The role of Vacuolar Hexose Exporters during Stress Response and Development

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Subcellular sugar partitioning in plants is strongly regulated in adaptation to developmental cues and external conditions. We have identified the vacuolar glucose exporter ERD6-like 6 (ERDL6), which has a significant impact on cellular glucose homeostasis and composition of seed reserves. ERDL6 expression is induced in response to factors that activate vacuolar glucose pools and reduced during conditions that trigger glucose accumulation in the vacuole. Accordingly, erdl6 mutants have elevated vacuolar glucose levels and glucose flux across the tonoplast is impaired under stress conditions. In the proposed funding period we will elucidate further characteristics of ERDL6 including the mode of transport activity as well as its role during response to other stresses (osmotic/drought stress, freezing tolerance, light limitation) and during development (pollen maturation/germination, cell wall composition) with respect to its transcriptional and post-transcriptional regulation (phosphorylation). In addition, we will address the role of other ERDLs in hexose export from the vacuole by high-throughput growth phenotyping of erdl mutants, analysis of multiple erdl-KOs for enhanced impairment of vacuolar glucose partitioning, as well as testing complementation of the described erdl6-KO effects by other ERDLs. Combinatorial mutants with tmts and vha2,3 will help to explore the functional network of hexose exporters and other types of tonoplast transporters, which regulates vacuolar sugar partitioning and determines the plants performance during stress response and development.