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

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SUMMARY 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 NO 3 − and NH 4 + 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.