TY - JOUR

T1 - A plastid nucleoside kinase is involved in inosine salvage and control of purine nucleotide biosynthesis

AU - Chen, Xiaoguang

AU - Kim, Sang Hoon

AU - Rhee, Sangkee

AU - Witte, Claus Peter

N1 - Funding Information: X.C. was funded by the Chinese Scholarship Council (PhD fellowship 201703250066) and a fellowship of the Institute of Plant Nutrition of LUH. The research was supported by grants of the Deutsche Forschungsgemeinschaft to C.P.W. (WI3411/7-1; WI3411/8-1) and INST 187/741-1 FUGG. Acknowledgments: We thank Andre ́ Specht and Hildegard Tho ̈lke for technical assistance and Markus Niehaus and Mingjia Chen for general support. We also thank Marco Herde and Henryk Straube for critical discussions.

PY - 2023/1/2

Y1 - 2023/1/2

N2 - In nucleotide metabolism, nucleoside kinases recycle nucleosides into nucleotides-a process called nucleoside salvage. Nucleoside kinases for adenosine, uridine, and cytidine have been characterized from many organisms, but kinases for inosine and guanosine salvage are not yet known in eukaryotes and only a few such enzymes have been described from bacteria. Here we identified Arabidopsis thaliana PLASTID NUCLEOSIDE KINASE 1 (PNK1), an enzyme highly conserved in plants and green algae belonging to the Phosphofructokinase B family. We demonstrate that PNK1 from A. thaliana is located in plastids and catalyzes the phosphorylation of inosine, 5-aminoimidazole-4-carboxamide-1-β-d-ribose (AICA ribonucleoside), and uridine but not guanosine in vitro, and is involved in inosine salvage in vivo. PNK1 mutation leads to increased flux into purine nucleotide catabolism and, especially in the context of defective uridine degradation, to over-accumulation of uridine and UTP as well as growth depression. The data suggest that PNK1 is involved in feedback regulation of purine nucleotide biosynthesis and possibly also pyrimidine nucleotide biosynthesis. We additionally report that cold stress leads to accumulation of purine nucleotides, probably by inducing nucleotide biosynthesis, but that this adjustment of nucleotide homeostasis to environmental conditions is not controlled by PNK1.

AB - In nucleotide metabolism, nucleoside kinases recycle nucleosides into nucleotides-a process called nucleoside salvage. Nucleoside kinases for adenosine, uridine, and cytidine have been characterized from many organisms, but kinases for inosine and guanosine salvage are not yet known in eukaryotes and only a few such enzymes have been described from bacteria. Here we identified Arabidopsis thaliana PLASTID NUCLEOSIDE KINASE 1 (PNK1), an enzyme highly conserved in plants and green algae belonging to the Phosphofructokinase B family. We demonstrate that PNK1 from A. thaliana is located in plastids and catalyzes the phosphorylation of inosine, 5-aminoimidazole-4-carboxamide-1-β-d-ribose (AICA ribonucleoside), and uridine but not guanosine in vitro, and is involved in inosine salvage in vivo. PNK1 mutation leads to increased flux into purine nucleotide catabolism and, especially in the context of defective uridine degradation, to over-accumulation of uridine and UTP as well as growth depression. The data suggest that PNK1 is involved in feedback regulation of purine nucleotide biosynthesis and possibly also pyrimidine nucleotide biosynthesis. We additionally report that cold stress leads to accumulation of purine nucleotides, probably by inducing nucleotide biosynthesis, but that this adjustment of nucleotide homeostasis to environmental conditions is not controlled by PNK1.

UR - http://www.scopus.com/inward/record.url?scp=85145425054&partnerID=8YFLogxK

U2 - 10.1093/plcell/koac320

DO - 10.1093/plcell/koac320

M3 - Article

C2 - 36342213

AN - SCOPUS:85145425054

VL - 35

SP - 510

EP - 528

JO - The plant cell

JF - The plant cell

SN - 1040-4651

IS - 1

ER -