OsSWEET11 modulates rice adventitious root development by influencing cytokinin levels through sucrose transport under low nitrogen

Plants enhance sucrose transport to the roots under nitrogen-limited conditions, which is crucial for root development. However, the mechanisms by which enhanced sucrose transport influences root development remain unclear under low nitrogen (LN). Sucrose concentrations were measured in wild type (WT) rice under different nitrogen conditions, showing decreased levels in shoots but increased levels in roots under LN, with upregulated expression of SUGAR WILL EVENTUALLY BE EXPORTED TRANSPORTER11 (OsSWEET11) in the roots and shoot base. The role of OsSWEET11-mediated sucrose transport in regulating adventitious root (AR) development in rice was investigated under LN. OsSWEET11 knockout mutants under LN exhibited a reduced AR number compared to the WT, leading to lower nitrogen uptake and grain yield in hydroponic and field experiments. Compared to the WT, the mutants had higher sucrose levels in leaf blades and sheaths, but lower levels in the shoot base, roots, and phloem exudates under LN. However, sucrose application did not compensate for the AR phenotype in OsSWEET11 mutants. Cytokinin levels were reduced under LN in the OsSWEET11 mutants, and the mutants exhibited lower cytokinin levels than WT when sucrose was applied in addition to different nitrogen levels. Exogenous application of 6-BA compensated for the reduced AR number in OsSWEET11 mutants. Gene expression analysis showed that OsSWEET11 was induced by OsDOF11 under LN, and OsDOF11 knockout mutants exhibited a reduced AR number, which was compensated by exogenous application of 6-BA. These findings demonstrate that, under LN, knockout of OsSWEET11 inhibits AR development by reducing cytokinin levels through sucrose transport, which indirectly affects nitrogen uptake and yield.