RESUMEN
KEY MESSAGE: Sucrose signaling pathways were rapidly induced in response to early iron deficiency in rice plants, and the change of sucrose contents in plants was essential for the activation of iron deficiency responses. Sucrose is the main product of photosynthesis in plants, and it functions not only as an energy metabolite but also a signal molecule. However, a few studies have examined the involvement of sucrose in mediating iron deficiency responses in rice. In this study, we found that the decrease in photosynthesis and total chlorophyll concentration (SPAD values) in leaves occurred at a very early stage under iron deficiency. In addition, the sucrose was increased in leaves but decreased in roots of rice plants under iron deficiency, and also the sucrose transporter (SUT) encoded genes' expression levels in leaves were all inhibited, including OsSUT1, OsSUT2, OsSUT3, OsSUT4, and OsSUT5. The carbohydrate distribution was changed under iron deficiency and sucrose might be involved in the iron deficiency responses of rice plants. Furthermore, exogenous application of sucrose or dark treatment experiments were used to test the hypothesis; we found that the increased endogenous sucrose would cause the repression of iron acquisition-related genes in roots, while further stimulated iron transport-related genes in leaves. Compared to the exogenous application of sucrose, the dark treatment had the opposite effects. All the above results highlighted the important role of sucrose in regulating the responses of rice plants to iron deficiency.