MdERDL6-mediated glucose efflux to the cytosol promotes sugar accumulation in the vacuole through up-regulating TSTs in apple and tomato

Significance Sugar transport across membranes is essential for maintaining cellular sugar homeostasis and metabolic balance in plant cells. However, it remains unclear how this process is regulated among different classes of sugar transporters. Here, we identified an apple tonoplast H + /glucose symporter, MdERDL6-1, that exports glucose to cytosols to up-regulate the expression of H + /sugar antiporter genes TST1 and TST2 to import sugars from cytosol to vacuole for accumulation to high concentrations in apples and tomatoes. The findings provide insights into the regulatory mechanism underlying sugar exchange between cytosol and vacuole.