Kun Yue, Priyanka Sandal, Elisabeth L. Williams, Evan Murphy, Elisabeth Stes, Natalia Nikonorova, Priya Ramakrishna, Nathan Czyzewicz, Laura Montero-Morales, Robert Kumpf, Zhefeng Lin, Brigitte van de Cotte, Mudassar Iqbal, Michiel Van Bel, Eveline Van De Slijke, Matthew R. Meyer, Astrid Gadeyne, Cyril Zipfel, Geert De Jaeger, Marc Van Montagu, Daniël Van Damme, Kris Gevaert, A. Gururaj Rao, Tom Beeckman, and Ive De Smet

Significance

Plant growth and development are mediated through a wide range of proteins, including receptor kinases and phosphatases. The receptor kinase ARABIDOPSIS CRINKLY 4 (ACR4) is part of a mechanism controlling formative cell divisions in the Arabidopsis root. However, the regulation of ACR4 signaling and how it affects cell divisions remains completely unknown. We discovered that ACR4 phosphorylates the PROTEIN PHOSPHATASE 2A-3 (PP2A-3) catalytic subunit of the PP2A phosphatase holoenzyme and that PP2A dephosphorylates ACR4. These data exposed a tightly regulated point in the associated biochemical network regulating formative cell divisions in plant roots.

Abstract

In plants, the generation of new cell types and tissues depends on coordinated and oriented formative cell divisions. The plasma membrane-localized receptor kinase ARABIDOPSIS CRINKLY 4 (ACR4) is part of a mechanism controlling formative cell divisions in the Arabidopsis root. Despite its important role in plant development, very little is known about the molecular mechanism with which ACR4 is affiliated and its network of interactions. Here, we used various complementary proteomic approaches to identify ACR4-interacting protein candidates that are likely regulators of formative cell divisions and that could pave the way to unraveling the molecular basis behind ACR4-mediated signaling. We identified PROTEIN PHOSPHATASE 2A-3 (PP2A-3), a catalytic subunit of PP2A holoenzymes, as a previously unidentified regulator of formative cell divisions and as one of the first described substrates of ACR4. Our in vitro data argue for the existence of a tight posttranslational regulation in the associated biochemical network through reciprocal regulation between ACR4 and PP2A-3 at the phosphorylation level.

See: http://www.pnas.org/content/113/5/1447.abstract.html?etoc

PNAS February 2, 2016; vol. 113 no. 5: 1447–1452

Fig. 1. ACR4 interacts with PP2A-3. (A) Schematic representation of ACR4 with key domains and regions used for protein–protein interaction studies. (B) In vitro GST pull-down experiment using GST:PP2A-3 and MBP:ACR4^ICD according to indicated combinations (+). PP2A-3 and ACR4^ICD were detected by Western blotting with anti-GST and anti-MBP antibodies, respectively. (C) In planta YFP pull-down experiment using ACR4:YFP:HA and FLAG:PP2A-3 transiently coexpressed in tobacco leaves by Agrobacterium infiltration according to indicated combinations (+). PP2A-3 and ACR4 were detected by Western blotting with anti-FLAG and anti-HA antibodies, respectively.