A role for calcium-dependent protein kinases in differential CO - and ABA-controlled stomatal closing and low CO -induced stomatal opening in Arabidopsis.

Low concentrations of CO cause stomatal opening, whereas [CO ] elevation leads to stomatal closure. Classical studies have suggested a role for Ca and protein phosphorylation in CO -induced stomatal closing. Calcium-dependent protein kinases (CPKs) and calcineurin-B-like proteins (CBLs) can sense and translate cytosolic elevation of the second messenger Ca into specific phosphorylation events.

Plasma membrane calcineurin B-like calcium-ion sensor proteins function in regulating primary root growth and nitrate uptake by affecting global phosphorylation patterns and microdomain protein distribution.

The collective function of calcineurin B-like (CBL) calcium ion (Ca ) sensors and CBL-interacting protein kinases (CIPKs) in decoding plasma-membrane-initiated Ca signals to convey developmental and adaptive responses to fluctuating nitrate availability remained to be determined. Here, we generated a cbl-quintuple mutant in Arabidopsis thaliana devoid of these Ca sensors at the plasma membrane and performed comparative phenotyping, nitrate flux determination, phosphoproteome analyses, and studies of membrane domain protein distribution in response to low and high nitrate availability. We observed that CBL proteins exert multifaceted regulation of primary and lateral root growth and nitrate fluxes.

Golgi α1,4-fucosyltransferase of Arabidopsis thaliana partially localizes at the nuclear envelope.

We analyzed plant-derived α1,4-fucosyltransferase (FucTc) homologs by reporter fusions and focused on representatives of the Brassicaceae and Solanaceae. Arabidopsis thaliana AtFucTc-green fluorescent protein (GFP) or tomato LeFucTc-GFP restored Lewis-a formation in a fuctc mutant, confirming functionality in the trans-Golgi. AtFucTc-GFP partly accumulated at the nuclear envelope (NE) not observed for other homologs or truncated AtFucTc lacking the N-terminus or catalytic domain.

Two spatially and temporally distinct Ca signals convey Arabidopsis thaliana responses to K deficiency.

In plants, potassium (K ) homeostasis is tightly regulated and established against a concentration gradient to the environment. Despite the identification of Ca -regulated kinases as modulators of K channels, the immediate signaling and adaptation mechanisms of plants to low-K conditions are only partially understood. To assess the occurrence and role of Ca signals in Arabidopsis thaliana roots, we employed ratiometric analyses of Ca dynamics in plants expressing the Ca reporter YC3.

Calredoxin represents a novel type of calcium-dependent sensor-responder connected to redox regulation in the chloroplast.

Calcium (Ca(2+)) and redox signalling play important roles in acclimation processes from archaea to eukaryotic organisms. Herein we characterized a unique protein from Chlamydomonas reinhardtii that has the competence to integrate Ca(2+)- and redox-related signalling. This protein, designated as calredoxin (CRX), combines four Ca(2+)-binding EF-hands and a thioredoxin (TRX) domain.

Nitrate sensing and uptake in Arabidopsis are enhanced by ABI2, a phosphatase inactivated by the stress hormone abscisic acid.

Living organisms sense and respond to changes in nutrient availability to cope with diverse environmental conditions. Nitrate (NO3-) is the main source of nitrogen for plants and is a major component in fertilizer. Unraveling the molecular basis of nitrate sensing and regulation of nitrate uptake should enable the development of strategies to increase the efficiency of nitrogen use and maximize nitrate uptake by plants, which would aid in reducing nitrate pollution.

Visualization and translocation of ternary Calcineurin-A/Calcineurin-B/Calmodulin-2 protein complexes by dual-color trimolecular fluorescence complementation.

Fluorescence complementation (FC) techniques are expedient for analyzing bimolecular protein-protein interactions. Here we aimed to develop a method for visualization of ternary protein complexes using dual-color trimolecular fluorescence complementation (TriFC). Dual-color TriFC combines protein fragments of mCherry and mVenus, in which a scaffold protein is bilaterally fused to C-terminal fragments of both fluorescent proteins and combined with potential interacting proteins fused to an N-terminal fluorescent protein fragment.

Site- and kinase-specific phosphorylation-mediated activation of SLAC1, a guard cell anion channel stimulated by abscisic acid.

Under drought stress, abscisic acid (ABA) triggers closure of leaf cell pores called stomata, which are formed by two specialized cells called guard cells in plant epidermis. Two pathways downstream of ABA stimulate phosphorylation of the S-type anion channels SLAC1 (slow anion channel associated 1) and SLAH3 (SLAC1 homolog 3), which causes these channels to open, reducing guard cell volume and triggering stomatal closure. One branch involves OST1 (open stomata 1), a calcium-independent SnRK2-type kinase, and the other branch involves calcium-dependent protein kinases of the CPK (calcium-dependent protein kinase) family.

Calcium-dependent modulation and plasma membrane targeting of the AKT2 potassium channel by the CBL4/CIPK6 calcium sensor/protein kinase complex.

Potassium (K(+)) channel function is fundamental to many physiological processes. However, components and mechanisms regulating the activity of plant K(+) channels remain poorly understood. Here, we show that the calcium (Ca(2+)) sensor CBL4 together with the interacting protein kinase CIPK6 modulates the activity and plasma membrane (PM) targeting of the K(+) channel AKT2 from Arabidopsis thaliana by mediating translocation of AKT2 to the PM in plant cells and enhancing AKT2 activity in oocytes.