Effects of ATSU4 on root development under high sucrose stress

Sucrose is the principal product of photosynthesis used for the distribution of assimilated carbon in plants. Source-to-sink transport of sucrose is one of the major determinants of plant growth. However, the role of AtSUC4, a member of sucrose transporter family, was undervalued in this process due to its weak expression in sink organ during seedling. In our study, the root of atsuc4 knockout lines accumulated less sucrose compared with wild-type (WT) plants with the 4% and 6% sucrose supplementation. Meanwhile, the main root length of the mutants was significantly longer than that of the WT, including the meristem region. While, this phenotype could not be imitated by external application of glucose or mannitol. In addition, comparative transcriptome between WT and atsuc4 mutant showed that the pathways of sucrose transport, synthesis and degradation, T6P signals, ABA signals and auxin signals were significantly changed. Taken together, we conclude that the deficiency of AtSUC4, on the one hand, reduces the uptake of sucrose, on the other hand, as a signal, was involved in plant response to high sucrose stress.