CALCIUM-DEPENDENT PROTEIN KINASE 32-mediated phosphorylation is essential for the ammonium transport activity of AMT1;1 in Arabidopsis roots

Author:

Qin De-Bin1,Liu Meng-Yuan1,Yuan Lixing2ORCID,Zhu Yun3,Li Xi-Dong1,Chen Li-Mei1,Wang Yi1,Chen Yi-Fang1,Wu Wei-Hua1,Wang Yang1ORCID

Affiliation:

1. State Key Laboratory of Plant Physiology and Biochemistry, College of Biological Sciences, China Agricultural University, Beijing, China

2. Department of Plant Nutrition, College of Resources and Environmental Sciences, China Agricultural University, Beijing, China

3. National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China

Abstract

Abstract Protein kinase-mediated phosphorylation modulates the absorption of many nutrients in plants. CALCIUM-DEPENDENT PROTEIN KINASES (CPKs) are key players in plant signaling to translate calcium signals into diverse physiological responses. However, the regulatory role of CPKs in ammonium uptake remains largely unknown. Here, using methylammonium (MeA) toxicity screening, CPK32 was identified as a positive regulator of ammonium uptake in roots. CPK32 specifically interacted with AMMONIUM TRANSPORTER 1;1 (AMT1;1) and phosphorylated AMT1;1 at the non-conserved serine residue Ser450 in the C-terminal domain. Functional analysis in Xenopus oocytes showed that co-expression of CPK32 and AMT1;1 significantly enhanced the AMT1;1-mediated inward ammonium currents. In transgenic plants, the phosphomimic variant AMT1;1S450E, but not the non-phosphorylatable variant AMT1;1S450A, fully complemented the MeA insensitivity and restored high-affinity 15NH4+ uptake in both amt1;1 and cpk32 mutants. Moreover, in the CPK32 knockout background, AMT1;1 lost its ammonium transport activity entirely. These results indicate that CPK32 is a crucial positive regulator of ammonium uptake in roots and the ammonium transport activity of AMT1;1 is dependent on CPK32-mediated phosphorylation.

Funder

National Natural Science Foundation of China

National Key Research and Development Program of China

Chinese Universities Scientific Fund

Publisher

Oxford University Press (OUP)

Subject

Plant Science,Physiology

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