(800-160) Knockout of winter biased SUTs in poplar highlights the involvement of vacuolar sucrose transporter on biomass accrual, winter protection, and environmental sensing
Graduate Student University of Georgia ATHENS, Georgia
Body of Abstract: Perennial trees experience dynamic fluctuations between active growth and dormancy that are associated with carbohydrate allocation and remobilization. As the need for carbohydrates changes to support the perennial growth cycle, so does the expression of genes involved in various carbohydrate mobilization processes. The poplar genome contains five sucrose transporter (SUT) genes with contrasting seasonal expression patterns. Among them, the single-copy SUT4 and the SUT5/SUT6 genome duplicates all exhibit winter biased expression, while the SUT1/SUT3 paralogs display summer biased expression. The contrasting expression hints at seasonal specific roles amongst the gene family members. Here, we generated CRISPR knockout mutants for the winter biased SUTs in Populus tremula x alba and investigated their seasonal growth response through a multi-year field trial. Subtle growth differences were observed between the sut mutants and controls in the first growing season, but stem diameter and height were reduced in the sut4 trees following growth resumption. The sut4 mutants showed phenological changes, as both fall leaf senescence and spring bud flush were altered which resulted in reduced leaf area duration. The sut4 mutants also exhibited altered sugar partitioning and reductions of oligosaccharides associated with cold tolerance. These field phenotypes are striking considering that prior characterization of greenhouse grown sut4 mutants displayed subtle, if any, differences in growth. Interestingly, perturbation of winter biased SUT5 and SUT6 had minimal impact on tree growth or seasonal phenology. These results suggest an important role for sucrose transporters on environmental sensing, leaf area duration, and protective metabolism in winter stems of woody perennials.