SnRK2.10 in apple positively regulates the nitrogen use efficiency via modulating the nitrogen uptake

Sucrose non-fermentation-1-related protein kinase 2 (SnRK2) family members play key roles in plant adaptation to environmental stress. In this study, low nitrogen (N) stress induced the expression of SnRK2.10, which mitigated the adverse effects of N deficiency in apple plants. SnRK2.10-overexpressing (OE) plants showed enhanced growth and higher nitrogen use efficiency (NUE), whereas SnRK2.10-silenced (Ri) plants exhibited more severe growth inhibition and reduced NUE, compared with the wild-type (WT) plants under low N conditions. The transcriptomic and proteomic analyses indicated that SnRK2.10 regulates N metabolism and transport. It physically interacted with the nitrate transporter NRT2.5 and the ammonium transporter AMT1.1. Consistently, OE plants displayed higher NO₃ ^- and NH₄ ⁺ uptake rates than WT and Ri plants under low N stress. Functional analyses using transgenic apple lines with different expression levels of NRT2.5 or AMT1.1 demonstrated that both transporters positively regulate growth and NUE in apple plants' response to low N stress. Co-expression of SnRK2.10 with either NRT2.5 or AMT1.1 effectively altered plant growth under low N stress. Collectively, these results indicate that SnRK2.10 positively regulates plant growth and NUE under low N stress, probably by promoting N uptake through direct interaction with key N transporters.