A PP6-type phosphatase holoenzyme directly regulates PIN phosphorylation and auxin efflux in Arabidopsis.
The directional transport of the phytohormone auxin depends on the phosphorylation status and polar localization of PIN-FORMED (PIN) auxin efflux proteins. While PINIOD (PID) kinase is directly involved in the phosphorylation of PIN proteins, the phosphatase holoenzyme complexes that dephosphorylate PIN proteins remain elusive. Here, we demonstrate that mutations simultaneously disrupting the function of Arabidopsis thaliana FyPP1 (for Phytochrome-associated serine/threonine protein phosphatase1) and FyPP3, two homologous genes encoding the catalytic subunits of protein phosphatase6 (PP6), cause elevated accumulation of phosphorylated PIN proteins, correlating with a basal-to-apical shift in subcellular PIN localization. The changes in PIN polarity result in increased root basipetal auxin transport and severe defects, including shorter roots, fewer lateral roots, defective columella cells, root meristem collapse, abnormal cotyledons (small, cup-shaped, or fused cotyledons), and altered leaf venation. Our molecular, biochemical, and genetic data support the notion that FyPP1/3, SAL (for SAPS DOMAIN-LIKE), and PP2AA proteins (RCN1 [for ROOTS CURL IN NAPHTHYLPHTHALAMIC ACID1] or PP2AA1, PP2AA2, and PP2AA3) physically interact to form a novel PP6-type heterotrimeric holoenzyme complex. We also show that FyPP1/3, SAL, and PP2AA interact with a subset of PIN proteins and that for SAL the strength of the interaction depends on the PIN phosphorylation status. Thus, an Arabidopsis PP6-type phosphatase holoenzyme acts antagonistically with PID to direct auxin transport polarity and plant development by directly regulating PIN phosphorylation.
Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Conecticut 06520-8104, USA.
Mingqiu
M
Dai
Chen
C
Zhang
Urszula
U
Kania
Fang
F
Chen
Qin
Q
Xue
Tyra
T
McCray
Gang
G
Li
Genji
G
Qin
Michelle
M
Wakeley
William
W
Terzaghi
Jianmin
J
Wan
Yunde
Y
Zhao
Jian
J
Xu
Jirí
J
Friml
Xing Wang
XW
Deng
Haiyang
H
Wang
D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D018548:Cotyledon / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D020035:Holoenzymes / Q000235:genetics / Q000378:metabolism; D007210:Indoleacetic Acids / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009708:Nucleotidases / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases; D010766:Phosphorylation; D063245:Plant Development; D018515:Plant Leaves / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D030821:Plants, Genetically Modified; D054648:Protein Phosphatase 2 / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D020035:Holoenzymes; D007210:Indoleacetic Acids; D026901:Membrane Transport Proteins; D009708:Nucleotidases; D010749:Phosphoprotein Phosphatases; D010744:Phosphoric Monoester Hydrolases; D054648:Protein Phosphatase 2; C116363:PIN1 protein, Arabidopsis; C117013:AT5G57090 protein, Arabidopsis; C449300:PIN3 protein, Arabidopsis; C451260:PIN4 protein, Arabidopsis; C472137:AtFyPP3 protein, Arabidopsis; C472136:FyPP1 protein, Arabidopsis; C478612:RCN1 protein, Arabidopsis; C053087:inositol-1,4-bisphosphate 1-phosphatase