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The protein phosphatases ATUNIS1 and ATUNIS2 regulated cell wall integrity in tip-growing cells.

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Franck Christina, Westermann Jens, Bürssner Simon, Lentz Roswitha, Lituiev Dmytro S, Boisson-Dernier Aurélien,
Project The Genetic and Molecular Basis of Gametogenesis and Maternal Effects in Arabidopsis
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Original article (peer-reviewed)

Journal The Plant Cell
Title of proceedings The Plant Cell
DOI 10.1105/tpc.18.00284


Fast tip-growing plant cells such as pollen tubes (PTs) and root hairs (RHs) require a robust coordination between their internal growth machinery and modifications of their extracellular rigid, yet extensible cell wall (CW). Part of this essential coordination is governed by members of the Catharanthus roseus receptor-like kinase1-like (CrRLK1L) subfamily of RLKs with FERONIA (FER) and its closest homologues, ANXUR1 (ANX1) and ANX2, controlling CW integrity during RH and PT growth, respectively. Recently, four Leucin-Rich-Repeat Extensins 8 to 11 (LRX8-11) were also shown to be important for CW integrity in PTs. We previously reported an anx1 anx2 suppressor screen in Arabidopsis that revealed MARIS (MRI) as a positive regulator of both FER- and ANX½-dependent CW integrity pathways. Here, we characterize a suppressor that exhibits a weak rescue of the anx1 anx2 PT bursting phenotype and a short RH phenotype. The corresponding suppressor mutation causes a D94N substitution in a Type One Protein Phosphatase we named ATUNIS1 (AUN1). We show that AUN1 and its closest homologue, AUN2, are nucleocytoplasmic negative regulators of tip-growth. Moreover, we demonstrate that AUN1D94N and AUN1H127A harbouring mutations in key amino acids of the conserved catalytic site of phosphoprotein phosphatases function as dominant amorphic variants that repress PT growth. Finally, genetic interaction studies using the hypermorph MRIR240C and amorph AUN1D94N dominant variants indicate that LRX8-11 and ANX½ function in distinct but converging pathways to fine-tune CW integrity during tip growth.