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The protein phosphatase 7 regulates phytochrome signaling in Arabidopsis.

ABSTRACT: The psi2 mutant of Arabidopsis displays amplification of the responses controlled by the red/far red light photoreceptors phytochrome A (phyA) and phytochrome B (phyB) but no apparent defect in blue light perception. We found that loss-of-function alleles of the protein phosphatase 7 (AtPP7) are responsible for the light hypersensitivity in psi2 demonstrating that AtPP7 controls the levels of phytochrome signaling. Plants expressing reduced levels of AtPP7 mRNA display reduced blue-light induced cryptochrome signaling but no noticeable deficiency in phytochrome signaling. Our genetic analysis suggests that phytochrome signaling is enhanced in the AtPP7 loss of function alleles, including in blue light, which masks the reduced cryptochrome signaling. AtPP7 has been found to interact both in yeast and in planta assays with nucleotide-diphosphate kinase 2 (NDPK2), a positive regulator of phytochrome signals. Analysis of ndpk2-psi2 double mutants suggests that NDPK2 plays a critical role in the AtPP7 regulation of the phytochrome pathway and identifies NDPK2 as an upstream element involved in the modulation of the salicylic acid (SA)-dependent defense pathway by light. Thus, cryptochrome- and phytochrome-specific light signals synchronously control their relative contribution to the regulation of plant development. Interestingly, PP7 and NDPK are also components of animal light signaling systems.

SUBMITTER: Genoud T

PROVIDER: S-EPMC2444027 | biostudies-literature | 2008 Jul

REPOSITORIES: biostudies-literature

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The protein phosphatase 7 regulates phytochrome signaling in Arabidopsis.

Genoud Thierry T Santa Cruz Marcela Treviño MT Kulisic Tea T Sparla Francesca F Fankhauser Christian C Métraux Jean-Pierre JP

PloS one 20080716 7

The psi2 mutant of Arabidopsis displays amplification of the responses controlled by the red/far red light photoreceptors phytochrome A (phyA) and phytochrome B (phyB) but no apparent defect in blue light perception. We found that loss-of-function alleles of the protein phosphatase 7 (AtPP7) are responsible for the light hypersensitivity in psi2 demonstrating that AtPP7 controls the levels of phytochrome signaling. Plants expressing reduced levels of AtPP7 mRNA display reduced blue-light induced ...[more]

PMID: 18628957

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Project description:The tyrosine kinase Fyn has two regulatory tyrosine residues that when phosphorylated either activate (Tyr(420)) or inhibit (Tyr(531)) Fyn activity. Within the central nervous system, two protein tyrosine phosphatases (PTPs) target these regulatory tyrosines in Fyn. PTP? dephosphorylates Tyr(531) and activates Fyn, while STEP (STriatal-Enriched protein tyrosine Phosphatase) dephosphorylates Tyr(420) and inactivates Fyn. Thus, PTP? and STEP have opposing functions in the regulation of Fyn; however, whether there is cross talk between these two PTPs remains unclear. Here, we used molecular techniques in primary neuronal cultures and in vivo to demonstrate that STEP negatively regulates PTP? by directly dephosphorylating PTP? at its regulatory Tyr(789). Dephosphorylation of Tyr(789) prevents the translocation of PTP? to synaptic membranes, blocking its ability to interact with and activate Fyn. Genetic or pharmacologic reduction in STEP61 activity increased the phosphorylation of PTP? at Tyr(789), as well as increased translocation of PTP? to synaptic membranes. Activation of PTP? and Fyn and trafficking of GluN2B to synaptic membranes are necessary for ethanol (EtOH) intake behaviors in rodents. We tested the functional significance of STEP61 in this signaling pathway by EtOH administration to primary cultures as well as in vivo, and demonstrated that the inactivation of STEP61 by EtOH leads to the activation of PTP?, its translocation to synaptic membranes, and the activation of Fyn. These findings indicate a novel mechanism by which STEP61 regulates PTP? and suggest that STEP and PTP? coordinate the regulation of Fyn. STEP61 , PTP?, Fyn, and NMDA receptor (NMDAR) have been implicated in ethanol intake behaviors in the dorsomedial striatum (DMS) in rodents. Here, we report that PTP? is a novel substrate for STEP61. Upon ethanol exposure, STEP61 is phosphorylated and inactivated by protein kinase A (PKA) signaling in the DMS. As a result of STEP61 inhibition, there is an increase in the phosphorylation of PTP?, which translocates to lipid rafts and activates Fyn and subsequent NMDAR signaling. The results demonstrate a synergistic regulation of Fyn-NMDAR signaling by STEP61 and PTP?, which may contribute to the regulation of ethanol-related behaviors. NMDA, N-methyl-D-aspartate; PTP?, receptor-type protein tyrosine phosphatase alpha; STEP, STriatal-Enriched protein tyrosine Phosphatase.

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The protein phosphatase 7 regulates phytochrome signaling in Arabidopsis.

Publications

The protein phosphatase 7 regulates phytochrome signaling in Arabidopsis.

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