Functional Analysis of Plant Sucrose Transporters
The goal of this project is to develop a fundamental understanding of the mechanisms used by plants to transport organic carbon and nitrogen through phloem (vascular tissue). Sucrose transporters (SUTs) and amino acid transporters (AAPs) function in phloem loading in source leaves and in uptake into cells of sink tissue (such as seeds, roots and other non-photosynthetic tissues). Ammonium transporters (AMTs) function in ammonium uptake from soil and are critical for supplying N for amino acid synthesis. SUTs, AAPs and AMTs all are encoded by small gene families in plants and these transporters function at critical points in the long-distance transport pathway. This project uses the following approaches to measure transport activity: heterologous expression in yeast or Xenopus laevis oocytes, analysis of transport activity using either uptake of radiolabeled substrates or electrophysiology. To study the basis for differences in transport activity a modified gene shuffling technique called Synthetic Template Shuffling (STS) was developed in this project to generate libraries of chimeric transporters. Ancestral sequences reconstruction (using RAxML) is used to generate templates for STS. The current project also developed the use of fluorescent substrate uptake and fluorescence-activated cell sorting to select functional transporters from a gene-shuffled library. These approaches will be used to address the following objectives: 1) analysis of the basis for sucrose ultra-high affinity in the SUT family; 2) analysis of differences in amino acid specificity in the AAP family; and 3) functional analysis of AMTs from the basal land plant Marchantia polymorpha. Modified transporters will be tested for their effect on long-distance transport in plants by expression in the model plant Arabidopsis. This work will provide fundamental information necessary for future efforts to control carbon and nitrogen partitioning and sink strength in agricultural crops through modification of transport processes.
- Research Organization:
- Univ. of Minnesota, Minneapolis, MN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- FG02-07ER15886
- OSTI ID:
- 1581435
- Report Number(s):
- DOE-UMN-15886; UMN CON000000001587
- Country of Publication:
- United States
- Language:
- English
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