Spotted leaf 11 (SPL11) contributes plant growth and adaptation to nitrogen limitation in rice

Abstract The ubiquitin-proteasome system (UPS) involves in many plant processes and responses to abiotic and biotic stresses. SPL11 (spotted leaf 11, SPL11) encoding a U-box E3 ligase negatively regulates flowering, plant defense and lesion-mimic phenotype. Our previous study discovered the up-regulation of SPL11 under limited nitrogen (LN) condition. However, it is little known that whether SPL11 mediates plant growth and adaptation to LN stress. Here, we further investigated the growth including height, biomass accumulation, nitrate content and NRT gene expression in spl11 mutant and SPL11 OX plants under HN and LN conditions. The spl11 mutant showed impaired growth compared with the wild type (WT) IR64 regardless of nitrogen supply conditions. SPL11 OX plants showed increasing growth compared with the WT TP309 only under HN but not LN condition. The expression of NRT genes supported the above phenotypes. In addition, under LN condition, the spl11 mutant showed earlier and severer senescence than the WT IR64, while no significant difference was found in the other three tested varieties. All these results suggested that SPL11 is essential to plant growth, adaption to LN stress, and repression of LN-caused early senescence. Moreover, the E3 ligase activity of SPL11 possibly inhibited by LN stress may also be required for the above regulatory functions. This study unveils novel regulatory functions of SPL11 on plant growth, adaption to LN stress and LN-caused early senescence.