RNA-sequencing of desired cell groups in mature maize leaf tissue. Appendix B describes the characterization and cloning of the recessive mutant carbohydrate partitioning defective33 (cpd33) and its role in plasmodesmatal function. I contributed to the cloning of cpd33. Appendix C analyzes the expression levels and potential roles of SWEET and TST transporters in sweet and grain sorghum. I was responsible for the expression analysis of the SWEET genes discussed in this publication.

scholarly journals Impaired phloem loading in genome-edited triple knock-out mutants of SWEET13 sucrose transporters

2017 ◽  
Author(s):  
Margot Bezrutczyk ◽  
Thomas Hartwig ◽  
Marc Horschman ◽  
Si Nian Char ◽  
Jinliang Yang ◽  
...  
Keyword(s):  
Zea Mays ◽  
Crop Yield ◽  
Zea Mays L ◽  
Carbon Allocation ◽  
Soluble Sugars ◽  
Photosynthetic Apparatus ◽  
Phloem Loading ◽  
Leaf Angle ◽  
Knock Out ◽  
Sucrose Transporters

Crop yield depends on efficient allocation of sucrose from leaves to seeds. In Arabidopsis, phloem loading is mediated by a combination of SWEET sucrose effluxers and subsequent uptake by SUT1/SUC2 sucrose/H+ symporters. ZmSUT1 is essential for carbon allocation in maize, but the relative contribution to apoplasmic phloem loading and retrieval of sucrose leaking from the translocation path is not known. We therefor tested whether SWEETs are important for phloem loading in maize. Here we identified three leaf-expressed SWEET sucrose transporters as key components of apoplasmic phloem loading in Zea mays L. Notably, ZmSWEET13 paralogs (a, b, c) are among the highest expressed genes in the leaf vasculature. Genome-edited triple knock-out mutants are severely stunted. Photosynthesis of mutants was impaired and leaves accumulated starch and soluble sugars. RNA-seq revealed profound transcriptional deregulation of genes associated with the photosynthetic apparatus and carbohydrate metabolism. GWAS analyses may indicate that variability in ZmSWEET13s is correlated with agronomical traits, specifically flowering time and leaf angle. This work provides support for cooperation of three ZmSWEET13s with ZmSUT1 in phloem loading in Zea mays L. Our study highlights these three ZmSWEET13 sucrose transporters as possible candidates for the engineering of crop yield.

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